Leptospirosis in NZ - Best Practice recommendations vaccine use to prevent human exposure.

Leptospirosis in NZ - Best Practice recommendations vaccine use to prevent human exposure.
Leptospirosis in New Zealand – Best Practice Recommendations
for the use of vaccines to prevent human exposure
A Report by Massey University Prepared for the
Zealand Veterinary Association
June 2012
Authors: Cord Heuer, Jackie Benschop, Leslie Stringer, Julie Collins-Emerson, Juan
Sanhueza, and Peter Wilson
Institute of Veterinary, Animal and Biomedical Sciences, Massey University
1
Contents
Executive Summary.......................................................................................................................... 3
1. Objectives................................................................................................................................. 6
1.1. Search Methodology ................................................................................................................ 6
2. Introduction ............................................................................................................................. 7
2.1 Motivation................................................................................................................................ 7
2.2 The international human leptospirosis context ....................................................................... 8
2.3 Human leptospirosis in New Zealand ...................................................................................... 9
3. Hosts – pathogen relationships in NZ .................................................................................... 11
3.1 Host species and Leptospira serovars in NZ........................................................................... 11
3.2 Transmission routes ............................................................................................................... 14
3.3 Conclusions: host/pathogen relationships ............................................................................ 15
4. Environmental effects ............................................................................................................ 15
4.1 Introduction ........................................................................................................................... 15
4.2 The New Zealand environment and Leptospirosis ................................................................. 17
5. Farm management ................................................................................................................. 20
6. Production outcomes ............................................................................................................. 26
6.1 Conclusions on production outcomes ................................................................................... 29
7. History of vaccine use in New Zealand .................................................................................. 29
8. Vaccine label claims and recommendations.......................................................................... 30
9. Host immune response after exposure ................................................................................. 33
9.1 Background ............................................................................................................................ 33
10. Evidence of vaccine efficacy to prevent urinary shedding .................................................... 39
10.5 Vaccination of dams to protect offspring .............................................................................. 42
10.6 Interference by maternally derived antibody (MDA) with vaccination ................................. 43
10.7 Duration of immunity............................................................................................................. 47
10.8 Conclusions on vaccine efficacy to prevent shedding ........................................................... 48
11 Required information (future research) ................................................................................ 48
12 Guideline for Best-Practice recommendations for vaccination ............................................. 50
13. References.............................................................................................................................. 53
Annex I: .......................................................................................................................................... 60
Best practice recommendations – DAIRY ...................................................................................... 60
Best practice recommendations – SHEEP ...................................................................................... 62
Best practice recommendations – BEEF ........................................................................................ 64
Best practice recommendations – DEER ........................................................................................ 65
Annex II: List of vaccine efficacy studies where the outcome was urine shedding ....................... 66
Annex III: List of commercially available vaccines (July 2012) ....................................................... 79
2
Executive Summary
1.
Motivation: This review of Best-Practice recommendations for the use of vaccines for
immunising livestock (dairy and beef cattle, sheep, deer) against leptospirosis was
instigated by NZVA’s Dairy Cattle Veterinary (DCV) Special Interest Branch and Leptosure.
The principle motivation for this move was a general uncertainty about the optimum age of
first vaccination, timing of boosters. Product label recommendations currently prescribe
different vaccination regimens. It was anticipated that the outcome of this review would
form the basis for the development of accepted standards to be widely disseminated in the
veterinary community.
2.
Aims and methodology: Massey University was therefore contracted to conduct a
systematic review of the literature relating to leptospirosis vaccination in cattle, sheep and
deer. Aims included a review of vaccine efficacy in relation to antibody in colostrum, to the
duration of colostral immunity, and to the age at first natural challenge. After further
consultation with the funders, the aims were extended to cover the epidemiology of
leptospirosis in New Zealand, mechanisms and measurement of host immune response and
the integration of vaccination into seasonal farm management. Included is a summary of
the gaps in current knowledge. The Best-Practice recommendations contained in this
report are thus limited to the currently available knowledge.
3.
Importance of leptospirosis: Concerns relate to both human and animal infections. Despite
numerous investigations and control efforts, leptospirosis is still the most important
zoonosis in New Zealand. There are around 100 notified cases per year, but the number of
illness episodes due to leptospirosis is estimated to be 40-50 times higher. Moreover, the
ecology of leptospirosis appears to be undergoing change, possibly driven by more
intensive farming systems and subtle climate change. Clinical disease was common in dairy
prior to adoption of vaccination in 1990s. Unvaccinated sheep, beef and deer herds are at
risk of clinical disease outbreaks, which in humid periods may manifest with mortality rates
up to 20%. Production effects have recently been quantified for deer (growth,
reproduction) and beef cattle (abortion).
4.
Vaccine efficacy: the key point to take from efficacy studies in dairy cattle carried out
within the past 20 years is that mono- or bivalent leptospirosis vaccines alike were efficient
for preventing urine shedding (80-100% efficacy) when vaccination preceded challenge.
However, a 2011-study with 100% vaccine efficacy based on urine culture, found 6/8
vaccinates and 4/4 controls as urine-PCR-positive. Thus, a low level of shedding postvaccination in dairy herds cannot be ruled out. There are also unpublished data suggesting
a lower immune response from vaccines containing a large number of (clostridial) antigens.
Another caveat is that vaccination works well as long as no prior challenge has occurred:
two studies found continued shedding (cattle, deer) in both vaccinates and controls when
urinary shedding was present at the time of first vaccination. The protective effect of
vaccination against infection and subsequent shedding was shown to last at least for 13
months.
5.
Maternally derived antibody (MDA): the mean half-life of IgG1, the main immune-globulin
comprising MDA, was 18 days in individual calves. MDA in bovine calves, measured by the
microscopic agglutination test (MAT), was shown experimentally to convey protective
immunity until challenge at 4 weeks of age. MAT in new-borne calves was observed to have
waned off almost completely up to 100 days of age. Based on the rate of decay to become
zero at 100 days, about 80% calves have no measurable antibody after 50 days of age, thus
3
at group-level, calves may be regarded as susceptible from about 7 weeks of age if a
protective level of MDA was present in all calves at birth. Under commercial farming
conditions however, not all dams transmit a protective level of MDA through colostrum
and only about 50% calves ingest sufficient colostrum within the first 12 hours of birth.
Consequently, passive immunity at group-level is unlikely to be sustained until 7 weeks of
age in most herds. Hence, most calves are likely to become susceptible to infection earlier
than that. No information is available about the relative efficiency of MDA derived from
vaccination compared to that derived from natural challenge of dams. Assuming no
difference exists and based on the MDA decay described above, the latest age at grouplevel at which calves, lambs or fawns become susceptible to infection under field
conditions, may therefore be around 4-6 weeks in situations where dams were vaccinated
(dairy) or were subjected to high natural challenge (beef, deer, sheep).
6.
Interference by MDA with vaccine-induced immunity: In the absence of MDA, vaccination
against Leptospira is effective as early as 4 weeks of age. No conclusive evidence exists in
any species about MDA reducing vaccine efficacy: one experimental infection rendered
vaccination in the presence of MAT antibody ineffective, another found no interference.
Since both studies were based on low numbers of calves and trial conditions were highly
artificial, little credible inference can be derived from these disparate outcomes about MDA
interference with vaccination under commercial farming conditions. Since there is doubt, a
conservative view appears advisable for the purpose of Best-Practice recommendations,
pending research to clarify this issue. Hence interference may be assumed to exist until
conclusive evidence is presented to the contrary. Consequently, accepting a MDA decay by
100 days, the maximum age at which MDA may inhibit vaccine efficacy in about 20% of a
calf mob is 7 weeks of age (point 5 above), and under commercial farming conditions may
be a maximum of 4-6 weeks of age. There was no MDA interference with serological
response to vaccination of deer at approximately 100 days of age.
7.
Age at first vaccination: no vaccination is required for lambs or deer for slaughter, or for
bobby calves (dairy). However, all other ages and types of sheep, dairy, beef and deer
should be vaccinated regularly. Assuming that MDA reduces vaccine efficacy and that most
offspring may have lost MDA by 4-6 weeks of age, and assuming further that the age
spread of young stock to be used for replacement is 6 weeks (+/- 3w of the average), we
recommend an average mob age at first vaccination of 7 weeks (3+4w). This would be the
earliest average age at which the first of two successive vaccinations should be applied.
Under commercial farming conditions this translates to 10 weeks (6+4w) after the start of
seasonal calving/lambing as the earliest time to start vaccinating offspring. The advice for
the latest age at which calves should have completed their first vaccination course is based
on reports about natural challenge at 3-6 months in high risk environments. Thus, best
practice advice is to complete a course of two vaccinations (4-6 week interval between
injections) before the oldest calf/lamb has reached 6 months of age. For commercial
farming conditions, this would typically be 18 weeks after the start of seasonal
calving/lambing as the latest time to start vaccinating offspring. These recommendations
are illustrated in Figure 12.1.
8.
Differentiating the level of natural challenge: under dry environmental conditions and
where access to potentially contaminated water does not exist or when whole-herd/flock
vaccination has been consistently applied for a number of years, the risk of natural
challenge should be low. On the contrary, farms where unvaccinated herds or flocks with
access to contaminated water (flooded pasture), or where replacement stock is returning
4
from locations where they were grazed at unknown or high risk, may be at a high risk of
natural challenge. Typical examples for the former may be continuously vaccinating and
closed dairy herds (low risk), and for the latter may be deer or beef herds, or sheep flocks
on wet soils (high risk) or downstream of infected herds/flocks. Given that almost all beef
cattle and deer herds, and sheep flocks in New Zealand have evidence of infection, most of
such farms may be in the high-risk category.
a. In high risk environments such as most beef, deer and sheep farming conditions, a longterm vaccination plan should be considered. Here the initial vaccination of young stock
is best applied early, hence about 4-6 weeks of age with a booster at 8-10 weeks. This
should be followed by another booster 6 months later or at the time of the annual
whole-herd booster. After 2-3 years, such herds and flocks may be regarded as having
acquired a low-risk status. Consequently, the age of first vaccination may follow
guidelines for low risk environments;
b. In low-risk environments such as herds or flocks with a history of continued vaccination,
new-borns may receive their first vaccination at 4-12 weeks of age. The first course of
vaccination should be completed as early born calves/lambs/fawns are 6 months old.
For continued immunity, these new-borns should be re-vaccinated at the time of the
annual whole herd/flock booster vaccination.
c. We present another point for discussion that has so far not been considered in any of
the vaccine label claims: If dams were vaccinated after parturition in a low risk
environment, vaccine induced MDA may be regarded as absent and thus vaccine
efficacy would not be impaired by vaccine induced MDA. In that situation, the first
vaccination may be scheduled within the first month of birth, or in terms of seasonal
management, at the end of calving/lambing. Hence, applying the annual vaccine booster
to cows AFTER parturition and starting to vaccinate new-born calves as early as
practically feasible, may be an advisable practice.
9.
Required knowledge: The principal knowledge deficit identified by this project is the
impact of MDA on vaccination response and immunity in offspring in relation to timing of
first vaccination in cattle and sheep. Robust recommendations for best practice in terms of
optimum age at first vaccination in those species cannot be given until this question is
resolved. Additionally, no information is currently available about the occupational risk of
leptospirosis among farmers, their families, veterinarians and livestock workers. More
knowledge is also required about the optimal age at first vaccination and duration of
immunity under commercial farming conditions. Moreover, robust evidence is required
about the frequency and the quantity of shedding in vaccinated herds or flocks. This review
therefore identified the following knowledge gaps:
a. There is a pressing need for large scale field trials of vaccine efficacy in herds
and flocks, comparing vaccinated with unvaccinated dams in conjunction with
vaccinating offspring at various ages (1, 3, 6 months) in endemic herds/flocks.
b. The overall risk of and source for infection of farmers, livestock workers and
veterinarians is currently unknown. This includes wildlife sources such as
rodents, possums, hedgehogs, feral pigs and rabbits. This would include
attention to host reservoirs for serovar Ballum. An observational study
approach is suggested.
c. A recent pilot study of shedding in dairy cows raises the question whether PCR
positive urine is infectious, i.e. contains live Leptospira at sufficiently high dose.
Given the zoonotic potential of Leptospira, a nationwide prevalence study of
urine shedding, serovars involved and an accurate account of vaccination
practices in dairy herds is proposed.
5
1. Objectives
The report presents a systematic literature review to evaluate the following key issues:
The past and present situation of the epidemiology of leptospirosis in New Zealand in
relation to the use of vaccines in livestock;
The loss of production due to leptospirosis infection and the proportion of the loss
preventable by vaccination;
Uncertainties about current recommendations for the use of leptospirosis vaccines in
New Zealand with special consideration of:
o The type and measurement of the immune response to infection or vaccination;
o The measurement of vaccine efficacy;
o The likely presence and interference of a maternally derived immune response;
o The age at first vaccination to prevent urinary shedding;
o The effect of vaccination before and after natural exposure;
o The duration of vaccine induced immunity;
o Environmental and management factors interacting with the response to
vaccination;
Based on the results, the report subsequently derives best practice recommendations for the
use of leptospirosis vaccines in:
Dairy cattle;
Beef cattle;
Deer; and
Sheep.
1.1. Search Methodology
Pubmed and the Web of Knowledge data bases were searched using the following key words.
[species] AND [vaccination] AND [outcome], where:
Species:
- Lepto* OR Weil;
- Cattle OR Bovine,
- Deer OR Cervine,
- Sheep OR Ewe*,
- Human OR People OR Worker* OR Farmer*
Vaccination:
- Vacc* OR Prophy OR Immun* OR Protect*
Outcome:
- Efficacy OR Effecti* OR Shedd* OR Serolog* OR Antibod*.
Firstly, titles and abstracts of all returned articles were scanned to select relevant articles by one
author (JS). A relevant article was defined as one that contained information that would inform
the report as scoped above. Unpublished literature and data from Massey studies and from
New Zealand pharmaceutical companies (MSD Animal Health, Pfizer Animal Health and Virbac
Animal Health) also formed a substantial part of the review process.
6
2. Introduction
2.1 Motivation
Leptospirosis continues to place a significant disease burden on rural New Zealanders. A sheep
and beef farmer and a deer farmer, both with renal and hepatic failure were recently admitted
to the intensive care unit at Waikato Hospital (Dr. Chris Mansell; clinical microbiologist Waikato
District Health Board; personal communication April 2012). In September 2010 there was a
cluster of three cases of leptospirosis in staff at a lower north island dairy farm. Two staff were
hospitalised. An annual vaccination programme had been carried out on the dairy farm since
2003; however the Department of Labour investigation identified deficiencies in the programme
(Department of Labour, 2011).
Seventy cases of leptospirosis were notified in 2011 of which 38 of 66 (58%) were hospitalised
(ESR, 2012). Leptospira species and serovars (sv) were recorded for 57 of these, the most
commonly identified serovar was L. borgpetersenii sv Ballum (35%, 20 cases), followed by L.
borgpetersenii sv Hardjo (26%, 15 cases) and L.interrogans sv Pomona (22%, 13 cases). In 2010
sv Ballum emerged as the most frequently notified serovar in human cases. Since 2007, this rise
in Ballum cases is coincident with an increase in the proportion of farmers represented among
notified cases (Figure 2.1). In 2011 36 of the 62 cases with occupation recorded were identified
as farmers or farm workers, with 10 of the 62 working in the meat industry.
Figure 2.1: Proportion of notified leptospirosis cases infected with serovar Ballum (solid line) and
associated with farming occupation as a function of time. Data sourced from ESR annual
surveillance reports and Thornley et al (2002).
An observational pilot study of urinary shedding in dairy herds with a history of regular
vaccination was carried out in 2010/2011 (Parramore et al., 2011). There was evidence of
leptospiral shedding in 30% of the herds and in 13% of animals from positive herds. Age at first
vaccination was the only significant factor associated with the probability of shedding at the
herd level. The results suggest that leptospiral challenge of calves at an early age and potential
human exposure still exists on dairy farms using vaccines. Vaccinating already infected animals
may not be fully effective, as it appears that vaccination after natural challenge reduces vaccine
efficacy (Hancock et al., 1984). Neither vaccine type nor the number of serovars included (2 vs
3) altered the shedding probability. However it is important to note that no serological data
were available from the sampled animals, information about vaccination timing from farmers
appeared somewhat uncertain, and tests employed may not be 100% accurate. Therefore, the
results are preliminary and require further confirmatory work.
7
Motivated by the above information, the New Zealand Veterinary Association (NZVA)
commissioned this systematic review of leptospirosis vaccination. The review aims to determine
“best practice” protocols for ruminant vaccination for leptospirosis with the primary goal of
vaccination being the protection of humans. There are multiple other benefits from ruminant
vaccination such as reduction of clinical disease and sub-clinical health and production effects.
While these are not the primary focus of this work, it is likely that they would be benefit from a
best practice vaccination regardless.
This introductory section presents the situation today and a recent history of human infection
with leptospirosis in New Zealand, human leptospirosis in an international context and
concludes with detailing the search methodology for subsequent review.
2.2 The international human leptospirosis context
Globally leptospirosis is an important zoonotic disease with three main epidemiological patterns
(1) flooding associated; (2) poverty associated and (3) occupational exposure (Vijayachari et al.,
2008). The source of infection in humans is direct or indirect contact with the urine of an
infected animal, and globally these are diverse species including livestock, wildlife or vermin
(Plank and Dean, 2000). For this reason the disease may be prevalent in both urban and rural
settings and depends on animal contact and environmental and socio-economic conditions that
facilitate transmission. Leptospirosis is a protean disease and commences as an acute,
generalized illness that may be mistaken for influenza in humans. However, the disease can
progress to severe sequellae such as acute renal failure, pulmonary haemorrhage and cardiac
complications (Levett, 2001). Annual incidence is estimated from 10 to 100 cases per 100,000 in
warm tropical regions with estimates of one tenth of that for temperate climates. However
worldwide there is likely underestimation of the burden of leptospirosis (Victoriano et al., 2009).
A WHO project is currently estimating the global impact of Leptospirosis in people.
A 2009 review of leptospirosis in the Asia Pacific region characterized countries into either high
(>10 case per 100,000 per year), moderate (1 to 10) or low incidence (<1) (Victoriano et al.,
2009). India was identified as a high incidence country with carrier animals including rats, pigs,
cattle, bandicoots and dogs. Hong Kong SAR reports low incidence with fewer than seven local
cases a year over the period 2001 to 2006 . Victoriano and co-authors acknowledge that
surveillance and data collection systems differ between countries preventing an accurate
estimate and comparison of the true burden of disease between countries. Key prevention and
control interventions recommended included rodent control, domestic animal vaccination and
social control measures such as awareness and health promotion.
A review of leptospirosis in Australia reports an annual incidence of 2.1 cases per 100,000 in
Queensland and identifies the two occupational groups at most risk as workers in banana
plantations and on dairy farms (Tulsiani et al., 2010). However over the past decade there has
been a shift in risk from occupational to recreational. In 2008 international travel and/or
recreation accounted for approximately 35% of cases reported to the enhanced surveillance
system at the WHO Collaborating Centre for Reference and Research on Leptospirosis in
Brisbane (Lau et al., 2010a).
Recent work in American Samoa reported antibodies in 15.5% of 807 participants,
predominantly against three serovars that were not previously known to occur in American
Samoa (Lau et al., 2012b). Having piggeries around the home and living at lower altitudes were
statistically significant risk factors for sero-positivity (Lau et al., 2012a).
8
2.3 Human leptospirosis in New Zealand
The epidemiology of leptospirosis in New Zealand is unique with our ruminant livestock species
being key maintenance hosts (Ayanegui-Alcerreca et al., 2007; Heuer et al., 2007a; Dorjee et al.,
2008). From the 1980s to the present there has been widespread uptake of vaccination of dairy
cattle and pigs. This has been associated with a reduction in human cases from the peak of 875
in 1974 to approximately 100 cases over the period 1997 to 2000 (Thornley et al., 2002), a level
at which case numbers remained up to 2011 (Figure 2.2). This incidence risk of 2.5 per 100,000
places New Zealand in the moderate incidence category for the Asia Pacific region (Victoriano et
al., 2009) and globally (Tulsiani et al., 2010). Despite a large reduction in case numbers
leptospirosis continues to be a severe disease for rural New Zealanders with 50% of notified
cases hospitalized (Thornley et al., 2002; ESR, 2012).
Figure 2.1: Leptospirosis notifications and laboratory reported cases by year 1997- 2011.
Source: ESR Notifiable and other diseases in New Zealand 2011.
A review of leptospirosis notification data from 1990 to 1998 identified the emergence of
serovar Ballum as an important cause of human disease (Thornley et al., 2002). This trend
continued and was reported in an updated report covering the period 1999 to 2008 (Paine et al.,
2010). As reported above, Ballum has recently emerged as the most frequently notified serovar
in human cases. Prior to this time most human cases were due to Hardjobovis or Pomona
(Thornley et al., 2002; Paine et al., 2010). The maintenance hosts for Ballum in New Zealand
include the rat, mouse and hedgehog (Marshall and Manktelow, 2002). Given the recent
increase in the proportion of farmers represented among notified cases (Figure 2.1) there may
be a link with rodents foraging and thereby contaminating concentrate rations for livestock
(especially dairy cattle), or it may be that the livestock are the source of Ballum for human
cases. Such questions around the emergence of Ballum are not the focus of this review but
warrant mention here as areas for important future work, potentially with regard to inclusion of
this serovar in animal vaccines.
New Zealand’s Department of Labour recognizes leptospirosis as an occupational disease. Under
the Health and Safety in Employment Act (1992) a case of leptospirosis is regarded as “serious
harm” and the risk of being infected is a “significant hazard” (Occupational safety and health
service, 2001). Work in human leptospirosis over the last five years at Massey University has
predominately focussed on meat industry employees. Measuring serology and kidney culture
9
rates in one sheep abattoir revealed the extent of real exposure in workers: during a typical
factory day, one slaughter worker was exposed to an estimated 3-18 carcasses contaminated
with live Leptospira in kidneys (Dorjee et al., 2011). Once the rate of exposure was known, the
next question was how effective exposure transmitted to infection, i.e. how many workers
actually got infected with Leptospira. This was measured subsequently in 8 abattoirs by
sampling workers twice at an interval of one year, and calculating rates of sero-conversion as a
measure of infection. This resulted in annual infection rates among abattoir workers processing
sheep of 12.3% (n=384). The rate was lower in workers processing cattle (1.5%; n=158) or deer
(0%; n=50). The highest sero-prevalence, however, was found in deer plant workers (13-18%),
followed by plants processing sheep (6-14%) and cattle (3-4%) (Dreyfus, 2012). The high
prevalence and low incidence of new infections in deer plants is indicative of a more or less
permanent sero-positive state due to past clinical episodes followed by long seropositive
periods and/or frequent re-exposure without subsequent illness.
In meat-workers, sero-incidence data coupled with data on time off work due to “flu-like” illness
assisted in quantifying the burden of disease. In sheep plants, clinical illness associated with flulike symptoms was twice as frequent in workers who sero-converted to Pomona or Hardjo, i.e.
were infected between two sampling points one year apart (Figure 2): 47% of infected vs. 24%
of non-infected workers were affected by flu-like symptoms and an average of 4 days absence
from work. This translates to a 1 in 36 chance of illness due to leptospirosis in 12 months for
every worker regardless of work position. Once worker-position was taken into account, having
a work position on the slaughter board accounted for a 4-8 fold higher risk being highest at the
front i.e. sticking area (8x) and decreasing towards the dressed carcass processing end (Dreyfus,
2012).
384 workers / 1 year
47 (12%) got infected
22 (47%) got flu-like illness ( 4 days away from work)
25 did not get flu-like illness
337 did not get infected
82 (24%) got flu-like illness ( 4 days away from work)
255 did not get flu-like illness
Figure 2.3: Path-diagram of the rate of new infections with Pomona or Hardjo in workers of
sheep processing plants, and the risk of clinical illness in 2009/10. This related to a total risk
of contracting clinical leptospirosis of 1:36 workers (2.7%) within one year.
Little information is available as yet about comparable risks for farmers, vets and other people
with frequent animal contacts in the livestock industries. It is the intention to collect such data
in the near future. A survey of more than 300 veterinary students established a baseline
prevalence for Hardjobovis, Pomona and Ballum in 2011, all students testing negative (Fang,
personal communication).
10
3. Hosts – pathogen relationships in NZ
3.1 Host species and Leptospira serovars in NZ
The history and distribution of mammal host species and Leptospira serovars in New Zealand
were reviewed by Marshall and Manktelow (2002). This and further contributions to this topic
are summarised in Table 1. Since genotypes of Leptospira can generally not be associated with
unique bacteria species, this overview classifies the pathogen types only by serovar name.
The first isolation of Pomona in New Zealand was from a clinically affected calf at Wallaceville
Animal Research Station, 1950, followed by large scale testing of over 13,000 bovine sera at
Wallaceville 1952-55 (McDonald and Rudge, 1957). Tarassovi and Pomona were found in pigs in
1958. Tarassovi was subsequently also isolated from deer, goats and horses. It was then almost
20 years until a series of serological studies and pathogen isolations began in 1975 (Ryan and
Marshall, 1976).
Host types: Maintenance and accidental (opportunistic or spill-over) hosts are differentiated.
The concept assumes that Leptospira serovars have lower pathogenicity for maintenance than
for accidental hosts while being equally or similarly infectious. The consequence is that
maintenance hosts remain infected and a host-pathogen equilibrium is established by a
continued re-/infection cycle balanced by a marginal immune response with partial but
incomplete pathogen elimination. That equilibrium can get out of balance, for example when
environmental conditions favour the pathogen, causing outbreaks in maintenance hosts, or by
adverse conditions, causing pathogen extinction or the establishment of an equilibrium at a
lower endemic level (i.e. lower prevalence).
Climatic conditions in New Zealand favour the establishment of equilibria for several Leptospira
serovars and hosts.
Table 3.1: Data from published studies showing animal and herd prevalence by year, species and age of
livestock in New Zealand
Year
Herds
Hard
Pom
H/P
Animals
Hard
Pom
H/P
REF
Beef heifers 12-18 m old
2006
95
62%
26%
69%
1,265
34%
12%
39%
2
Mixed age beef cows
2009
116
92%
72%
97%
2,308
50%
25%
58%
1
Mixed age beef cows
2010
21
86%
67%
95%
338
45%
19%
55%
3
Dairy cows
2011
44
30%*
445
Slaughter age lambs
2004
21
86%
29%
91%
619
16%
4%
19%
4
Slaughter age lambs
2005
74
27%
7%
31%
2,139
1.7%
0.5%
2%
4
Mixed age ewes
2009
161
91%
74%
97%
3,361
43%
14%
51%
1
2004
110
68%
20%
74%
2,016
61%
8%
64%
5
Mixed age deer
2009
98
60%
49%
76%
1,992
26%
10%
34%
*Urine shedding (darkfield microscopy/PCR, 10 cows per herd); **Deer from non-vaccinated herds; L.
interrogans sv Hardjo, Pom L. borgpetersenii sv. Pomona, H/P Hardjo or Pomona; key for references
[1=Dreyfus, 2012; 2=Heuer, 2007; 3=Sanhueza, 2012; 4=Dorjee et al., 2008; 5=Ayanegui-Alcerreca et al.,
2007]
1
CATTLE
4%*
SHEEP
DEER
9-30m old deer**
11
Trends:
Humans – Hardjo accounted for 2/3 of human notified cases in NZ in 1975 (Ris, 1975) whereas
Ballum started to rank highest in 2009 (ESR, 2011). Until 2005, the majority of notified cases
were meat workers followed by farmers. However, farmers have been ranked highest among
notified cases since 2006, followed by meat workers and other groups in contact with animals.
Assuming that MAT titres after a clinical episode last for up to 10 years (Blackmore et al., 1979),
the infection incidence of meat workers was believed to be around 0.5% during the 1980s when
there was still a very high infection prevalence in the dairy cattle population (Blackmore and
Schollum, 1982). However, recent sero-conversion data of abattoir workers processing sheep,
deer and cattle revealed a 12.3% incidence (Dreyfus, 2012). The new infection rates were
highest at sheep processing plants, followed by deer and cattle plants. Workers at sheep plants
had a 12.2% risk of becoming infected with Hardjo (3.6%) or Pomona (9.4%) in the course of a
single slaughter season (12 months). The data also showed for the first time in New Zealand,
that 1 in 36 workers experienced clinical illness due to an infection with either of these serovars.
Illness caused an average of 4.4 days being away from work. The data suggest that ESRnotification rates of leptospirosis may be underreported by a factor of 40-50 times for abattoir
workers (see also section 2.3, page 8).
Conclusion: New data about the incidence of illness associated with leptospirosis among highly
exposed workers at the slaughter board of abattoirs imply an imminent need for similar studies
among farmers, veterinarians and other people in contact with farm animals.
Table 3.2. Host-pathogen associations of Leptospira serovars in New Zealand (serovars in parenthesis
are sporadic observations)
Host
Leptospira servovars
Reference
Human
Ballum, Hardjobovis, Pomona, (Tarassovi, ESR 2001-09
Canicola, Copenhageni, Australis)
Farm animal species:
Dairy cattle
Beef cattle
Sheep
Deer
Hardjobovis, Pomona, (Copenhageni, Ballum)
Hardjobovis, Pomona, (Copenhageni, Ballum)
Hardjobovis, Pomona, (Copenhageni, Ballum)
Hardjobovis, Pomona (Copenhageni, Ballum,
Arborea* )
(Hathaway, 1981)
(Hathaway, 1981)
(Hathaway, 1981)
(Asher, 1986; Wilson et al., 1998;
Subharat et al., 2011b)
Fallow Deer
Pomona, Hardjobovis
(Marshall and Manktelow, 2002)
(Hilbink and Penrose, 1990)
Pig
Horse
Pomona, Tarassovi
Hardjobovis, Bratislava, (Ballum, Copenhageni,
Tarassovi, Pomona, Canicola)
Copenhageni, Hardjobovis, Pomona, (Ballum,
Tarassovi, Canicola)
Dog
(Hilbink F, 1992; O'Keefe et al.,
2002)
Wild animal species:
Rat
Ballum, Copenhageni
Mouse
Ballum
(Marshall and Manktelow, 2002)
Deer
?
(Hathaway, 1981)
Rabbit
?
Possum
Balcanica
Hedgehog
Ballum, (Pomona)
(Marshall and Manktelow, 2002)
Pig
?
(Marshall and Manktelow, 2002)
* A number of other serovars were identified in a study testing a panel of 22 serovars. However, with
Medanensis, Szwajizak, Tarassovi, Grippotyphosa, Celledoni, Australis, Zanoni, Robinsoni, Canicola,
12
Kremastos, Bulgarica, Cynopteri, Bataviae, Djasiman, Javanica, Panama, Shermani, and Topaz were likely
explained by known cross-reactivity with endemic serovars (Subharat et al., 2011b).
Sheep – A 1975 study reported 65% animal prevalence and titres over 1:1000 to Hardjobovis in
10 flocks of sheep using the MAT (Ris, 1975). A letter to the editor of NZVJ in 1980 announced
the first known successful culture of Hardjobovis in sheep (Bahaman et al., 1980). Pomona was
rarely seen in sheep, associated with sporadic clinical disease. Only recently has it been
suggested that sheep may be a maintenance host for Hardjobovis while Pomona was not
considered as such. In contrast, a recent and yet unpublished NZ-wide survey (Dreyfus, 2012)
from 161 flocks demonstrated that 97% of the flocks had at least 1/20 sero-positive (titre ≥1:48)
adult ewes (91% Hardjo, 74% Pomona) and 51% ewes infected (43% Hardjobovis, 14% Pomona).
An abattoir survey in 2005/06 isolated Leptospira from 22% kidneys of Hardjobovis- and 17% of
Pomona-seropositive carcasses of lambs or hoggets (Dorjee et al., 2008). Only 1/162 (0.6%)
flocks were vaccinated (Dreyfus, 2012).
Conclusion: Hardjo is highly prevalent in sheep breeding flocks and this species probably
constitutes a reservoir host. Pomona is also endemic and sheep possibly are a reservoir host.
Dairy Cattle – until recently, the prevalence of Leptospira in dairy cattle was assumed to be low
due to vaccination, which was believed anectdotally to have been adopted by more than 90% of
dairy farmers for at least 10 years. However, a pilot study of 44 dairy herds (Parramore et al,
unpublished) found 30% herds and 4% of 445 cows to be shedding Leptospira in urine based on
samples from 10 cows per herd tested by PCR and dark-field microscopy. The probability of
having a shedder in the herd was low on farms where calves were reported to have been
vaccinated for the first time below the age of 6 months, and almost zero when vaccinated up to
3 months of age (Parramore et al., 2011).
Conclusion: despite extensive use of vaccination, continued shedding is apparent, especially on
farms where vaccination may be applied inconsistently or too late. Given its implications, this
preliminary finding calls for immediate verification.
Beef Cattle – beef herds had not been sampled prior to 2005. In 2006, replacement heifer mobs
12-18 months of age of 69% herds (n=95) and 39% of the replacement heifers (n=1,265) were
sero-positive to either Hardjo (34%) or Pomona (12%) (Heuer et al., 2007a). Two subsequent
population based studies found 95-97% beef breeding herds and 55-58% of the mixed age cows
positive to Hardjo (45-50%) or Pomona (19-25%). A survey in 2009 involved 116 herd and 2,308
cows (Dreyfus, 2012). The 2010 study estimated fetal loss due to leptospirosis selected aborting
and non-aborting cows in 21 herds and 338 cows (Sanhueza, 2012). Both investigations tested
20 mixed age cows. In the 2009 survey, farmers of 19/116 (16%) beef breeding herds reported
that their beef stock had been vaccinated (Dreyfus, 2012). In the 2006 survey of replacement
heifers, 9/94 (10%) beef breeding herds were vaccinated (Heuer 2007), whereas 21/45 (47%)
herds reported vaccinating in the study of fetal loss (Sanhueza, 2012). Voluntary vaccination of
beef herds appeared to depend on the quality of farm management as the latter study involved
farmers who were monitoring fetal loss, consented to the study protocol and were able to
identify cows that had aborted and present them for sampling.
Conclusion: the sero-prevalence of Hardjo and Pomona, and possibly other serovars, remains as
high among beef cattle as in sheep breeding flocks.
Deer – Leptospirosis in farmed deer in New Zealand was extensively reviewed recently
(Ayanegui-Alcerreca et al 2007). Clinical letospirosis was first diagnosed in farmed deer in 1981.
Serovar Pomona was isolated from outbreak herds in the early 1980’s and this remains the only
serovar implicated with clinical disease in deer. Culture and serological evidence for Hardjobovis
was also described in early reports. Limited surveys carried out in the mid and late 1980’s
indicated that leptospirosis was prevalent, with Hardjobovis being the predominant serovar.
13
Those surveys, together with a clinical occurrence, confirmed that Copenhageni also infected
and clinically affected deer. A larger Southern North Island survey in the early 1990’s (Wilson et
al 1998) demonstrated a 73.6% animal seroprevalence to hardjobovis, 41.5% to Pomona, 11.3%
to Copenhageni and 15% tarassovi. The significance of the latter, along with low titres for
Australis, Bratislava and Balum in various studies remains unknown. More recently, Subharat et
al (2011b) reported serological evidence for serovar Arborea on two farms from screening of a
serum bank for 23 (16 exotic) potential serovars. However, attempts to isolate the organism
were unsuccessful. A national serosurvey in 2005-6 (Ayamegui-Alcerecca et al 2010) observed
81% of 110 herds positive, comprising 78% Hardjobobis and 16% Pomona, with some dual
serovar infections. The individual animal seroprevalence was 61%, 6.6% and 1.2% for
Hardjobovis, Pomona and Copenhageni, respectively. There were no regional differences. A
2009 serosurvey of 99 farms (Dreyfus et al, unpublished) yielded siminar herd seroprevalence
data (76%), and 34% animal seroprevalence. While there is reasonable awareness of
leptospiroisis among deer farmers, vaccination is practised by approximately 10%. Conclusion:
Leptospirosis is widespread in the farmed deer population, with herd and individual animal
prevalence similar to that seen in sheep and beef cattle. Deer are a reservoir host for
Hardjobovis and likely a reservoir population for pomona.
Dogs – a prevalence of 0.9% was observed for Copenhageni and 0.7% for Ballum at a MATcutoff of 1:100 in a cross-sectional study of 8,730 rural and urban dogs involved in a 1990-91
New Zealand Hydatids Council serological survey (Hilbink F, 1992). The prevalence of
Copenhageni was almost seven times higher in dogs presented as cases to 45 small animal
veterinary clinics in Auckland (6%; 31/561). The prevalence of Copenhageni was lower in the
South Island (0.1%; n=3,671) than in the North Island (1.3%; n=6,029). A lower North Island
survey 10 years later showed 9.5% being sero-positive for Copenhageni in 433 rural and urban
dogs with similar prevalence in both environments. However, Hardjo was almost exclusively
found in rural dogs (15/315; 4.8%), only 1/146 (0.7%) urban dogs were sero-positive for Hardjo
(O'Keefe et al., 2002). The total sero-prevalence in dogs for serovars Hardjo, Pomona,
Copenhageni Grippotyphosa, or Canicola was 14.2% (66/466).
Conclusion: Serovar Copenhageni is likely the dominant serovar in dogs throughout New
Zealand. Hardjo may be transmitted from sheep and beef cattle to farm dogs, a possible source
of exposure to these two serovars for humans.
3.2 Transmission routes
A model for the transmission between species and persistence of Leptospira in reservoir hosts
and the environment is presented in Figure 1. In the model, reservoir hosts for Hardjobovis and
Pomona are beef cattle, sheep and deer while farm dogs, rodents and wild living animals are
accidental hosts contributing to environmental contamination. Direct contact with shedding live
and dead reservoir hosts, indirect contact with contaminated environment (e.g. floods on
pasture, ponds, drains, rivers) causes infection in humans. Environmental contamination is
augmented by favourable weather conditions (high rainfall, moderate to high temperature), an
assumption supported by observation of outbreaks of leptospirosis during or after major floods
(Dorjee et al., 2005).
Leptospira preferentially colonise kidney tissues, surviving for up to 13 weeks, and are excreted
in urine. Entry ports for human infection are abrasive skin areas, mucosa of eye, nose and
mouth, and possibly softened skin of meat workers wearing rubber gloves and plastic sleeves
for extended period of times during work (Dreyfus, 2012).
14
Reservoir hosts(?)
Feral animals
Mouse, Rat
Possum
Hedgehog
Rabbit
Deer
Goat
Pig
Beef cattle
Sheep
Deer
Dairy cattle
Dog, pig
Vectors
Environment
Water logged pasture
Ponds
Drains
Rivers
[Rain, temperature]
[Co-factors]
People
[occupation, behaviour]
Figure 3.1: Ecological model of leptospirosis in New Zealand
3.3 Conclusions: host/pathogen relationships
Possibly driven by widely adopted vaccination of dairy herds, a gradual spatial replacement of
sheep, beef, deer herds by dairy herds, a long term slow drift in weather conditions towards
higher temperatures and more rainfall, the enforcement of protective measures at slaughter
and meat processing plants, the epidemiology of leptospirosis appears different today
compared to the pre-2000 era of intensive leptospirosis research. Today, the primary source for
human infection at abattoirs appears to be sheep followed by deer and, to only a small extent,
cattle. Based on high sero-prevalence and high kidney culture isolation rates to both Hardjo and
Pomona, sheep are likely to be maintenance hosts for these serovars. Since previous ecological
considerations did not consider sheep as a maintenance host or major source for human
infection (Hathaway, 1981), the epidemiological importance of sheep, and possibly of other
hosts and other serovars, appears to have undergone a significant change.
4. Environmental effects
4.1 Introduction
Globally, leptospirosis is a recognised re-emerging bacterial disease (Levett, 2001; Bharti et al.,
2003; Cruz et al., 2009; Ko et al., 2009) and this re-emergence is likely influenced by
environmental conditions including climate and urbanisation (Dufour et al., 2008; McMichael et
al., 2009; Paine et al., 2010). The three main epidemiological patterns of human leptospirosis
(flooding, poverty and occupation) clearly reflect the importance of environmental drivers in the
transmission of this disease (Figure 4.1). Although not as well documented in animal disease or
15
infection, the environment plays a dominant part in the epidemiological triangle that
contributes to leptospirosis in New Zealand livestock species.
This section presents a brief overview of evidence for the role of the environment in
leptospirosis in New Zealand, with evidence from both human and animal data. We limit our
discussion in animals to two environmental drivers: climate and farming practice. With regard to
this review it is important to be aware that the effect of the environment on leptospirosis must
be seen in conjunction with the effect of the environment on the ability an animal has to create
an effective response to vaccination. Environmental effects that are important with regard to
response to vaccination include nutrition, housing, shelter and other “stressors”.
Leptospira are shed into the environment by infected animals and they may survive for days to
months in freshwater, soil, or mud. Their survival is enhanced by humid environments and
higher temperatures (Levett, 2001). High rainfall periods combined with warm weather are
recognized as risk factors for leptospirosis transmission in many diverse parts of the world
including Mexico (Leal-Castellanos et al., 2003), Germany (Desai et al., 2009), Brazil (Cruz et al.,
2009) and India (Vijayachari et al., 2008).
In the Pacific Islands, increases in leptospirosis cases frequently follow heavy rainfalls when
flooding occurs and rats search for higher ground. In late April 2012 there were seven confirmed
fatalities from leptospirosis with 13 other deaths, suspected in Fiji. The cases followed massive
flooding in January 2012 (ProMED Ahead Digest-mail).
16
Figure 4.2: Leptospires are maintained in nature by mammalian reservoir hosts. Humans acquire
leptospirosis through direct contact with infected animals or by indirect contact with an environment that
has been contaminated by animal urine. The cycle of transmission is in turn driven by environmental forces
including socio-demographic factors, climate and land use. Figure reproduced with permission from (Lau et
al., 2010b)
4.2 The New Zealand environment and Leptospirosis
New Zealand is no stranger to anthropogenic environmental change, transforming from
indigenous forest to predominantly pastoral farming over a short time. Furthermore, our
farming sector is rapidly adaptive to market forces, and changes in land-use and farming
practices have environmental effects. The introduction of deer farming, for example, has
brought previously feral species into direct contact with more traditional livestock species
(Heuer et al., 2007b; Hilson, 2007), a process enabling transmission of pathogens to additional
host species (Woolhouse and Gowtage-Sequeria, 2005). Within New Zealand there is evidence
of the presence of specific leptospiral serovars Arborea in deer (Subharat et al., 2010) and
Ballum in humans (Thornley et al., 2002; ESR, 2012). There is also evidence that clinical disease
in sheep and deer is increasing, with higher morbidity and mortality in lambs and young deer
(Dorjee et al., 2005; Ayanegui-Alcerreca et al., 2007). This may be associated with
environmental change such as co-grazing (Subharat et al., 2008) and/or increased rainfall.
17
4.3 Climate
An abattoir study conducted by Dorjee et al in the southern north island reported significantly
higher sero-prevalences to Hardjo-bovis in lambs sampled in May and June 2004 than from
those sampled in the corresponding months in 2005 (Dorjee et al., 2008). This between-year
effect was postulated to have been due to high rainfall accompanied by widespread surface
flooding in February 2004 and relatively less rainfall in 2005. Other reports of an association
between rainfall and surface flooding and outbreaks of leptospirosis in lambs have previously
been reported in New Zealand (Vermunt et al., 1994; Dorjee et al., 2005).
Fang Fang (2012) conducted an abattoir study in the Waikato region and sampled urine, kidney
and blood from 399 lambs and 146 beef from six suppliers . The reported animal-level seroprevalences found in sheep (57%) and cattle (73%) were higher than previous studies had
reported (Heuer et al., 2007a; Dorjee et al., 2008) and a 27% shedding rate was detected by
both urine and kidney PCR. Sero-positivity was defined at a MAT titre dilution of 1:48 or more.
The shedding rate (as determined by positive urine PCR) in sero-positive sheep was 54.1%,
whilst that in sero-negative sheep was 2.8%. The shedding rate (as determined by positive urine
PCR) in sero-positive cattle was 28.2%, whilst that in sero-negative cattle was 3.0%. A sustained
period of heavy rain coupled with warm weather had occurred in the six weeks prior to
sampling.
The above studies provide anecdotal evidence as to the effect of climate on leptospirosis in New
Zealand. It is reasonable to suggest that data that exhibit a seasonal pattern are likely to be
associated with climate and for this report we exam seasonality within available leptospirosis
data. However, it is important to remember that there are drivers other than climate that may
produce seasonality in disease data, for example farm production and animal breeding cycles.
As leptospirosis in animals is not notifiable we have accessed laboratory submission data for
serovars Hardjo and Pomona provided by Gribbles animal health to explore seasonality. It is
important to be aware that infections from Hardjo and Pomona present differently as Hardjo is
considered to be in a maintenance host relationship with cattle in New Zealand, and therefore,
the disease caused by this serovar behaves differently to that of a Pomona infection. Ruminants
are considered accidental hosts for Pomona and thus this serovar generally causes more severe
disease than Hardjo. For the laboratory submission data a positive result was defined as a MAT
titre of 1:50 dilution or greater. Figure 4.3 shows a monthly box plot of the proportion of
laboratory submissions from cattle positive to L. Pomona and L. Hardjo over the period 2003 to
2010 inclusive. Data sourced in this way has some limitations: it likely reflects the most severe
cases and those able to pay for veterinary visits and sample analysis. Nevertheless two patterns
emerge. The Hardjo data shows that approximately 50% of samples submitted were positive
and there is no seasonal pattern. The Pomona data shows a seasonal pattern with the highest
proportion of positive submissions occurring in the winter and spring months. This peak of
submissions from cattle in June – September is likely attributable to higher rainfall and
therefore longer periods of with elevated soil moisture in winter, allowing leptospira to survive
for up to 7 weeks (Hellstrom and Marshall, 1978) while maintaining virulence. Another
contributing factor to this pattern is seasonal calving subsequent to this peak period which
would suggest a relationship of clinical submissions to abortion. However, the sero-prevalence
trend for Hardjo was non-seasonal and Hardjo was reported to have a similar impact on fetal
loss in beef cattle as did Pomona (Sanhueza, 2012).
18
Two recent analyses of human leptospirosis notification data (1997 to 2008) did not find a
seasonal pattern (Paine et al., 2010; Meade, 2012), contrary to the pattern suggested by Figure
4.3.
Figure 4.3: Monthly box plots of the proportion of laboratory submissions from cattle positive for L.Hardjo (above)
and Pomona (below) over the period 2003 to 2010. The horizontal blue line represents the median proportion.
Data sourced from Gribbles animal health laboratories.
4.4 Mixed-species grazing management
Advantages of mixed-species farming (deer, sheep and/or cattle) include pasture management
and internal parasite control (Hilson, 2007). However, mixing of host species can result in
pathogen transmission and infection across species. A longitudinal serological survey occurred
on 20 mixed species (sheep and/or beef cattle) deer farms in the lower north island from 2006
until 2008 (Subharat, 2010). Deer herds were more likely to be Hardjo positive on farms with
19
hilly topography (PR1=4.67, p<0.001) and when deer were co-grazing with Hardjo positive cattle
herds (PR=1.93, p=0.022) or sheep flocks (PR=1.70, p=0.007). Deer herds were more likely to be
Pomona positive when deer were co-grazing with Pomona positive cattle herds (PR=7.50,
p=0.050).
These results suggest that inter-species transmission of leptospires may be occurring on farms.
However as there may be host-adaption within serovars molecular studies are need to confirm
this. Molecular studies based on the multi-locus sequence typing scheme of Ahmed (Ahmed et
al., 2006) are occurring at Massey on isolates gathered from serovars isolated from cattle and
sheep on the same farm as part of the abattoir study described above (Fang, 2012).
5. Farm management
New Zealand’s main pastoral farming enterprises (dairy, beef/sheep and deer) have a seasonal
production linked to feed availability and animal reproduction cycles. Within the context of best
practice for vaccination, farm production cycles present opportunities for both leptospirosis
vaccination and for transmission of infection. For example in the seasonal calving dairy herd
culling decisions based on production are usually made at drying-off in May. At that time whole
herd dry-cow mastitis therapy may be used and that is seen by farmers as an opportune time to
booster-vaccinate adult dairy cattle.
This section will give an overview of the production cycle for each farming enterprise identifying
opportunities for both infection and vaccination. It also identifies the risk activities for humans
associated with each enterprise. Interviews with Dr. Jenny Weston, Prof. Paul Kenyon and Prof.
Steve Morris from the Institute of Veterinary, Animal and Biomedical Sciences, Massey
University informed these sections. It is important to be aware that these production cycles
attempt to represent what occurs only on the majority of farms, they cannot reflect the
variation that occurs from farm to farm.
5.1 Seasonal calving dairy herd management
Figure 5.1 shows a timeline of farm management events that representative of a New Zealand
spring calving herd. Calving starts in mid to late July and ends by early October. Calves rely on
colostrum for maternal transfer of antibodies. It is generally recognized that 50% of calves do
not receive adequate colostrum (Vermunt et al., 1995; Wesselink et al., 1999). Calves are
removed from the cows daily, very few farmers will pick up calves twice daily, and this can mean
that calves may be up to 23 hours with their dams in the paddocks. Approximately 50% of dairy
farmers will stomach tube calves with colostrum, the rest relying on calves suckling or receiving
colostrum through calf feeders.
Generally the early and late calves are of lower breeding value as they are the result of bull
matings, so these are culled as bobby calves for slaughter or are sold for calf rearing. Female
calves from artificial breeding (AB) are kept as replacements. These are almost exclusively
1
Prevalence ratio
20
reared on the home farm until weaning at 8 to 10 weeks of age. Early animal husbandry includes
disbudding by vets or vet techs at 3 to 6 weeks. This is an opportunity to start the vaccination
programme, for example the Massey vet clinic gives a 7-in-1 vaccination (clostridial 5-in-1 plus
leptospirosis Hardjo and Pomona).
Mating occurs from October to December. The heifers are almost exclusively put to bulls while
the milking herd usually runs two cycles of artificial breeding and are then followed up with
bulls.
Within the New Zealand dairy enterprise it is increasingly common practice to raise the young
stock off the milking platform. The contract rearing of calves and heifers post-weaning presents
an opportunity for them to mingle with other dairy stock and other species from the rearer’s
farm thus potentially exposing them to infection. Furthermore, the fact that this young stock is
grazed away may mean that vaccination may be delayed. The most common practice is that
young stock leaves the home farm on June 1 as rising one year olds. At the same time there is
the return of pregnant rising two-year old heifers to the home farm. However, some farmers
send the calves away from the home farm in December as four-month-olds. Commercial grazers
may be used or young stock may go to a run-off owned and managed by the herd owner.
Figure 5.1: Timeline of farm management events in a representative New Zealand spring calving dairy herd
5.2 Issues around vaccination in seasonal calving dairy herds
High rainfall periods are a risk factor for leptospirosis transmission (Hartskeerl et al., 2011) and
booster vaccinating adult stock before these periods is sensible. Historically veterinarians
vaccinated the milking herd at the time of manual pregnancy testing (March/April) and this
fitted in with the traditional risky autumn period for transmission. However, the adoption of
scanning technology has brought the time of testing forward with most herds scanning in
Jan/Feb. This appears to be rather early for the annual booster to have an impact on maternal
antibodies in colostrum if that were intended. The annual pre-calving booster is therefore best
be applied at dry-off around May to allow for antibody in colostrum, or after calving to prevent
MDA interference with early vaccination. An in-house study by Virbac Animal Health evaluated
21
MAT antibody levels in newborn calves when dams were vaccinated 54-90 days prior to calving.
The author suggested that dams should be vaccinated at least 70 days prior to calving for
optimal calf immunity (Pulford, 2006). However, none of the dams in this study was vaccinated
as early as 180 days before calving as it would occur if cows were booster-vaccinated at
scanning in Jan/Feb.
Decisions about when to vaccinate the adult cow have been around the conflict between giving
a "colostral" vaccination (early to mid July) versus vaccinating before the wet weather risk
period ( April/May) versus the convenience of the vaccination at drying-off, which occurs end of
May. The timing of the wet weather period and drying off vary from season to season to season
and between geographical location.
The uncertainty about when to vaccinate calves has been influenced by having a number of
products on the market with conflicting advice about when best to start the vaccination
programme. The key conflict here is the balance between interference from maternal immunity
and concerns about leaving calves unprotected (section 9.3).
Generally it is the beef industry that supplies bulls to the dairy industry. Beef cattle are highly
exposed to leptospirosis and vaccination of bulls for leptospirosis is rare. Exceptions include
large commercial bull farms which are also vaccinating against other diseases such as BVD.
Seasonal calving dairy herd opportunities for human infection
Milking and teat care
Assisting with dystocia
Artificial breeding
Pregnancy testing
Herd testing
Reproductive checking
Other animal health engagement
Spreading of dairy shed effluent (truck or irrigator)
Keeping of pigs (Pomona, Tarassovi)
Rodent exposure from storage and feeding of concentrate (Ballum, Copenhageni)
Changing climatic patterns, wet/dry spring, standing water
Tb testing (albeit on a bi- or tri-annual basis)
5.2
Management of sheep flocks
Adult stock
New Zealand commercial self-replacing sheep flocks put the rams out in March for 2 or 3 cycles.
Rams are brought in over November to February and generally 20 to 30% are replaced each
year. Two-thirds of flocks breed ewes first at 18 months (two-tooths) while one third breed
ewes as hoggets. 80 to 90% of flocks scan for pregnancy at the end of June early July and
lambing starts in late August. The majority of farmers practise easy-care lambing with limited
assistance for dystocia and bearings. Figure 5.2 shows a timeline of farm management events
that are representative of a New Zealand self-replacing sheep flock.
22
Pregnant ewes are vaccinated 2 to 4 weeks prior to lambing with a clostridial 5-in-1 vaccine to
enhance colostral transfer of immunity. Vaccines (Toxoplasma and/or Campylobacter) to
prevent fetal loss are given pre-breeding. Vaccination against salmonellosis may be routine or
may be in the face of an outbreak. Ecto-parasite control (dipping) occurs in summer every 4 to 6
weeks (Jan through March).
Most farmers shear ewes once a year post-weaning (Dec-Jan). These ewes will have a crutch
and belly shear in July. Less frequently there are two shears a year: one pre lamb in June/July
(enhancing fetal survival/ encouraging shelter seeking) and the second in Dec/Jan.
Young stock
Tailing/docking (tails and testicles) occurs 4 to 6 weeks after the start of lambing when most
lambs are 3-4 weeks old, often on two batches. Lambs may receive their first clostridial
vaccination at tailing or at weaning.
Weaning generally occurs in Dec-Jan at 12 to 16 weeks (28 kilos live weight). In some farming
enterprises it may occur earlier and together with the second docking, at around 8 to 10 weeks
of age. Weaning is the more common time for the first clostridial vaccine and it is boostered 4
to 6 weeks later. This is an opportunity to vaccinate for leptospirosis as well. The first worm
drench is also given at weaning and then every 28 days (for 5 to 7 times). Lambs are first shorn
between January and Match and then again in October.
If a sheep flock is not self-replacing there are more opportunities for infection of both animals
and humans as stock are co-mingled and more animal health procedures are likely to occur, e.g.
a worm drench on arrival.
Figure 5.2: Timeline of farm management events in a representative New Zealand self-replacing commercial sheep
flock
23
Sheep flocks: opportunities for human infection:
• Shearing/crutching
• Assisting with dystocia
Home slaughter: both for human consumption and for dog tucker.
• Pregnancy scanning
• Tailing/docking
Other animal health engagement (e.g. drenching)
• Changing climatic patterns, wet/dry spring, standing water
5.3
Management of beef herds
Adult stock
Bulls are purchased in July as rising two year olds and generally stay in the herd for 4 years.
Cows calve from August to October. Cows may receive a 5-in-1 vaccination two to four weeks
pre-calving. Bulls are joined with cows and heifers from October to December for a maximum of
three cycles. Bulls are often rotated between mobs of cows. Heifers are usually mated at 26
months old but if well grown can be mated as yearlings. The breeding herd is kept in age mobs
of heifers and mixed age cows. Pregnancy diagnosis of cows and heifers occurs in March.
Steers may be sold off at the yearling sales (store cattle) in September but more usual are the
spring cattle sales of steers, heifers, and dry cows.
Tuberculosis testing is done at variable times, usually after weaning or during winter. However,
most beef herds now need to be tested bi- or tri-annually.
Young stock
Calves are ear-marked at 4-6 weeks of age (November) and male calves castrated. Calves are
weaned in March and this is when the drenching programme for weaner calves also begins.
Figure 5.3 shows a timeline of farm management events that are representative of a New
Zealand beef herd.
24
Figure 5.3 Timeline of farm management events in a representative New Zealand beef herd
Beef herds: opportunities for human infection :
•
•
•
•
•
Assisting with dystocia
Pregnancy testing
marking/castrating
Other animal health engagement
Changing climatic patterns, wet/dry spring, standing water
5.4 Management of deer herds
There is wide variation in weaning date between deer farms with some pre-rut occurring as
early as mid-February to late March. Other enterprises will wean post-rut in May-June while
others may not wean at all. Vaccination of young stock (Clostridial and lepto), if done, occurs in
late Feb to early March, regardless of the weaning date. The majority of deer farmers use
anthelmintic treatments to young deer, albeit at variable frequency, during the autumn, with
repeat treatments by some late winter and through spring. About half of deer farmers give
anthelmintic to yearling and adult deer, usually either pre-rut, or early – to mid-winter. Mating
occurs from March to May, with calving from Nov to Dec. Scanning for pregnancy is done by a
minority of farmers (May-June). Figure 5.4 shows a timeline of farm management events that
are representative of a New Zealand deer herd. Due to the large variation in weaning dates
these have not been included in the figure.
25
Figure 5.4 Timeline of farm management events in a representative New Zealand deer herd
Deer herds: opportunities for human infection :
• Weaning
• Scanning
Removal of stags after mating
• Other animal health engagement, e.g. anthelmintic, copper treatment
Velvetting
Tb-testing
Up to 70% of New Zealand deer herds practice mixed-species management with sheep and/or
beef (Hilson, 2007). So the risks to humans with deer farming enterprises need to take into
account the presence of other species when they are present.
6. Production outcomes
Significance of production effects as incentive for vaccination to protect humans: In the
absence of vaccines for humans in New Zealand, preventing human leptospirosis clearly
requires the control of infection in sheep, deer and beef cattle. As publicly funded control
programmes for leptospirosis in livestock do not exist, control is voluntary and paid for by
producers.
A 2009/10 survey showed that 1/162 (0.6%) sheep, 6/99 (6.1%) deer and 19/116 (16.4%) beef
breeding farms had their stock vaccinated against leptospirosis. Farmers implement vaccination
primarily to protect themselves, their families and farm workers. An additional motivation for
investing in vaccination might be economics. If investing in leptospirosis control would return
production gains offsetting the cost of investment, farmers would be more likely to adopt
vaccination and other means for control.
This section therefore reviews current knowledge about the livestock production response
effect to infection with Leptospira from a population and cost-benefit perspective. While it is
26
known that leptospirosis affects several organ systems and can cause clinical diseases such as
kidney or liver failure, studies were only considered in this report when designed to
demonstrate associations between Leptospira infection and sub-clinical production outcomes.
Few data are available about the incidence of clinical disease whereas most production effects
were deduced from prevalence or incidence studies about sub-clinical disease.
Clinical disease with high fatality generally occurs sporadically and at apparently low incidence,
although no robust data exist, and under-diagnosis may occur. However, outbreaks have been
reported following extreme conditions of flooding or extended periods of rainfall with 5 – 15%
lamb loss (Dorjee et al., 2005). A recent survey of 1,940 farmers responding to a questionnaire
invitation mailed to 7,998 clients of 28 veterinary practices in 7 selected regions in early 2009
revealed that 1-5% farms had observed clinical occurrences of leptospirosis in the preceding 3
years (Table 6.1). Deer farmers observed clinical disease more frequently than sheep or beef
farmers, perhaps through greater awareness in response to industry initiatives. Clinical disease
(3-year incidence 4.7%) was only observed on deer farms that also grazed sheep and the 3-year
incidence on deer/sheep farms was 12.5%, suggesting transmission from sheep to deer. More
detailed information is currently being analysed (Dreyfus, 2012).
Table 6.1: Farmer reported 3-year leptospirosis occurrences of clinical leptospirosis from a mail survey
of 1,940 respondents of 7,998 clients of veterinary practices in New Zealand, 2006-8
(Dreyfus, 2012).
Species
Clinical occurrences reported/no. farms 3 year incidence
Deer
11 / 233
4.7%
Sheep
14 / 1,193
1.2%
Beef cattle
22 / 1,061
2.1%
Hence, while clinical leptospirosis is known to cause jaundice, kidney disease and
haemoglobinuria, this clinical expression of leptospirosis is only seen sporadically in any of the
pastoral livestock species in New Zealand.
In contrast, loss due to sub-clinical disease was widely believed to be negligible or absent, and
until recently when studies in deer were undertaken, had not been the subject of research
demonstrating direct causative links in any NZ livestock species. The presence of sub-clinical
disease was based on either serological prevalence or incidence of sero-conversion. Prevalence
or case-control data can at best suggest an association with production loss. Incidence of seroconversion may allow causal inferences, especially when sero-conversion was preceeding or in a
period concurrent to the measurement of production outcomes.
In deer, an initial observational study during the growth phase of young deer using
serovonversion and/or urine shedding as markers for new infection. Comparison of growth
rates from weaning to slaughter showed an average of3.7kg lower live weight at slaughter in
those showing evidence of infection. This detrimental effect was explained by serious histopathological findings in kidney tissues of sero-positive deer (Ayanegui-Alcerreca, 2006). That
author also reported a significantly greater weaning percentage (number weaned/hinds
scanned pregnant) in vaccinated compared with non-vaccinated adult hinds in a herd with high
prevalence of dual Hardjobovis and Pomona infection (97 vs. 88%, respectively). A subsequent
incidence study of deer in New Zealand found significantly higher growth rates in vaccinated vs.
non-vaccinated weaners, up to a man of 6.4kg at 12 months in a high prevalence herd (Subharat
et al., 2012) and a mean of about 6% higher weaning rates attributable to annual vaccination of
hinds in herds with evidence for moderate-strong natural challenge (Subharat et al., 2011a).
Since pregnancies have been retained at least until the immediate pre-calving period,
vaccination apparently reduced perinatal and/or pre-weaning mortality. The growth response
27
was sufficient to provide positive financial returns on the investment of vaccination when
prevalence was approximately 20% or more. An economic response for reproductive
improvement occurred when the weaning rate increased by approximately 1.3% or more.
Return on investment in vaccination ranged from 700 – 1200% (reproduction and growth,
respectively) in high infection rate situations (Wilson et al., 2009).
No data are currently available about growth or weaning effects in beef cattle or sheep in New
Zealand. Encouraged by the results in deer however, similar NZ-studies are currently underway
in sheep flocks and beef breeding herds. Results are expected by mid-2013 (Vallee, 2012).
In beef cattle, both Leptospira sv Hardjo and Pomona were associated with an increased risk of
foetal loss in a population based case-control study in New Zealand in 2010 (Sanhueza, 2012).
Conservative estimates from the study indicated that 5% and 4% of fetal losses were
attributable to Hardjo and Pomona, respectively, and were similar to foetal loss attributable to
bovine viral diarrhoea virus or Neospora caninum. Such losses may be much higher when
susceptible cattle, e.g. returning from a distant run-off, were co-grazed with cattle, deer or
sheep where leptospirosis was highly endemic. Similar associations were reported from Spain
(Ellis et al., 1978; Atxaerandio et al., 2005). Similar studies in Canada, US and Ireland estimated
6%, 10% and 50%, respectively, of bovine abortions being associated with serovar Hardjo
(Grooms, 2006). New Zealand data published by Beef&Lamb suggested that pregnancy rates of
beef herds were not associated with the sero-prevalence of serovars Hardjo or Pomona (Heuer
et al., 2007a)2. A study in Victoria, Australia, concluded that L. interrogans sv. Hardjo was NOT
associated with abortions in dairy cattle as Leptospira could not be identified by culture in
placenta or foetuses from 195 aborting cows despite being isolated from the urine of 2 infected,
apparently non-aborting cows (Chappel et al., 1989). Successful isolation of Leptospira
(serogroup Hebdomanis) from these tissues was reported from experimentally infected and
aborting cows (Ellis and Michna, 1977). Current trials involving vaccination may help determine
whether these associations are causative (Vallee, 2012).
In addition to this, well evidenced risk of Leptospira infection on abortion, there appears to be a
sub-clinical effect on conception rates in dairy cattle. The median time from calving to
conception was 34 days longer and one more breeding was required per pregnancy in seropositive vs. sero-negative to serovar Hardjo first-calving dairy cows in a US-study. A UK study of
herds with evidence of exposure to leptospirosis suggested that vaccination against serovar
Hardjo potentially increased conception rates and reduced culling (Dhaliwal, 1996).This subclinical effect was more pronounced in spring calving cows and attributed to conception failure
and early embryonic death (Guitian et al., 1999). Calving rates (measured a lactation failure)
increased significantly from 81 to 88% in a clinical trial assessing the effect of a L. sv. Hardjo
vaccine in beef cattle (Holroyd and Smith, 1976). A subsequent study also reported higher
weaning rates in vaccinated vs control cattle (Holroyd, 1980). No difference of reproductive
performance indicators (pregnancy, calving, stillbirth) were observed in beef cattle of one farm
in Brazil between sero-positive and sero-negative at the start of the mating season (DelFava et
al., 2004), but the study gave no indication of active challenge during the risk period.
Some caveats may be noted when attributing the above cited production effects from various
countries with serovars Hardjo (Hardjoprajitno, Hardjobovis) or Pomona (L. interrogans, L.
kirschneri). It was not always clear which specific genetic variant of Hardjo or Pomona was
2
http://beeflambnz.com/Documents/Farm/Management%20of%20beef%20cattle%20for%20high%20fertil
ity%20-%20Part%202.pdf
28
involved, thus differences between studies may be explained by genetic differences linked to
virulence factors.
6.1 Conclusions on production outcomes
Under typical weather conditions in New Zealand, clinical loss due to leptospirosis is generally
limited to sporadic young stock loss and abortions. However, excessive floods in warm periods
of the year can lead to outbreak-like increases of mortality. In contrast, lower growth rates and
reduced weaning rates appear to be common in deer and possibly, given the above
observations of seroprevalence, other livestock species. As seen in deer, the loss-value due to
such sub-optimal performance in apparently healthy animals can be several times higher than
the cost of whole-herd vaccination in even modestly exposed herds.
7. History of vaccine use in New Zealand
Vaccines against leptospirosis were introduced in New Zealand in the early 1970s by ScheringPlough Animal health followed by Pfizer in the 1990s (personal communication). A bivalent
(Hardjo/Pomona) vaccine started to become more widely used by dairy farmers in the early
1980s (Marshall and Chereshsky, 1996). However, only a small proportion of sheep (<1%), beef
(18%) or deer farmers (10%) adopt vaccination against leptospirosis presently. The only
commercial industries that generated a major uptake vaccination were dairy and pig farmers
(over 85%). The latter two industries are therefore briefly mentioned here.
Dairy farmers
Dairy cattle have been assumed to be the major source species for transmitting Leptospira to
humans in the 1970s and 1980s. Therefore, vaccination of dairy cattle was introduced in 1979,
widely propagated for controlling the disease in people in the 1980s, and followed by a drastic
decline of human cases in the 1990s (Marshall and Chereshsky, 1996).
The Health and Safety in Employment Act 1992 defines leptospirosis as a ‘significant hazard’.
The New Zealand Veterinary Association (NZVA) subsequently created Leptosure®, an initiative
for the control of leptospirosis beyond vaccination in the mid 1990s. A farmer booklet describes
the programme’s aims and functionality. The booklet can be downloaded from the Internet3.
Leptosure® is a national risk management programme developed by the New Zealand
Veterinary Association and the Society of Dairy Cattle Veterinarians to reduce the risk of human
leptospirosis infection on New Zealand dairy farms. It describes sources of infection for humans
and explains on-farm mitigation procedures. The programme is aimed at helping farmers to
develop a risk management plan (RMP), initially for dairy farms, and more recently, also for dry
stock.
Pig farmers
Pork Industry New Zealand (NZPork) in liaison with the NZ Food Safety agency (NZFSA) has
implemented a set of rules for movement and trade under the Animal Status Declaration (ASD)
for pigs. Since 01 March 2006, producers are obliged to fill an ASD form for every movement of
pigs from commercial properties, whether it is pigs for slaughter or other movements. The ASD
covers leptospirosis with the following rule4:
3
http://www.leptosure.co.nz/sites/default/files/domain18/Leptosure%20Green%20Farmer%20Booklet%202007.pdf
4
http://www.foodsafety.govt.nz/elibrary/industry/Animal_Status-Must_Completed.pdf
29
“A leptospirosis control programme requires vaccination of the breeding herd if present at least
every 6 months, and certification of the grower herd as ‘free of leptospirosis’ at least once every
12 months. Grower herd certification is based on the results of serological testing of a minimum
of 10 grower pigs either within two weeks of slaughter or at slaughter using the MAT (Micro
Agglutination Test) for Leptospira pomona. Interpretation of the results is required to determine
the status of the grower herd. This must be done by a registered veterinarian. Equivalence to the
above programme documented by a registered veterinarian is accepted.”
Thus, leptospirosis is well controlled in pigs on commercial production units. However,
uncertainties remain about the risk of human exposure from backyard piggeries and hobby
farmers. NZPork has commissioned a report by Massey “Small scale pig farming: practices and
obligations”5 that includes guidelines and recommendations about how to manage the risk of
infection for people in contact with pigs under such small scale systems. Farmers and
households are advised to vaccinate al pigs every six months.
8. Vaccine label claims and recommendations
The information to write this summary was obtained from labels approved by the NZFSA
available in http://www.foodsafety.govt.nz. Please refer to Annex III (vaccine summary) for
more detailed information.
8.1 Cattle
There are currently 9 vaccines registered for use in cattle in New Zealand: Leptavoid 2®,
Leptavoid 3®, Leptoshield®, Leptoshield 3®, Vaxall®, Cattlevax®, Ultravac 7®, Lepto 2-Way®, and
Lepto 3-Way®. All vaccines include Leptospira serovars Hardjo and Pomona, and vaccines with
postscript ‘3’ also include serovar Copenhageni. No vaccine includes serovar Ballum.
Purpose: In general all providers recommend the use of vaccine to prevent infection and urinary
shedding and note that vaccination is effective in previously non-exposed cattle. This implies
that vaccination after natural exposure is accepted as having lower efficacy.
Recommendations in common: Labels of all vaccines recommend two doses subcutaneously 4
to 6 weeks apart, followed by a single booster annually. Some of them recommend a booster
every 6 months where Leptospira is present at high endemic level (Vaxall®), or for multipathogen vaccines, where clostridium disease challenge is regarded to be exceptionally high
(Cattlevax®). Vaccination is generally recommended to be administered before the season of
high risk, generally in autumn to early summer. For breeding females, labels of Leptavoid-2®,
Leptavoid-3®, Leptoshield®, Vaxall®, and Ultravac-7® recommend applying the annual whole
herd booster one month before calving in order to increase antibodies in colostrum for
protecting new-born calves against infection with Leptospira.
5
http://www.nzpork.co.nz/LinkClick.aspx?fileticket=l9Kj6cs73SU%3D&tabid=123&mid=622
30
Calves XXX
Label recommendations that differ between providers: The recommended age for calf
vaccination differs between brands. Some labels claim that the vaccines are effective in the
presence of MDA and calves can therefore be vaccinated at one month of age. vaccination is
unlikely whereas others claim some degree of interference.
Maternal antibodies are unlikely to interfere with the response to vaccination in calves.
Leptoshield®, Leptoshield 3®, and Ultravac 7® claim to be efficacious in the presence of MDA,
and therefore calves may be vaccinated from 1 month of age. Two doses 4 to 6 weeks apart
should be applied. If a second vaccination is administered before 3 months of age, a single
booster dose “should” be administered 6 months later, at 8-9 months of age.
Maternal antibodies may interfere with the response to vaccination in calves.
Leptavoid 2®, Leptavoid 3®, and Cattlevax®: If vaccination is completed (i.e. sensitiser and
booster) before 6 months of age, a single booster dose is required at 6 month of age to ensure
protection for 12 months.
Vaxall®: If vaccination is completed before 6 months of age, a booster dose is required at 6
months of age, followed by a second dose 4 to 6 weeks later.
Lepto 2-Way®, and Lepto 3-Way®: The first vaccination course can start anywhere between 12
weeks of age and 4 weeks before 9 months of age, thus the first course should have been
completed by 9 months of age. However, in the case of a first course of vaccination starting at
12 weeks of age, it is essential to administer an additional booster at 6 - 9 months of age to align
with future herd vaccination. In all cases, two doses should be given 4 - 6 weeks apart and
finishing no later than 9 months of age.
8.2 Sheep
There are currently 2 vaccines registered for use in sheep in New Zealand: Leptavoid-2®, and
Leptoshield®. Purpose, dosage and administration are identical as described for cattle.
Purpose: For the active immunisation against leptospirosis (Leptavoid-2®) or for the prevention
of leptospirosis (Leptoshield®). No reference is made to the prevention of urinary shedding.
Recommendation: Two doses 4 to 6 weeks apart, before the season of high risk in autumn to
early summer. No differences exist between label recommendations for sheep.
Booster: Single dose annually.
Age at first vaccination of lambs: No detailed recommendations are given for lamb vaccination.
31
8.3 Deer
There are currently 3 vaccines registered for use in deer in New Zealand: Leptavoid-2®,
Leptavoid-3®, and Leptoshield®.
Purpose: For the active immunisation against leptospirosis (Leptavoid-2®, Leptavoid-3®) or as an
aid in the control of leptospirosis (Leptoshield®). The label of one product explicitly mentions
the prevention of urinary shedding (Leptavoid-3®).
Vaccination: Two doses 4 to 6 weeks apart, before the season of high risk from autumn to early
summer.
Booster: Single dose annually.
Age at first vaccination of fawns: No detailed recommendations are given for vaccination of
deer calves.
32
9. Host immune response after exposure
9.1 Background
The symptoms, severity and course of leptospirosis are very dependent on the relationship
between the infecting serovar and the animal host species. The disease tends to manifest in a
much less severe form when the animal is a maintenance or reservoir host for the particular
infecting serovar. For this reason, it is often useful to consider leptospirosis as a group of
diseases rather than as a single disease. Infections from the two serovars of main interest to
New Zealand’s livestock industry, Hardjobovis and Pomona, present differently. Hardjobovis is
considered to be in a maintenance host relationship with at least cattle and deer, and probably
sheep, in New Zealand, and therefore, the disease caused by this serovar may behave
differently to that of a Pomona infection. Ruminants were so far considered accidental hosts for
Pomona, and thus this serovar was expected to causes more severe disease than Hardjobovis.
However, recent serological findings of antibodies to Pomona being present in 10-14% of adult
beef cattle, sheep and deer in New Zealand suggest that these host species may be a reservoir
for Pomona. Notwithstanding this consideration, any discussions around the host responses
should differentiate the host adaptation to different serovars.
Leptospires colonise the kidneys of an infected host and are then shed into the environment via
the contaminated urine. From there, leptospires can enter a new host through cuts or abrasions
to the skin and through mucosal tissue. In some instances Leptospira reside in the genital tract
and can be transmitted through reproductive fluids (Ellis et al., 1986). Once in the bloodstream,
they circulate for approximately 3-7 days before colonising the kidneys although the time varies
dependent on the challenge dose and strain (Faine et al., 1999). The extent of other organ
involvement varies according to the age of the animal and the serovar involved. Likewise,
symptoms can range from sub-clinical to death dependent on the infecting serovar and the host
animal. If an animal survives the initial stage of infection, Leptospira will colonise the kidneys
and from there the bacteria are shed in the urine.
In New Zealand, serovars such as Pomona and Copenhageni are considered to be sporadic
infections. As opposed to a host-adapted strain, e.g. Hardjobovis, these serovars tend to cause a
more severe clinical illness. Whilst high numbers of Leptospira can be shed from the colonised
kidneys in the urine, the period of shedding tends to be shorter lived than in an animal where
the serovar is considered host-adapted. In situations where the animal species acts as a
reservoir host for a particular serovar, the Leptospira are maintained in the flock/herd.
Transmission of infection from more mature animals to younger stock is consequently likely to
be more predictable and cyclical than those of sporadic leptospiral infections. Thus, the
dynamics of natural exposure in domesticated herds/flocks is influenced by the host and the
serovar as well as by farm management practices and environmental conditions. Also, as
opposed to the human situation where leptospirosis is incidental, immunological responses to
infection or vaccination as well as control measures in naturally infected animal populations,
can additionally be interpreted in the context of a herd setting.
9.2 Immunological responses mechanisms
Though the immunological response types may not necessarily be independent, it is convenient
to discuss them under two separate categories; humoral (antibody production) and cell
mediated immunity (CMI). Most ruminant leptospirosis research has used cattle as the host
species so the majority of experimental evidence is derived from this model. Whilst there is
evidence that the host’s primary immunological response to leptospiral infections is humoral
and that passive protection has been demonstrated effective in a number of challenge trials
(Flint and Liardet, 1980; Marshall et al., 1982; Palit et al., 1996), the duration of effective passive
33
protection and the role of cell mediated immunity is much less clear. This is particularly the case
with Hardjobovis infections in cattle.
9.3 Innate immunity and the influence of age and genetic background on resistance
Any innate resistance in naïve hosts is thought to be limited to a humoral response with the
host already possessing antibodies that will react to the same agglutinating leptospiral epitopes
used in the serological classification system for Leptospira (Faine et al., 1999) or, protection via
complement (Cinco, 2010; Fraga et al., 2011). The lipopolysaccharide (LPS) of the leptospire’s
outer cell surface is highly antigenic (Faine et al., 1999) and is the foundation of the
classification system that divides Leptospira into serogroups and serovars. Although not
exclusively so, it is LPS that is the dominant class of antigen against which a host mounts a
humoral response and passive transfer of protection by antibodies against the LPS or
monoclonal antibodies has been demonstrated to be protective (Faine et al., 1999).
Different mammalian species are born at various stages of maturation and immune competence
and this affects the susceptibility of animals to leptospiral infection. For example, it is standard
practice for young hamsters and guinea pigs which possess immature B cells (Faine et al., 1999)
to be used for routine vaccine testing (Faine, 1982) as they are much more susceptible to
leptospiral infections than the adults and, whilst adult mice and rabbits are resistant, their
immature young demonstrate variable susceptibility (Faine et al., 1999). The severity of an
established infection can also vary between adults and young with milder responses tending to
be seen with increasing age (Fennestad, 1963) e.g. “red water” in calves infected with Pomona.
Genetic lineage may also play a role in resistance/susceptibility to leptospirosis. Certain lines of
pigs have been shown to be less susceptible to leptospiral infection (Przytulski and
Porzeczkowska, 1980) providing evidence that genetic background also plays a role in
resistance, but the mechanism by which this is effected is unclear.
9.4 Measurement of humoral response
The microscopic agglutination test (MAT) remains a gold standard and is still used extensively
for detecting any antibodies. Though not specific for any particular class of antibody (Faine et
al., 1999), MAT is thought primarily to detect a mixture of IgM and IgG (Morris and Hussaini,
1974). Although a number of other methods have been trialled for the early detection of
leptospiral antibodies e.g. haemolytic test, indirect haemagglutination assay, indirect
immunofluorescence, indirect IgM ELISA, IgM dot-ELISA, immobilized antigen dipstick and
lateral flow assays, (Faine, 1982; Effler et al., 2002), comparative evaluation suggests further
development is required, particularly around the sensitivity and specificity of detection in early
stages of the disease. The antigens employed in these techniques all involve LPS or chemical
related derivatives of these (Faine et al., 1999). Early production of IgM antibody may be
detected by anti-IgM ELISA. However, these antibodies can be less specific than the latterproduced IgG1 antibodies and thus react against a variety of serovars and are therefore less
reliable for identifying the infecting strain (Faine et al., 1999). This is also the reason why in the
very early stages of infection the predominant titre may appear to be to a strain other than the
infecting serovar. Cross-reactions are more common in closely related serovars however, as the
infection progresses, the false titre readings drop and are replaced by higher titres to the
infecting strain. This highlights the importance of paired sera to demonstrate a rising titre for
diagnostic purposes in early stages of infection.
Age is another factor influencing the serological response with experimental results suggesting a
tendency for cross-reaction to decrease with increasing age of calves, thus correlating with a
maturation of the immune system (Fennestad, 1963). It is not possible to distinguish between
the genetically and serologically very closely related serovars Hardjobovis and Balcanica (NZ
34
possum variety). Cattle act as an incidental host for Balcanica and therefore, unlike Hardjobovis,
the infection is not spread amongst the herd highlighting the advantage offered by interpreting
titres in the herd setting under certain circumstances.
9.5 Humoral immune response
Immunoglobulins are usually produced 2-10 days after the onset of infection, dependent on the
animal species and the individual’s immunological competence, the infecting serovar and the
infective dose (Faine et al., 1999). IgM antibodies are generally the first to be produced and are
later replaced by IgG1 titres from about two weeks onwards (Faine, 1982). The level of antibody
response is variable depending on the genetic background of the individual, the species and age
of the animal and on the infecting serovar: host-adapted strains such as Hardjobovis in cattle
tend to induce lower levels of antibody response in the host that can make interpretation of
titre data to this serovar difficult to interpret. In situations where leptospirosis circulates in
herds, animals with antibodies may get anamnestic boosting sufficient to prevent re-infection
but insufficient to register as a significant rise in titre level. This can lead to the pattern shown in
Figure 9.1a: the peaked distribution is typically found in maintenance host-adapted Leptospira
serovars e.g. Hardjobovis in cattle, sheep and deer. The serovar is maintained in a mixed-aged
herd/flock. The peak antibody titre settles at a median as a result of antibody decay and rate of
new infection following natural challenge. On the other hand, regressing titre distributions are
more typical of the tail-end of an incidental infection in a non-maintenance host. The pattern for
Pomona in cattle, deer and sheep (Figure 9.1b) suggests that such incidental infections with
Pomona seem to occur frequently in these species. Leptospira can be shed intermittently by
chronic carriers for lengthy periods of time (Flint and Liardet, 1980; Hancock et al., 1984; Smith
et al., 1994; Ayanegui-Alcerreca, 2006) or for life (Ellis et al., 2000) and can even be isolated in
urine from hosts that demonstrate little or no detectable titre (<1:24) when titrated against the
infecting serovar (Mackintosh et al., 1980; Faine et al., 1999; Dorjee et al., 2009).
Whether the infection is natural or artificial or, whether the antibodies are a response to
challenge rather than vaccination can also influence the immunological response. For example,
the route of artificial challenge (e.g. intraperitoneal, intramuscular, conjunctival or
nasopharyngeal mucosa) and the infective dose may have a bearing on the serological response
(Fennestad, 1963). However, it should be noted that some artificial methods of infection e.g.
intraperitoneal via syringe, can guarantee a more uniform challenge than the
conjunctival/nasopharyngeal route where blinking and sneezing by the animal can affect actual
dosage: a smaller dose taking longer to establish signs of disease. The antibodies raised to
infection are specific with cross-protection to re-infection only afforded by the same or very
closely related serovars (Faine et al., 1999) e.g. Hardjoprajitno and Hardjobovis, and an
important factor when considering vaccination practices. It is these agglutinating antibodies that
have been used extensively as a measure of exposure, diseases status in animals and vaccine
efficacy and have been used as a proxy for protection. Variant strains of the same serovar may
also illicit slightly different serological reactions i.e. some produce a greater degree of reactivity
with MAT (Collins-Emerson, JM., personal comm.). It is suggested therefore, that local strains of
Leptospira be considered for use in MAT and for vaccine production.
Of the three major livestock species of interest in New Zealand, it is cattle in which the majority
of experimental trials and hence experimental data exist and many of these trials involve
artificial challenge and vaccination. The response to challenge, whether artificial or natural will
be discussed in this section with vaccination titres being covered later in the report.
35
(a) HARDJO
(b) POMONA
Figure 9.1: Frequency distribution of MAT titres to Hardjobovis (a) and Pomona (b) from
samples from mixed age breeding stock from 116 beef, 98 deer and 161 sheep farms.
Titres in natural infection usually peak somewhere between a week and two months after
infection (Fennestad, 1963; Dixon, 1983; Smith et al., 1994) then gradually decline however, the
peak can vary considerably in magnitude (1:3200 to undetectable in cattle with Hardjobovis
infection, (Carter et al., 1982; Dixon, 1983; Smith et al., 1994). There is a tendency for younger
animals to develop higher titres than older ones (Fennestad, 1963). As titres to Hardjobovis may
not attain high levels, determining an animal’s infection status or distinguishing between
infection versus vaccination titres, is not always straight forward. Vaccination titres can be lower
than those induced by infection (Kiesel and Dacres, 1959; Strother, 1974). Serovars causing
more severe infections e.g. Pomona and Copenhageni, tend to produce higher titres than
Hardjobovis infections (Carter et al., 1982; Faine et al., 1999; Ayanegui-Alcerreca, 2006). It
should be noted that serological data from many earlier overseas studies were reported prior to
the realisation that serovar Hardjo comprised two different organisms i.e. L. interrogans serovar
Hardjoprajitno and L. borgpetersenii serovar Hardjobovis and that interpretation of results is
thus complicated as the two serovars may not behave in exactly the same manner. In New
36
Zealand, Hardjobovis antibodies were found to gradually decline over a period of 11 months
(Dixon, 1983).
During acute infection leptospires can cross the placental and invade the fetus (Faine, 1982) and
it has been demonstrated that bovine (Fennestad and Borgpetersen, 1962; Ellis et al., 1978) and
ovine fetuses (Kirkbride and Johnson, 1989) that are sufficiently mature are able to produce
antibodies. This means that calves/lambs may be born with pre-colostral titres to Leptospira.
9.6 Maternally-acquired Immunity
The placental structure in ruminants means that there is no transfer of protective antibodies
across the placenta but that passive transfer is accomplished by ingestion of colostrum shortly
after birth (Stelwagen et al., 2009). Passive immunity is achieved in the first couple of days after
birth whilst the gut of the newborn is still permeable to the large immunoglobulin molecules in
the colostrum. The permeability of the gut decreased rapidly thereafter. Calves develop peak
titres around 11 hours after birth and a single feed of colostrum is required to achieve this
(Hellstrom, 1978). Not all calves demonstrated antibodies in this trial although their dams were
seropositive. However, when colostrum from a seropositive dam was fed to a calf that was
seronegative 16 hours after birth, that calve seroconverted suggesting its initial seronegative
status was due to unsuccessful suckling at birth. The duration of the maternal colostral
antibodies in the neonate and the protection offered is dependent on the size of the initial titre
and how long antibodies survive in the body before being catabolised. The half-life of IgG1 was
estimated by Nielsen et al., (1978) to be around 18 days. The predominant immunoglobulin in
colostrum is IgG1 (Stelwagen et al., 2009) and in cows is transported from the blood into the
milk via the mammary gland peaking 2 to 3 weeks before parturition (Salmon, 1999). This time
factor needs consideration when vaccinating dams with the aim of conferring maternal
immunity to the young. With the transport into the mammary gland comes a corresponding
drop in titre levels in the dam recovering to pre-calving titres about three weeks after calving
(Hellstrom, 1978). Initial titres in their calves are usually higher than those in their dam
(Hellstrom, 1978).
The degree of protection offered, as measured by MAT, and the duration of immunity of
maternally-derived antibodies varies between studies but mostly wanes by six months of age in
cattle (Hellstrom, 1978). The degree of protection offered the young is also dependent on
farming practices. Young calves sent for off-farm grazing were found to be infected on their
return to the main herd at about 6 months of age (Pegram et al., 1998) and infection could be
found in deer as young as three months of age (Ayanegui-Alcerreca, 2006).
9.7 Cell-mediated immunity
The weight of experimental evidence supports antibody production as the primary immune
response to infection. In cattle where Hardjobovis infection is widespread and usually chronic,
there is also supporting evidence that cellular immunity may play a role in long term protection
from re-infections with that particular serovar (Adler and De la Peña Moctezuma, 2010).
However, with other species there is very little experimental data on the role of cell mediated
immunity and the situation remains unclear. High antibody titres have not necessarily been
shown to be protective in cattle yet, cattle that have negligible or undetectable antibody titres
to Hardjobovis after vaccination have been demonstrated to be immune to infection (Adler and
De la Peña Moctezuma, 2010).
Experimental work has demonstrated cell-mediated immunity (Type 1 immunity) is likely to play
a role in the long term protection to infection or re-infection in cattle. This being an alternate
37
pathway to that of antibody production in the humoral system, it is not inconsistent with the
observation of animals with low MAT antibody titres still demonstrating protection against
infection. The majority of work has been carried out in cattle in vaccination trials. Like MAT
titres, the magnitude of response does vary between individuals but, there is a pronounced
difference in the response between groups of animals that experience natural infection versus
vaccination: Animals receiving vaccine demonstrated a more pronounced response (Naiman et
al., 2002) which peaked at two months after the second dose of vaccine (Naiman et al., 2001). In
the presence of antigen, CD4 T cells in vaccinated cattle were demonstrated to manufacture
IFN-γ, which itself was produced by the T cells; CD4+
and WC1+ γ (Naiman et al., 2002;
Blumerman et al., 2007). The in vitro memory response of these γ T cells was reported to be
maintained for one year at a minimum whilst with some animals this was out to two years in the
absence of any boosting (Blumerman et al., 2007). IFN-γ activates macrophages and promotes
IgG2 immunoglobulin (Naiman et al., 2002). Under laboratory conditions, CD4+
T cells were
also shown to be necessary for good γ T cells response (Blumerman et al., 2007). Although
Natural Killer (NK) cells are known to be involved with the innate immune system, ex vivo
experiments conducted by Zuerner et al., (2011) demonstrated that NK cells carrying the CD355
marker and sourced from vaccinated animals showed an IFN-γ recall response when exposed to
L. borgpetersenii serovar Hardjobovis. NK cells from the non-vaccinated control animals failed to
illicit such a response. This experiment provides support for NK cells having an immunological
memory and playing a role in the acquired immune response.
9.8 Conclusions
The host’s primary response to a leptospiral infection is humoral and the antibodies produced
are specific for the infecting serovar. Thus there is little, if any, cross-protection from
subsequent infection with a different serovar. Longevity of protection by these antibodies is
dependent on the initial titre peak and hence duration of detectable titres, the serovar and the
degree of challenge in subsequent exposure. In the case of Hardjo infections in cattle, cellmediated immunity may also play role in protection. In new-born ruminant animals, the primary
mechanism for protection against leptospiral infection is effected by the passive transfer of
maternal antibodies against Leptospira in the colostrum: the level of antibody protection, as
measured by MAT, is dependent on the antibody level in the dam. Experimental data suggest
that MDA has waned by six months of age and in a high challenge scenario, many calves on a
farm will be susceptible to infection at an earlier age.
38
10. Evidence of vaccine efficacy to prevent urinary shedding
The antibody response following vaccination has been measured in most trials of vaccine
efficacy. However, given the described uncertainty surrounding the relationship between
serological response as measured by the MAT and protection against challenge, in this section
the focus is on the evidence of vaccine efficacy to prevent shedding of leptospires.
Appendix II summarises results of vaccine efficacy studies from the published literature. For
completeness, evidence from serological data is included in the summary of measures of
efficacy. Although additional unpublished data exist from small trials carried out by the
pharmaceutical companies to support safety and efficacy claims for product registration, these
are in the form of brief internal reports or summary information. They have not been peerreviewed and are thus not included in the appendix. However, where relevant, their findings are
discussed below.
Published studies are difficult to compare directly, as they include natural and experimental
infection challenges and vary in dose of challenge and in the leptospiral serovars used in the
vaccine and for challenge. Additionally, there are differences in age at vaccination, interval
between vaccination and challenge and method of measuring and quantifying leptospiral
shedding. Route of challenge also varies between the studies: intravenous, intraperitoneal,
conjunctival, oral and intranasal methods of delivering a challenge dose have all been applied in
the studies reported here. However, recent OIE guidelines recommend “immunity should be
tested by challenge with virulent field strains of each serovar by natural routes of infection, i.e.
by conjunctival and/or vaginal challenge” (OIE, 2008).
The vaccines administered in the reported trials range from mono- to multivalent preparations
and use different adjuvants and strains of the organism, although often in the literature there is
little detail on the vaccine preparation itself.
Key findings of some of the individual trials that measured efficacy of vaccine to prevent urinary
shedding are briefly summarised here.
10.1 Vaccination challenge trials (cattle)
Early studies of vaccine efficacy were carried out with preparations containing serovar Pomona.
Gillespie and Kenzy (1958a) demonstrated that urinary shedding could be prevented in heifers
using vaccines containing a killed suspension of serovar Pomona. Twelve heifers were
vaccinated at 6-8 months of age and, along with five controls, were experimentally challenged 8
months later with urine containing serovar Pomona from shedder cattle via the conjunctival
route and in drinking water. Urine was classified for leptospiral shedding by darkfield
examination or by ‘laboratory animal’ inoculation. Shedding was identified in 1/12 vaccinates
and 5/5 controls.
Ris and Hamel (1979) assessed a commercial monovalent Pomona vaccine (A) and experimental
Pomona vaccines prepared with different adjuvants (B and C) in three groups of four 9-monthold heifers, comparing them to a control group of four heifers. Experimental challenge was by
the intramuscular route 47 weeks later. Urinary shedding of leptospires, as assessed by culture,
was prevented in all of the vaccinates but detected in all of the controls. Several studies
reported efficacy of vaccines using a Pomona strain for challenge (McDonald and Rudge, 1957;
Gillespie and Kenzy, 1958a; Kiesel and Dacres, 1959; Stalheim, 1968; Strother, 1974; Marshall et
al., 1982). The key aspects of the studies and findings are summarised in Annex II.
39
Studies in cattle have similarly examined the efficacy of vaccination with a monovalent
preparation of serovar Hardjobovis or Hardjoprajitno to prevent urinary shedding of leptospires.
In a US study, Bolin et al. (2001) vaccinated two groups of eight 8-12 month old heifers with two
different monovalent Hardjobovis vaccines - a commercially available vaccine (A) and a
reference vaccine (B) - keeping a third group of eight heifers as controls. The heifers were
experimentally challenged four months later with a US strain of serovar Hardjobovis, by
conjunctival instillation or intraperitoneal inoculation. Vaccine A was shown to prevent urinary
shedding and renal colonisation in 8/8 heifers. In contrast, all heifers inoculated with vaccine B
were urine and tissue positive. The study also showed differences in shedding outcomes
between the different routes of leptospiral challenge. Challenge via the conjunctival route
resulted in leptospiruria in 4/4 controls compared to 2/4 controls challenged intraperitoneally.
Leptospires were identified in the kidneys of all controls.
More recently, Zuerner et al. (2011) assessed the efficacy of a monovalent Hardjobovis vaccine
(Mono1) to prevent urinary shedding in Holstein steers when challenged three months later
with serovar Hardjobovis by the conjunctival route. None of the eight vaccinates and 4/4
controls were urine culture positive following challenge. However, the presence of leptospires
in urine was also assessed by PCR, which identified 6/8 vaccinates and 4/4 controls as positive.
This is one of the few cattle studies to use PCR to identify urinary shedding. Although identifying
bacterial DNA does indicate at least transient colonisation of the kidney, the technique cannot
distinguish between live and dead bacteria. The relevance of the finding to transmission of
infection to other animals or humans is thus unknown.
Efficacy studies of bivalent vaccines containing Hardjobovis and Pomona serovars have similarly
demonstrated efficacy of the vaccines in preventing urinary shedding in cattle. The published
literature includes studies carried out in New Zealand, such as those of Marshall et al., who
examined the efficacy of a serovar Hardjo/Pomona vaccine. The first study (Marshall et al.,
1979b) involved nine calves vaccinated at 3-4 months old and given a booster vaccination six
weeks later, and ten unvaccinated controls. The calves were exposed, seven months after
vaccination, to cattle known to be shedding Hardjo and urine was monitored by culture and
dark-ground microscopy over a period of four months. None of the vaccinates and 6/10 of the
controls shed Hardjo in urine.
In the second study (Marshall et al., 1982), the efficacy of the Pomona component of the same
vaccine was assessed in six-month old heifers, this time using subcutaneous challenge with
serovar Pomona at 19 days post-vaccination rather than natural challenge. None of the 11
vaccinates and 8/11 unvaccinated controls yielded positive urine cultures during 32 days of
follow-up.
10.2 Vaccination after exposure
The majority of natural and experimental exposure studies have examined the efficacy of
vaccination when administered before challenge. However, one study (Hancock et al., 1984), in
which cattle already shedding leptospires in urine were vaccinated, was identified. A group of 19
two-year-old heifers, 9 (47%) of which were leptospiruric, was vaccinated with a single dose and
results of urine culture 22 weeks later were compared to those from a control group of 22
heifers, of which 15 (68%) were initially leptospiruric. In the vaccinated group, 4/15 (27%) were
leptospiruric 22 weeks later, compared to 4/9 (44%) of the controls. No explanation is given in
the manuscript to account for the loss of four of vaccinates and seven controls to follow-up,
other than a statement that all animals were not made available during the sampling periods.
More information would have been useful, for example to confirm that the animals were still in
the herd or whether some animals may have been culled due to reproductive failure.
Nevertheless, the findings supported the overall conclusion of the study that there is no
40
evidence that use of vaccination in already infected cattle is effective in preventing urinary
shedding.
10.3 Age at vaccination (cattle)
One of the earliest published trials of vaccine efficacy examined the efficacy of three vaccine
preparations when administered to three different age groups of cattle (Gillespie and Kenzy,
1958a). Each preparation contained a different bacterin of a killed suspension of serovar
Pomona and experimental challenge, using urine prepared from shedder cattle, was by the
conjunctival and intranasal routes as well as by contamination of drinking water. Each age group
of animals (1-2 months, 3-5 and 6-8 months of age) was matched with a non-vaccinated control
group of the same age. A difference in response to vaccination, as measured by the successful
culture of leptospires from urine, was seen between the animals vaccinated at 1-2 months
(Group A) and 3-5 months (Group B) of age when compared to those vaccinated at 7-8 months
of age (Group C). Combining results of the different vaccine preparations together, leptospiruria
was confirmed in 5/9 vaccinates and 5/6 controls, 4/8 vaccinates and 3/3 controls and 1/12
vaccinates and 4/5 controls in Groups A, B and C respectively. Leptospira were determined at a
semi-quantitative scale, with the authors concluding that ‘vaccinated cattle that did excrete
leptospires in the urine often shed appreciably fewer than the controls’. While the older (Group
C) animals were known to come from infection-free herds, the immune status of the calves was
known only with respect to MAT titres, as they were sourced through a local stock buyer.
Nevertheless, in this trial the Pomona vaccines appeared more efficacious against urinary
shedding in older than younger animals.
Schollum and Marshall (1985) examined the serological responses of ten initially sero-negative
three-month-old calves to vaccination with a commercial bivalent Hardjo/Pomona preparation.
MAT titres to Pomona and Hardjo were compared to those from 35 calves vaccinated at six
months of age. Thirty percent of calves vaccinated at the younger age had a positive MAT titre
(1:24) to Pomona while 40% were MAT positive to Hardjo. In contrast, 94% and 86% of the
animals vaccinated at 6 months old were MAT positive to Pomona and Hardjo, respectively. It
was concluded that vaccination at 3 months of age caused a poorer immune response than
vaccination at 6 months. However, there was no challenge to allow comparison of the efficacy
of vaccination at either age to control urinary shedding, nor were there control groups in this
study, hence there was no information of natural challenge in those mobs that could have
contributed to higher antibody in the calves vaccinated at the higher age. As previously
discussed, data on serology alone allows limited inference to be made on the protective efficacy
of vaccination.
By contrast, in a challenge trial designed to develop a guinea pig potency test, Goddard et al.
(1986) vaccinated groups of calves aged 12-28 days with graded doses of field vaccines,
challenging the vaccinates and a control group of five calves intravenously with serovar Hardjo.
Using the vaccines at full field dose, 0/10 calves were kidney culture positive compared to 5/5
controls.
Results from three studies carried out to assess the efficacy of vaccination in calves from four
weeks of age was reported in a conference abstract (Gallo et al., 2010). Thirty-one MAT
negative month-old calves were vaccinated and given a booster 4-6 weeks later with a Hardjo
vaccine while 19 remained as unvaccinated controls. Challenge with serovar Hardjo was by the
conjunctival route at three weeks or 12 months after the initial booster vaccination, or four
months after a 12-month booster vaccination. No vaccinates were leptospiruric or positive to
culture of kidneys 7 weeks after challenge, while all controls were urine or kidney culture
positive.
41
The above studies were carried out in animals with no detectable MDA. These studies
demonstrate that, in the absence of MDA, vaccination against Leptospira is effective as early as
4 weeks of age. The effect of the potential interference of MDA on vaccination response in
young animals is discussed specifically in section 9.5.
10.4 Vaccine efficacy in sheep and deer
A single sheep study (Marshall et al., 1979a) was identified by the systematic literature search.
The research was carried out in New Zealand, and involved 19 Romney ewes aged 7-9 months.
Nine were vaccinated twice, one month apart, with a bivalent Pomona/Hardjo preparation and
10 remained as untreated controls. Challenge six weeks later, with a bovine isolate of serovar
Hardjo, was by the intraperitoneal or the intramuscular route, while infection status was
established by culture of kidneys at post-mortem three weeks after challenge. Two vaccinates
and all controls were Leptospira positive. A notable additional finding from this study was that
two of the vaccinates which resisted challenge showed no MAT response to vaccination, and
two with titres rising from 24 to 96 between weeks 12 and 13 were culture negative. Although
demonstrating the efficacy of vaccine to prevent kidney colonisation, the short timescale of the
trial meant the study does not provide any evidence of the duration of vaccine induced
immunity in sheep.
In deer, vaccination has been shown to prevent urinary shedding of leptospires in a natural
challenge situation (Subharat et al., 2012). The study, carried out in five commercial deer herds
in 2007, followed on from the research of Ayanegui-Alcerreca (2006), who found vaccination in
herds naturally infected with serovars Hardjo and Pomona reduced urinary shedding by 44%. In
the 2007 study, 435 three-month old deer were treated with streptomycin and 217 were then
inoculated with a bivalent Hardjo and Pomona vaccine while 218 were maintained as
unvaccinated controls. Challenge was natural, with trial animals mixed with deer infected with
Hardjo on the same farm. Urine from 110 female deer from each trial group was monitored for
shedding using culture and PCR, with positive PCR results (8/34) seen only in control animals on
two farms six months later. On one farm 1/9 controls were culture positive. Although the
proportion of controls in which shedding was detected by culture appears low, sampling of the
deer mixed with the trial animals found shedding rates of up to 83%, illustrating that challenge
was occurring.
10.5 Vaccination of dams to protect offspring
Protection of calves in their first month of life by vaccine-induced maternal antibody has been
demonstrated in cattle in New Zealand (McDonald and Rudge, 1957). The study involved 26
calves whose dams had been vaccinated in the last 2 months of pregnancy and 20 control
calves. The calves were experimentally challenged with serovar Pomona at 10 days (Experiment
1) and 4 weeks old (Experiment 2) and monitored for leptospiruria by dark-field microscopy,
over the following 6 weeks. In Experiment 1, 0/11 calves from vaccinated dams and 5/10 control
calves, and in Experiment 2, 1/15 calves from vaccinated dams and 7/10 control calves were
leptospiruric. The trial suggested that calves tended to remain resistant to infection up to 4
weeks of age due to MDA induced by vaccinating dams.
A study in which one group of calves from vaccinated dams were monitored for Hardjo MAT
titres from birth found evidence of maternally-derived antibody persistence until 12 weeks of
age (Palit et al., 1991). The study was not designed to demonstrate protection from challenge
per se in calves born from vaccinated dams, thus limiting the inference on the longevity of
protection via passive immunity that can be drawn from these data.
42
The optimal timing of dam vaccination for calf protection was assessed in a report by Virbac
New Zealand Ltd. (Pulford, 2006), using results from an in-house study that showed lower levels
of MAT Hardjo titres in new-born calves of dams vaccinated less than 50 days compared to
more than 50 days before calving. Combining these results with additional serological data from
new-born calves of dams vaccinated between 54 and 90 days pre-calving led to the conclusion
that, for optimal calf immunity, dam vaccination should be carried out at least 70 days before
calving. Note, however, that these studies were again based only on examination of serum
antibody levels, rather than protection from challenge.
The significance of the timing of dam vaccination, however, lies in the potential for persistent
MDA in calves to influence the response to leptospirosis vaccination (see 9.3(ii)).
10.6 Interference by maternally derived antibody (MDA) with vaccination
As described earlier, the presence of serovar-specific antibodies measured by ELISA or MAT
indicates that exposure had occurred at least one week prior and that resistance to new
infection is likely. However, the absence of such antibody does not indicate that an animal is
susceptible (non-resistant) as challenge studies suggest (Marshall et al., 1979b). The following
review should be read with this caveat in mind.
Maternally derived antibodies (MDA) are potentially present in offspring either when there is (i)
a high level of natural challenge (Hellstrom, 1978), or when (ii) the dam has been vaccinated
(Ayanegui-Alcerreca, 2006). MDA potentially interfere with vaccination (Ankenbauer-Perkins,
2000) but evidence about live-vaccines exists to the contrary, suggesting that vaccine efficacy
may NOT depend on an absence of MDA (Woolums, 2007). However, this inference may not be
equally valid for killed vaccines such as all currently available leptospirosis vaccines. Thus
vaccination of offspring in the presence of MDA may (or may not) reduce vaccine efficacy.
(i) Following a high level of natural challenge, the decay of naturally acquired maternal MAT
antibody in calves from a population of dams at high endemic level of Leptospira sv. Hardjo and
Pomona was described in detail by Hellstrom (1978). Over 90% newborn calves acquired MDA
after suckling sero-positive dams. Titres declined with a half-life of 15-17 days, most calves were
MAT sero-negative at 100 days of age, and all were negative at 190 days. This was equivalent to
a decay rate of 3.5% per day. Calf cohorts were followed until new infections were detected by
MAT resulting in most infections at about 12 months of age (Hellstrom, 1978). New, natural
infection resulted in high titres within 14 days of exposure which decayed down to 38% in the
first, to 11% in the second year after exposure, and by 5% per year thereafter.
CATTLE: If a continuously-high natural challenge of new-born calves is assumed, under these
circumstances, the proportions of susceptible, MDA-protected and infected calves from birth to
two years of age would be as shown in Figure 9.2 (upper). The model assumes that colostrum
acquired MDA decay to 100 days of age by which most calves are susceptible and that most
infections occur from about 100 – 200 days with 20% being infected at about 3.5 months of age.
Consequently, the peak of susceptibility, and therefore most vulnerable time for infection would
be around 40 – 110 days of age. Assuming that MDA negatively affects vaccine efficacy,
vaccination would be scheduled at about 60-90 days for optimal efficacy. However, the true
susceptible age may be somewhat later: Hellstrom’s data (1978) indicated that calves were
resistant to experimental challenge up to 3 months after the loss of MDA-induced MAT titres.
In endemic environments where MDA is assumed to be present, calves appear to be susceptible
to infection as early as 3 months of age. In an observational study on age at first natural
challenge, MAT titres of 1:96 and higher in 13 calf mobs of 11 vaccinated dairy herds were
evaluated (Pegram et al., 1998). The calves were sampled before 6 months of age and had not
yet been vaccinated. Titres were too high to be considered due to maternally derived antibodies
43
(MDA) and calves were considered too old (>3 months) to still have MDA. The natural challenge
was suspected to have occurred in mobs while grazing at run-offs at external farm locations. No
antibodies were found in age-equivalent calves at the home farm (Pegram et al., 1998). A 1980
study, when screening calves for a vaccine efficacy study, found five 6-month-old calves that
were already shedding leptospires in urine before first vaccination (Flint and Liardet, 1980).
New data from a small scale observational study tend to indicate that herds vaccinating dairy
calves for the first time before the age of 3 months experienced a lower rate of shedding in
adult cows than did herds that vaccinated calves after 3 months of age (Parramore et al., 2011).
These data require confirmation, as the age of vaccination was based on the recall of farmers,
not actual observation. If confirmed, the data suggest that calves were naturally exposed as
early as 1-3 months of age even though whole-herd vaccination had been practiced annually for
several years.
MDA
Suceptible
Infected
100%
1–3.5m
80%
60%
40%
20%
0%
0
50
100
150
200
250
Age (days)
MDA
100%
300
Suceptible
350
400
Infected
1 - 5m
80%
60%
40%
20%
0%
0
50
100
150
200
250
300
350
400
Age (days)
Figure 9.2: Theoretical high (upper) and low (lower) challenge scenarios (2 vs 1 Table 9.1) – expected
proportions of calves susceptible and infected assuming decay of MDA (Hellstrom, 1978) and a 2-fold
higher (upper) than reported (lower) (Hellstrom, 1978) natural challenge of 0.1-1.5% of susceptible calves
getting infected per day: MDA decay to 100 days by which most calves are susceptible; >20% infected
from 107 days onwards; most susceptible can be expected at about 1-3 months of age before natural
infection takes off.
DEER: Based on sero-prevalence of calf cohorts, Ayenegui-Alcerreca (2006) reported natural
exposure of deer earlier than 3 months of age on one farm, and later than 6 months on another
farm. It was concluded that environmental conditions as well as MDA-decay determined the age
at which animals were infected.
SHEEP: On a farm that experienced a clinical leptospirosis outbreak following summer floods in
2004, 100 lambs, 100 2-tooths, and 100 ewes were followed serologically for 3-12 months with
samples taken in 2-months intervals (Dorjee et al., 2005). In the presence of natural challenge in
2-tooths and adult ewes, lambs did not markedly sero-convert until after 10 months of age
(Figure 9.3).
44
POMONA
35%
HARDJO
Prevalence (cutoff 1:48)
30%
25%
20%
15%
10%
5%
0%
123
187
242
326
379
491
Age of lambs (days)
Figure 9.3: MAT sero-prevalence of Hardjo and Pomona in lamb cohorts born after an
outbreak of clinical leptospirosis (Dorjee et al., 2005)
Considering that natural challenge of offspring may occur rather sooner or later, the scenario of
Figure 9.2 was modified to compare the impact of a fast or slow MDA decay and high or low
infection pressure on the time that at least 50% offspring are susceptible and the time until 20%
young stock were infected (Table 10.1): if Hellstrom’s (1978) MDA decay reflected true loss of
resistance, a low infection pressure would provide a time window of 24 – 159 days during which
most animals would be susceptible and less than 20% were infected, i.e. indicating the “optimal
vaccination window”. At high infection pressure, this window would decrease to 24 – 107 days.
If MDA-induced resistance lasted twice as long as indicated by MAT titres, the grace period
before vaccination could start would reduce to 47 days regardless of infection pressure, and the
maximum time until which the first two vaccinations would have to be completed would be 207
days at low and 139 days of age at high infection pressure. Thus the most critical scenario would
call for vaccination to begin near the age of 1.5 months and for application of the booster by 3
months of age at latest.
Table 10.1: Model scenarios of two periods of MDA protection against infection (100d,
200d) and two levels of infection pressure (low, high) impacting on the proportion
infected (time to 20% infected) and the duration of having more than 50% animals
susceptible, hence responding to vaccination assuming MDA interfere negatively with
vaccine efficacy.
Scenario MDA decay
Infection pressure
Time to 20% infected >50% Susceptible
1
95% to 100d
Low
159 d
24 – 204 d
2
95% to 100d
High
107 d
24 – 137 d
3
95% to 200d
Low
207 d
46 – 241 d
4
95% to 200d
High
139 d
47 – 161 d
(ii) For circumstances where the dam has been vaccinated, a systematic search of the
published literature identified only one challenge study (Palit et al., 1991) which had the specific
aim to assess the influence of maternal antibody on the efficacy of vaccination to prevent
urinary shedding. The study involved calves born from initially sero-negative cross-bred
beef/dairy cows vaccinated pre-calving with a bivalent Hardjo/Pomona product. Four groups of
three calves were vaccinated at 4, 6, 10 and 18 weeks old, given a booster 4 weeks later and
challenged with serovar Hardjo by the intraperitoneal route 10-24 weeks after the second
45
vaccination. A control group of seven sero-negative calves from unvaccinated dams were
similarly challenged at 20 weeks old. None of the vaccinates were found to be leptospiruric or
kidney positive as assessed by culture, while all controls were leptospiruric by 35 days after
challenge. The authors concluded that ‘calves as young as 4 weeks of age may be effectively
vaccinated against serovar Hardjo in the presence of circulating maternally-derived antibody’.
An additional finding was that the post-vaccination rise in MAT titre was inversely proportional
to the pre-vaccination titre.
However, when assessing this study as evidence of the effect of MDA on vaccination the
following points should be considered:
MAT titres in the calves vaccinated at 4 weeks old were relatively low (given that the
MAT antigen strain was identical to the strain contained in the vaccine), specifically 4,
32 and 64 in the individual calves
The route of infection was not a natural one
The very small numbers observed (three in each group)
An internal report (Ankenbauer-Perkins, 2000) also considered the role of maternal antibody in
vaccine efficacy. Three groups of 10 calves from vaccinated dams were involved, with two
groups vaccinated with a bi-or tri-valent preparation (Hardjobovis, Pomona +/- Copenhageni) at
three to five weeks of age. Vaccinated calves were given a booster four weeks later, while a
third group was maintained as unvaccinated controls. The calves were selected for the study
based on high serum IgG concentrations (>1000mg/dL) at 4-10 days old, as a measure of
successful maternal antibody transfer. Challenge with serovar Hardjobovis was by the intranasal
and conjunctival route 12 weeks after the second vaccination, with 40% of each group found to
be leptospiruric by urine culture. The authors concluded that ‘the vaccination of three to five
week-old dairy heifers provided insufficient immunity against subsequent challenge.’
Again there are key points to consider:
The challenge model had limited success, with a 40% infection rate in controls
The calves were specifically selected for high MDA and thus represent calves with
sufficient colostrum intake which may be up to 50% of the newborn calves in a dairy
farm (Wesselink et al., 1999).
The outcome of this challenge experiment may be explained by MDA preventing
shedding in vaccinated and control calves equally, and that vaccine interfered with
MDA. In a trial with 40% shedders in two groups of 10 however, this explanation cannot
be differentiated from chance.
These two studies, with their conflicting outcomes, do not provide sufficient evidence on which
to base conclusions on the effect of MDA on vaccine efficacy. Such evidence would best be
obtained by longitudinal field studies, in naturally infected herds, to examine more closely the
interplay between the timing of first challenge, loss of maternally-derived protection and
response to vaccination in young calves.
According to Hellstrom (1978), soil moisture rather than rainfall per se was a strong determinant
for the rate at which new infection occurred. Leptospira survived 6 weeks in acidic soil (pH=5.5)
under simulated Manawatu winter conditions. New infections were regarded to be entirely due
to contact with other cattle on pasture, independent of the presence of infected wildlife.
The titre decay after infection was described by Adler et al. (1982) through experimental
inoculation of 8 month old susceptible heifers. Antibodies determined by IgM-Elisa, IgG-ELISA,
46
and MAT (measuring both IgM and IgG) started at zero, peaked about 7-10 days, held level until
about 28 days, and were negative again by 90-100 days after inoculation.
10.7 Duration of immunity
The immunity elicited by leptospiral vaccines has been shown in a number of studies to persist
for up to 13 months in cattle (Table 9.2). Duration of immunity has been demonstrated directly
by studying resistance to infection following experimental (McColl and Palit, 1994; Ellis et al.,
2000) or natural challenge with Hardjo strains (Marshall et al., 1979b; Flint and Liardet, 1980;
Mackintosh et al., 1980; Hancock et al., 1984), or indirectly by methods such as hamster passive
protection (Virbac tech review6). Although MAT titres to Pomona and Hardjo are often reported
in longitudinal studies of vaccine efficacy, with MAT titres in cattle shown to wane by 6 months
post-vaccination (Mackintosh et al., 1980), the relevance of titre persistence as a measure of
protection against challenge is questionable.
Indeed, the OIE (2008) recommends ‘Duration of immunity should not be estimated based on
the duration of MAT titres in vaccinated animals as protection against clinical disease may be
present with very low titres.’
Mackintosh et al. (1980), for example, demonstrated protection against urinary shedding in the
face of natural challenge with Hardjo at 56 weeks post-vaccination, when the animals were
sero-negative. Similarly, Zuerner et al. (2011) demonstrated that young cattle (n=15)
experimentally challenged with Hardjo by the conjunctival route 12 months after vaccination,
when MAT titres were almost zero, were protected against urinary shedding of live leptospires,
as measured by culture, while 7/7 controls were urine culture positive. The vaccinated group
had a background MAT mean serum titre of 1:100 at the time of challenge, compared to a peak
of 500 at four weeks post-vaccination.
Table 9.2: Evidence for duration of vaccine induced immunity, by challenge type, serovar, age at first
vaccination, and source.
Challenge
Serovar(s)
Age at first vaccination
Duration
Reference
of protection*
Experimental
Hardjo
4-5 months
48 weeks
(McColl and Palit, 1994)
Experimental
Hardjo
BW≥300 kg
12 months
(Ellis et al., 2000)
Natural
Hardjo
6-12 months
12 months
(Flint and Liardet, 1980)
Natural
Hardjo
3-4 months
7 months
(Marshall et al., 1979b)
Natural
Hardjo
10 months
56 weeks
(Mackintosh et al., 1980)
Natural
Hardjo
9-10 months
55 weeks
(Hancock et al., 1984)
Experimental
Hardjo
10 months
12 months
(Zuerner et al., 2011)
Experimental
Hardjo,
6 months
26 and 52
(Hamel, 1997)
Pomona,
weeks
Copenh.
*Number of weeks after vaccination that challenge occurred.
6
http://www.virbac.co.nz
47
10.8 Conclusions on vaccine efficacy to prevent shedding
Conflicting evidence for the effect of MDA precludes robust conclusion about its influence on
vaccine efficacy, and therefore the optimum timing of first vaccination. Titres of vaccineinduced MDA measured by MAT and possibly the extent of interference with calf-vaccination,
may depend on the timing of dam vaccination prior to calving. It is therefore suggested that, in a
low challenge environment including where whole herd vaccination is practised, MDA
sufficiently high to interfere with vaccine may not be expected (at least in many animals) as long
as dams had not been vaccinated shortly before calving. However, the high challenge
environment currently present in NZ for sheep, deer and beef cattle, some interference
between vaccines and MDA may exist if vaccination is commenced at a young age. The
Ankenbauer-Perkins (2000) trial suggests that such interference can reduce vaccine efficacy.
Therefore, early vaccination (2-6 weeks) of such species may only be advisable when a spot test
of 1month old calves suggests that measurable antibody is low or absent. If it is present, an
early course of vaccination may have to be boostered by an additional inoculation at 6 months
of age. Duration of immunity against Hardjo challenge has been shown to last up to 13 months.
11 Required information (future research)
The literature review of aspects involved in potentially modifying vaccine efficacy has revealed
that almost all studies were based on small numbers and were carried out under controlled
conditions often with an extremely high challenge dose. Moreover, it was difficult if not
impossible to compare studies investigating vaccination at different ages, with different
Leptospira antigens, with different periods between vaccination and challenge, different
challenge routes and with varying follow-up periods and measurements of efficacy.
This review found the crucial issue of optimal first vaccination age could not be resolved from
reviewing the literature to date. We believe that the review was exhaustive in terms of the
volume of published and accessible material, especially as several unpublished technical reports
were included that would be impossible to access when tracing from publicly accessible
databases. Such reports were kindly made available by commercial vaccine producers.
The review therefore identifies the following as research areas to address deficiencies and
shortcomings in present knowledge of leptospirosis in livestock, with relevance to vaccination.
Vaccine efficacy and age for starting vaccination programmes: There is a pressing need
for large scale field trials of vaccine efficacy in dairy herds, comparing vaccinated with
unvaccinated cows in conjunction with vaccinating calves at various ages (1, 3, 6
months) in endemic herds and flocks. This would provide more definitive evidence on
the effect of MDA, which is of critical importance to determination of optimum start
times for vaccination programmes;
Human studies: As extensive investigations at abattoirs have provided important
insights on potential human exposure, it is recommended that similar sero-prevalence
studies in humans be conducted among veterinarians, farmers and other people who
have frequent contact with animals (AITs, shearers, livestock truck drivers etc.). This
would contribute further to the rationale for decisions surrounding vaccination;
Duration of immunity: For such studies, a sufficiently long follow-up period (e.g. 24-36
months) should be used to demonstrate the duration of immunity. No information is
currently available about shedding (protection) beyond 56 weeks post vaccination. This
is of interest for aligning the timing of vaccination of calves to that of adults: when
calves have completed their course of vaccination at 4-6 months of age (Jan-Mar), it
would be desirable if seasonal herd managers were able to vaccinate the same animals
48
as replacement heifers 15 (rather than 3 or 12) months later at the same time as the
adult herd.
Shedding in vaccinated dairy herds: New results showing shedding in dairy herds
should be followed up by testing cows serologically and again by PCR of urine to identify
serovars associated with shedding, and to corroborate the preliminary findings of
Parramore et al., 2011 (unpublished). A crucial question is whether PCR positive urine is
infectious, i.e. containing live Leptospira at a sufficiently high dose;
Serovars in livestock. Livestock need to be screened to confirm which serovars are
present in livestock populations. For example, it is not known whether there has been
an incursion of new serovar’s since initial screening more than 30 years ago (e.g.
tentative data for Arborea), or the potential for livestock to have become a spill-over
host for Ballum, which could potentially explain recent human cases with that serovar.
This could have additional implications for the serovars incorporated in livestock
vaccines specific to the NZ environment.
Wildlife: Little is known about the quantitative distribution of serovars in wildlife (feral
pig, possum, rabbit, hedgehog, feral deer), in back-yard pigs and in rodents. Therefore,
cross-sectional trapping studies should be implemented. This should be combined with
use of recently developed molecular strain typing methods for investigation of between
species (domestic and wildlife) transmission.
Ecology: The distribution of Leptospira serovars in the environment can now be studied
as new, semi-quantitative real time PCR tests are available. The repeatability of these
PCRs for testing urine was confirmed. However, the RT-PCR has yet to be validated for
testing environmental samples (water, soil etc). Once RT-PCR was validated, samples
should be collected repeatedly in the four seasons from water and soils sources. This
would identify infection sources for humans and animals.
Effect of interventions: Together with the aforementioned information, a large body of
technical data will be available about individual aspects of Leptospira in the
environment and in various hosts and their interactions through transmission and
vaccination. The question remains as to what effect interventions, e.g. control
measures, have on the endemic equilibrium in human and animal hosts. Mathematical
modelling can be used to simulate such interventions. For example, vaccination of cattle
may/may not be sufficient to reduce transmission in sheep, and thereby indirectly
decrease human exposure. Modelling can provide insight into the extent that
vaccination may have to be carried out (vaccine take x proportion vaccinated) to
achieve a desirable impact. Consequently, cost and benefits may be evaluated to inform
decision makers at farm and industry levels about the return on investments.
Eradication of leptospirosis from New Zealand. The above research projects would
provide data for modelling the possibility of elimination of livestock-based serovars of
leptospirosis from New Zealand. This would have long-term implications for vaccine use
in future, and to developing strategies at a national level to manage the disease.
Vaccination in the face of an outbreak. There are no data on the serological response
to vaccination in the face of an outbreak (most likely to occur in sheep or deer).
Opportunistic studies should be conducted in outbreak situations by looking at
serovonversion in the face of an outbreak with comparison to known responses in the
non-emergency situation. This would help develop guidelines for management of an
outbreak.
49
12 Guideline for Best-Practice recommendations for vaccination
The review revealed that there currently exists a lack of sound, longitudinal data that can
conclusively demonstrate the effect of maternal antibodies, derived from natural exposure or
vaccination of dams, on the earliest age at which cattle or other species may effectively be
vaccinated against leptospirosis. This is a significant limitation to being able to recommend Best
Practice guidelines that fit all circumstances.
12.1 General principles for a vaccination programme: all species
NZVA’s Leptosure® programme provides general guidelines for vaccination detailing which stock
to vaccinate at what times of the year and how often. It also elaborates what additional
biosecurity measures are required to achieve a high level of herd immunity.7
Concepts and principles applied to decision-making about vaccination are described in detail in
deer (Wilson et al., 2009). There are no papers that discuss the principles of vaccination for
other species in New Zealand. Nevertheless, the principles described in the above paper are
applicable to other livestock species. There are recommendations for vaccination of dairy cattle
given by vaccine manufacturers.
The decision on whether or not to vaccinate is the prerogative of the farmer alone. Hence, the
farmer should be fully informed of leptospirosis, the risk factors for infection and disease, its
health and production effects, its epidemiology, public health implications, means of control
including vaccine and other measures, and economic implications. The veterinarian’s role is to
fully inform the farmer. This is to allow the farmer to evaluate the risk profile for the individual
farm and set the objective/s for the programme. An additional risk factor to consider is the
potential for litigation against farmers under Occupational Safety and Health legislation in the
event of workers or family contracting the disease.
The farmer must establish goals and objectives of the farm in relation to leptospirosis
vaccination, in terms of:
clinical disease (sick animals/mortalities),
subclinical disease (effect on reproduction and growth),
human safety (prevention of human sickness).
i.e. determine what is expected of the vaccine.
The risk needs to be evaluated that leptospirosis may pose to the achievement of those goals
and objectives. The veterinarian needs to identify the risk factors on the farm, including
environmental (within farm and external, e.g. waterways), management and stocking policies.
Note: while serological testing may be useful in demonstrating that leptospirosis infection is on
the property, it cannot be used to evaluate risk of cost-benefit of vaccination measured by
animal productivity outcomes. This is because the level of infection in a herd changes over a
period of time as environmental conditions become more or less favourable for the survival of
Leptospira. Further, determining whether there will be an “economic benefit” of vaccination is
impossible in advance since the incidence of infection cannot be reliably predicted, yet
vaccination needs to be administered prior to the risk.
Hence, the question of whether or not to vaccinate can only be based on evaluation of risk
rather than absolutes, and applied in relation to the risk-averseness of the farmer. The farmer
7
http://www.leptosure.co.nz/sites/default/files/domain18/Leptosure%20Green%20Farmer%20Booklet%202007.pdf
50
should be aware that other forms of reducing the risk attributable to leptospirosis are unlikely
to be as effective as vaccination.
The latest age at which the first course of vaccination should be completed depends on the level
of natural challenge. In high challenge situations or when farmers perceive that the risk of
human exposure is high, cattle, sheep and deer should be vaccinated early, e.g. at 1 month of
age. However, in low challenge situations, or when farmers perceive the human infection risk to
be low, or when vaccination has been applied according to label for a number of years, young
stock may be vaccinated later, e.g. at 6 months of age.
Start of seasonal
AB calving/
lambing
-10 0
Earliest
1st vacc
Latest
1st vacc
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
Days after the start of seasonal calving/lambing
Figure 12.1: Recommended time window (72-125 days) for the first sensitiser vaccination of
offspring replacements after the start of seasonal calving/lambing.
The recommended vaccination schedule is demonstrated in Figure 12.1: applying the first
vaccination 7 weeks after the start of calving (day 0) ensures all calves are well over the age of
one month when vaccinated for the first time. This is followed by a sensitisation approximately
4-6 weeks later (35 days in Fig. 12.1). In low risk situations (see below), the last opportunity for
calves of any age to have completed a course of vaccination should be at six months after the
actual start of calving. Note that the average age of calves at first vaccination is in the range of
49-115 days (7 – 16 weeks). In dairy herds, it may be advisable to vaccinate two calf-mobs at
subsequent times, (i) AI-bred replacements, and (ii) sire-mated calves for beef production.
The general ‘Best-Practice’ vaccination guideline differentiates two situations, (i) a ‘high risk’
vaccination, and (ii) a ‘low risk’ vaccination. We then briefly consider the use of vaccines in an
‘outbreak’ situation.
51
(i) ‘High risk’ vaccination
This situation applies when:
1. the farmer perceives that a high risk of human or animal exposure exists;
or
2. confirmed clinical cases have occurred and/or serological data from young
stock exist that objectively demonstrate a high level of challenge at an
early age.
The review suggests an estimated first vaccination age of approximately 6 weeks followed by a
booster at 3 months. In order to ensure maximum vaccine efficacy, animals should get a second
booster at 6 months of age followed by annual re-vaccination in 12 months intervals. One
vaccine producer recommends that the 6-months booster be another full course of 2vaccinations in 4-6 week interval. No conclusive data currently exist either in favour or against
this claim.
It is understood that deviations from this rule will be unavoidable. Due to variable times of
lambing/calving and practicalities on-farm, a recommended age of 6 weeks (3 months) will
effectively be a large range around this anticipated mean (or median) age.
(ii) ‘Low risk’ vaccination
In all other instances, it is recommended to complete the first course of two vaccinations when
animals are in the age range of 4-6 weeks up to 6 months of age followed by annual whole herd
vaccination (Figure 12.1).
(iii) Vaccination in an ‘outbreak’ situation
A leptospirosis outbreak is characterised by a sudden increase of clinical cases in a short period
of time. In this situation, it can be considered that all animals were exposed and most got
infected. Since leptospirosis vaccines have little effect in already infected animals, two steps are
recommended. Firstly, clinical cases and animals suspected to be in pre-clinical state should be
treated with antimicrobials. Secondly, the next offspring crop should be vaccinated early as
described for animals in a ‘high risk’ environment, then annually in subsequent years until
animals of all ages have been immunised.
52
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59
Annex I:
Note: these are guidelines only. Where these guidelines do not fit the circumstance on an
individual property, a first-principles approach to vaccination decisions needs to be adopted.
Best practice recommendations – DAIRY
Stock classes: breeding and replacement stock, growers kept at home or sold to beef
finishing farms. Vaccination of bobby calves is not required. Consider vaccinating calves
in two mobs: AI bred replacements and bull-mated tail-end for beef.
Figure 1: Timeline of farm management events in a representative New Zealand spring calving dairy herd with
calves leaving in June: vaccination times superimposed as red vertical bars (see text below for details)
‘High risk’ vaccination
First course of vaccination (2 injections within 4 weeks; 1 and 2 in Figure 1)
- 1st vaccination (sensitizer): at disbudding (10-14 weeks after start
of calving, Sep-Oct);
- 2nd vaccination: before transfer to runoff or replacement rearing
farm (14-18 weeks after start of calving, Oct-Nov).
- OPTIONAL (not backed up by scientific evidence): 3rd
vaccination 6 months after sensitizer (Mar-Apr);
- 1st annual booster: 5-7 months after 2nd vaccination when 10
months old (May), or as soon as convenient thereafter, to align
with adult stock.
Annual whole herd booster in May (3 in Figure 1)
- Lactating herd at dry-off (May)
- 1st calving cows: 32 months* of age (May)
[* this would be an interval of 14 months after the last booster whereas vaccine efficacy was only
evaluated up to 13 months, hence assuming one additional month of efficacy is deemed acceptable]
60
‘Low risk’ vaccination (herds with a history of regular vaccination)
Replacement calves:
reared at home
sent for grazing in December (4 months old)
sent for grazing in May/June (8-9 months old)
- 1st: at disbudding (10-18 weeks after start of calving, Sep-Nov);
- 2nd: before transfer to runoff or replacement rearing farm (14-22
weeks after start of calving, Oct-Dec);
- 1st annual booster: 5-7 months after 2nd vaccination when 10
months old (May), or as soon as convenient thereafter, to align
with adult stock.
Annual whole herd vaccination in May
- Lactating herd at dry-off
- Replacement heifers
Biosecurity measures
Assume that all bought in stock are unvaccinated. Vaccinate all young
replacement stock before they leave the property for rearing. Vaccinate all
purchased stock (cows, breeding bulls) at least 6 weeks before entering the
property. Where this is not possible or was not done, keep new stock on a
separate run-off that will not be grazed by the resident stock for at least 12 weeks
(quarantine).
For measures to protect exposure of humans, refer to the guidelines of NZVALeptosure.
61
Best practice recommendations – SHEEP
All stock classes: replacement hoggets/2T, breeding rams and mixed age ewes.
Figure 2: Timeline of farm management events in a representative New Zealand self-replacing commercial sheep
flock with high-risk vaccination times superimposed as red vertical bars (see text below for details)
‘High risk’ vaccination
First course of vaccination (2 injections within 4 weeks; 1 and 2 in Figure 2)
- 1st vaccination: at tailing (3-4 weeks old, Sep-Oct);
- 2nd vaccination: 4-6 weeks after 1st vaccination, e.g. at lamb shear (8-10
weeks old, Oct-Nov).
Booster at 6-months of age (3 in Figure 2)
- 3rd vaccination: at last ecto-parasite control (dipping) end of summer (Mar)
Annual whole flock vaccination in May (3 in Figure 2)
- At last ecto-parasite control (dipping) end of summer (Mar)
‘Low risk’ vaccination
First course of vaccination (2 injections within 4-6 weeks):
Replacement hoggets
- 1st vaccination: at weaning (2-3 months old, Dec-Jan)
- 2nd vaccination: 4-6 weeks later (Jan-Mar, 3-4 months old)
Annual whole flock vaccination in May
- At last ecto-parasite control (dipping) end of summer (Mar)
62
Biosecurity measures
Assume all purchased or transferred-in stock was unvaccinated. Vaccinate all
purchased replacement and breeding stock (hoggets, 2Ts, breeding rams) at least
6 weeks before entering the property. Where this is not possible or was not done,
keep new stock on a separate run-off that will not be grazed by the resident flock
for at least 12 weeks (quarantine).
For measures to protect exposure of humans, refer to the guidelines of NZVALeptosure.
63
Best practice recommendations – BEEF
All stock classes: calves for meat or replacement, heifers and mixed age cows.
Figure 3: Timeline of farm management events in a representative New Zealand beef herd with high-risk
vaccination times superimposed as red vertical bars (see text below for details)
‘High risk’ vaccination
First course of vaccination (2 injections within 4 weeks; 1 and 2 in Figure 3)
- 1st vaccination: at ear-marking (4-6 weeks old, Oct-Nov);
- 2nd vaccination: 4-6 weeks after 1st vaccination (10-12 weeks old, Nov-Jan).
Booster at 6-months of age
- 3rd vaccination: for example at weaning end of summer (Mar-Apr; 3 in
Figure 3)
Annual whole herd vaccination in July-August pre-calving (4 in Figure 3)
‘Low risk’ vaccination
First course of vaccination (2 injections within 4 weeks)
- 1st vaccination: at ear-marking (4-6 weeks old, Oct-Nov);
- 2nd vaccination: 4-6 weeks after 1st vaccination (10-12 weeks old, Nov-Jan).
Booster and annual whole herd vaccination in July-August pre-calving
Biosecurity measures
Assume all purchased or transferred-in stock was unvaccinated. Vaccinate all
purchased replacement and breeding stock (heifers, bulls, mixed age cows) at
least 6 weeks before entering the property. Where this is not possible or was not
done, keep new stock on a separate run-off that will not be grazed by the resident
flock for at least 12 weeks (quarantine).
For measures to protect exposure of humans, refer to the guidelines of NZVALeptosure.
64
Best practice recommendations – DEER
All stock classes: fawns for meat or replacement, rising 2-year old hinds, mixed age
hinds, and stags for breeding or for antler production.
Figure 4: Timeline of farm management events in a representative New Zealand deer herd with high-risk
vaccination times superimposed as red vertical bars (see text below for details)
‘High risk’ vaccination
First course of vaccination (2 injections within 4 weeks starting late
February/early March, Figure 4)
- 1st vaccination: 10-12 weeks old, late February/early March;
- 2nd vaccination: 4-6 weeks after 1st vaccination (14-16 weeks old, late
March/early April).
Booster at 9-11 months of age
- 3rd vaccination in late October at the time of whole herd booster vaccination
(Figure 4)
Annual whole herd vaccination in late October (Figure 4)
‘Low risk’ vaccination
Same as for high risk scenario.
Biosecurity measures
Assume all purchased or transferred-in stock was unvaccinated. Vaccinate all
purchased replacement and breeding stock (yearling hinds, stags, mixed age
hinds) at least 6 weeks before entering the property. Where this is not possible or
was not done, keep new stock on a separate run-off that will not be grazed by the
resident flock for at least 12 weeks (quarantine).
For measures to protect exposure of humans, refer to the guidelines of NZVALeptosure.
65
Annex II: List of vaccine efficacy studies where the outcome was
urine shedding
66
Challenge
(Dose-Route)
Natural
exposure to L.
hardjo
Vaccine
(Dose-Route)
Tasvax Lepto 2:
Bivalent
(L. hardjo-L.pomona)
2 doses, 1 month
apart.
Host, age at
vaccination
7 months
replacement
heifers
negative to
MAT (<1:32)
and no
leptospira
cultured
from urine.
Natural
exposure
Leptavoid-3
Polivalent (L. hardjo,
L. Pomona and L.
copenhageni)
Weaners in
farm with
history of
infection
Leptoferm-5:
Pentavalent
(Leptospira canicola,
L. grippotyphosa, L.
hardjo, L.
icterohaemorrhagiae
, and L. Pomona)
Intra-Muscular 1
dose or 2 doses 6
months apart
2 year old
cows and an
angus bull
negative to
MAT
(<1:40).
Bred 1-2
months
after last
vaccination
8
10 organisms
in 1ml o, and
4
10 organisms
in 1ml of urine
of shedding
cow by
conjunctival
instillation of L.
hardjo.
Exposed at 4-6
months of
gestation
Antibody status (MAT)
Control
43 controls
Week 24: 85%
were positive.
Control
Evidence of
infection
(seropositive)
in control
animals
Control:
5 Controls:
All positive at
least once
Shedding
Efficacy
(1–RR)
Urine
Week 18
DGM: 81%
Culture: 71%
Both: 68%
Week 22
DGM: 75%
Culture: 100%
Both: 78%
Reference
Vaccine
39 vaccinated
Week 6: all
positive to
both serovars.
Week 24: 95%
negative to L.
hardjo.
No L. pomona
seroconversio
n
Vaccine
Seroconverted
after
vaccination
Control
Week 18
DGM: 17/43
Culture: 15/43
Both: 24/43
(56%)
Week 22
DGM: 21/41
Culture: 10/41
Both: 24/41
(58%)
Control
38.4% positive to
DFM (n=252
samples)
Vaccine
Week 18
DGM: 3/39
Culture: 4/39
Both: 7/39 (18%)
Week 22
DGM: 5/39
Culture: 0/39
Both: 5/39 (13%)
Vaccine
24.6% positive to
DFM (n=292
samples)
44%, from
multivariable model
(AyaneguiAlcerreca,
2006)
Vaccine:
15 Vaccinated
cows:
7 single/8
double; no
single
vaccinated
had MAT titres
≥1:40.
Control:
Urine:
Culture: 5/5
culture
(FA): 5/5
Kidney
(histopathology)
:
Cow: 4/5
Calf: 4/4
Vaccine:
Urine
1 dose
Culture: 0/7
FA: 6/7
2 doses
Culture: 1/8
FA: 7/8
Kidney
(histopathology)
1 dose
Cow: 6/7
Calf: 6/7
2 doses
Cow: 6/8
Calf: 7/8
Urine
1 dose
Culture: 100%
FA: 14%
2 doses
Culture: 88%
FA: 13%
Kidney
1 dose
Cow: -7%
Calf: 14%
2 doses
Cow: 6%
Calf: 13%
(Bolin et al.,
1989a)
67
(Allen et al.,
1982)
7
10 organisms
of hardjo-bovis
in 1ml, 3 times
during week
26 after first
vaccination.
Also urine of a
known
shedder was
instilled the
conjuctival sac
on week 28
Two pentavalent
vaccines containing
hardjo-prajitno or
hardjo-bovis, 2 ml
intramuscular, one
or two doses, 3
weeks apart
18, 4-8
months old
steers
seronegativ
e to lepto
Group 1:
n=2; 1
vaccination
hardjoprajitno
Group 2:
n=4
2 doses
hardjoprajitno
Group 3:
n=4; 1 dose
hardjo-bovis
Group 4:
n=4; 2 doses
hardjo-bovis
Control:
No titres until
challenge
Vaccine:
All groups
generated
MAT titres
after
vaccination
68
Control:
Urine
Culture 3/4
positive
FA 4/4
Kidney
Culture: 3/4
FA: 4/4
DFM: 4/4
Histology: 4/4
Vaccine:
Urine
Group 1
Culture: 0/2
FA: 2/2
Group 2
Culture: 0/4
FA: 4/4
Group 3
Culture: 0/4
FA: 4/4
Group 4
Culture: 0/4
FA: 4/4
Kidney
Group 1
Culture: 0/2
FA: 2/2
DFM: 2/2
Histology: 2/2
Group 2
Culture: 0/4
FA: 3/4
DFM: 3/4
Histology: 2/4
Group 3
Culture: 0/4
FA: 4/4
DFM: 4/4
Histology: 2/4
Group 4
Culture: 0/4
FA: 4/4
DFM: 4/4
Histology: 4/4
Urine
Group 1
Culture: 100%
FA:
Group 2
Culture: 100%
FA: 0%
Group 3
Culture: 100%
FA: 0%
Group 4
Culture: 100%
FA: 0%
Kidney
Group 1
Culture: 100%
FA: 0%
DFM: 0%
Histology: 0%
Group 2
Culture: 100%
FA: 25%
DFM: 25%
Histology: 50%
Group 3
Culture: 100%
FA: 0%
DFM: 0%
Histology: 50%
Group 4
Culture: 100%
FA: 0%
DFM: 0%
Histology: 0%
(Bolin et al.,
1989b)
5
10
organisnms in
1 ml by
conjuctival
instillation on
3 consecutive
days. 7, 11 or
15 weeks post
vaccination
Two monovalent
vaccines containing
8
10 organisms in 2ml
9
or 10 organisms in 4
ml of hardjo-bovis
intramuscular 4
weeks apart
19, 4-6
month old
heifers and
1 4 month
old steer
seronegativ
e to lepto
Group 1:
n=9 2 doses
of low-dose
Group 2:
n=8 2 doses
of high-dose
Control
Seronegative
until
challenge,
seroconvertio
n after
challenge
Vaccine
Seroconverted
after
vaccination
69
Control
Urine
Culture: 2/2
FA: 2/2
Kidney
Culture: 2/2
FA: 2/2
Histology: 2/2
Vaccine
Urine
Group 1, 7 weeks
Culture: 1/3
FA: 3/3
Group 1, 11 weeks
Culture: 1/3
FA: 3/3
Group 1, 15 weeks
Culture: 2/3
FA: 3/3
Group 2, 7 weeks
Culture: 2/3
FA: 3/3
Group 2, 11 weeks
Culture: 1/3
FA: 3/3
Group 2, 15 weeks
Culture: 1/3
FA: 3/3
Kidney
Group 1, 7 weeks
Culture: 3/3
FA: 3/3
Histology: 3/3
Group 1, 11 weeks
Culture: 1/3
FA: 1/3
Histology: 3/3
Group 1, 15 weeks
Culture: 1/3
FA: 3/3
Histology: 3/3
Group 2, 7 weeks
Culture: 1/3
Urine
Group 1, 7 weeks
Culture: 67%
FA: 0%
Group 1, 11 weeks
Culture: 67%
FA: 0%
Group 1, 15 weeks
Culture: 2/3
FA: 0%
Group 2, 7 weeks
Culture: 33%
FA: 0%
Group 2, 11 weeks
Culture: 67%
FA: 0%
Group 2, 15 weeks
Culture: 67%
FA: 0%
Kidney
Group 1, 7 weeks
Culture: 0%
FA: 0%
Histology: 0%
Group 1, 11 weeks
Culture: 67%
FA: 67%
Histology: 0%
Group 1, 15 weeks
Culture: 67%
FA: 0%
Histology: 0%
Group 2, 7 weeks
Culture: 67%
FA: 0%
(Bolin et al.,
1991)
4 in each
6
group 1×10
organisms in
1ml by
conjunctival
instillation (CI)
of L. hardjo
Rest 4 in each
9
group: 5×10
intraperitoneal
inoculation (IP)
16 weeks after
second
vaccination
Spirovac:
Monovalent (L.
hardjo)
2 doses, 4 weeks
apart. 2ml
subcutaneously.
Reference vaccine:
Prepared according
to USDA (APHIS). 2
doses, 4 weeks
apart. 2ml intramuscular.
8-12 months
old heifers,
negative to
MAT (<12.5)
Control
8 Controls:
Negative at
challenge, all
positive after
exposure.
Vaccine
8 reference
vaccine:
6/8 negative
at challenge
(16 weeks
after second
dose)
8 commercial
vaccine:
None MAT
negative at
challenge
Control
Urine
IP: 2/4
CI: 4/4
Total: 6/8
Kidney
IP: 4/4
CI: 4/4
Total: 8/8
Natural
exposure
Calf trial:
introduction of
4 animals
shedding
Leptavoid:
Bivalent (L. hardjo
and L. pomona), 2
doses 4-6 weeks
apart
subcutaneously
Calf trial: 34 months
old
Heifer trial:
10 months
old
Control
Calf trial
10 controls:
All
seropositive
37-41 days
Vaccine
Calf trial
9 vaccinated:
6/9 with MAT
titres after
second dose.
Control
Calf trial:
Culture: 6/10
Heifer trial:
Culture: 9/10
70
FA: 3/3
Histology: 2/3
Group 2, 11 weeks
Culture: 2/3
FA: 2/3
Histology: 1/3
Group 2, 15 weeks
Culture: 1/3
FA: 1/3
Histology: 2/3
Vaccine
Reference vaccine
Urine
IP: 4/4
CI: 4/4
Total: 8/8
Kidney
IP: 3/4
CI: 3/4
Total: 6/8
Commercial vaccine
Urine
IP: 0/4
CI: 0/4
Total: 0/8
Kidney
IP: 0/4
CI: 0/4
Total: 0/8
Vaccine
Calf trial:
Culture : 0/9
Heifer trial:
Culture : 2/8
Histology: 33%
Group 2, 11 weeks
Culture: 33%
FA: 33%
Histology: 67%
Group 2, 15 weeks
Culture: 67%
FA: 67%
Histology: 33%
Reference vaccine:
Urine
IP: -100%
CI: 0%
Kidney
IP: 25%
CI: 25%
-33%
Commercial vaccine
Urine
IP: 100%
CI: 100%
Kidney
IP: 100%
CI: 100%
92%
(Bolin and
Alt, 2001)
Calf trial: 91%
(Broughton
et al., 1984)
Heifer trial: 72%
leptospiras 2
weeks after
vaccination
Heifer trial: 4
infected
animals at
time of first
vaccination
retained
Leptavoid-H:
Monovalent (L.
hardjo)
after first dose
Heifer trial:
10 controls:
All
seropositive 8
weeks after
first
vaccination
Artificial
challenge:
8
1×10
organisms by
intraperinoteal
inoculation of
L. hardjo 14
days after
second dose
Natural
challenge
9 farms with
history of
leptospiral
infection
Prepared vaccine:
Trivalent (L. hardjo,
L. pomona, and L.
copenhageni)
2 doses 21 days
apart
subcutaneously at 46 months old.
Artificial
challenge:
4-6 months
old heifers
with no
MAT titers
to L. hardjo,
L. pomona,
and L.
copenhageni
Natural
challenge
6-12 months
old heifers
Control
Artificial
challenge:
10 heifers,
7/10
seroconverted
after
challenge.
Natural
challenge
3 properties
natural
challenge
occurred
Diluted urine
(1:2) of known
L. pomona
shedders
instilled into
eyes and
nostrils, and
Leptogen (Vaccine 1)
Monovalent
(L. pomona)
Commercial (Vaccine
2)
Monovalent
(L. pomona)
36 heifers 68 months
old (group
1)
18 calves 12 months
old
Control
Group 1: No
titres prechallenge
Group 2: No
titres prechallenge
2/9
seroconverted
38-41 weeks
after first
dose.
Heifer trial:
8 vaccinated:
All with MAT
titres after
second dose.
No titres at 21
weeks.
Vaccine
Artificial
challenge:
10 heifers, all
seroconverted
against the 3
serovars after
vaccination.
Natural
challenge
60/66
seroconverted
to hardjo and
pomona after
vaccination
Vaccine
Group 1:
vaccine 1: 5/5
titres prechallenge.
vaccine 2: 4/5
titres pre-
71
Control
Artificial
challenge:
Urine: 7/10
positive to
culture and
direct
examination
Natural
challenge
Herd 3: 6/14
shed leptospira
Herd 7: 2/8 shed
leptospira
Herd 9: 6/10
shed leptospira
Control
Group 1: 4/5
shed leptospiras
detected by
darkfield
microscopy 3/5
only by DFM
Vaccine
Artificial challenge:
Urine: 0/10 shed
leptospiras
Natural challenge
Herd 3: 1/9 shed
leptospira
Herd 7: 0/8 shed
leptospira
Herd 9: 1/10 shed
leptospira
Artificial challenge
93%
Natural challenge
Overall: 85%
(Flint and
Liardet,
1980)
Vaccine
Group 1:
Vaccine 1: 0/5
shedding
Vaccine 2: 0/5
shedding
Vaccine 3: 0/2
Group 1
Vaccine 1: 100%
Vaccine 2: 100%
Vaccine 3: 100%
Group 2
Vaccine 1: 60%
Vaccine 2: 16%
(Gillespie
and Kenzy,
1958a)
contaminated
drinking water
6.5-8.5 months
after
vaccination
Experimental
(Vaccine 3)
Monovalent
(L. pomona)
Single dose
subcutaneously
challenge
61/2 months
after
vaccination
(group 2) or
8 months
after
vaccination
(group 3)
Group 3
No titres prechallenge
Diluted urine
(1:5) of known
L. pomona
shedders
instilled into
eyes and
nostrils, and
contaminated
drinking water
13-20 months
after
vaccination
Leptogen (Vaccine 1)
Monovalent
(L. pomona)
Commercial (Vaccine
2)
Monovalent
(L. pomona)
Experimental
(Vaccine 3)
Monovalent
(L. pomona)
Single dose
subcutaneously
Commercially
prepared
Bivalent (L. hardjo
and L. pomona)
35 cows, 24
vaccinated
when 6-8
months old
exposed at
13-15
(group 4) or
18-20(group
5) months
after
vaccination
78 heifers,
37
previously
vaccinated
Natural
challenge
Group 2: 5/6
shed leptospires.
Group 3: 3/3
shed leptospires
shedding.
Group 2
Vaccine 1: 1/3 shed
leptospires
Vaccine 2: 4/4 shed
leptospires
Group 3:
Vaccine 1: 2/3 shed
leptospires
Vaccine 2: 2/3 shed
leptospires
Group 3:
Vaccine 1: 33%
Vaccine 2: 33%
Control
Group 4
0/5 titres
before
exposure
Group 5
0/6 titres
before
exposure
challenge.
vaccine 3: 2/2
titres prechallenge.
Group 2:
vaccine 1: 1/4
titres prechallenge
vaccine 2: 0/5
titres prechallenge.
Group 3:
vaccine 1: 0/4
titres prechallenge
vaccine 2: 1/4
titres prechallenge.
Vaccine
Group 4
6/12 titres
before
exposure
Group 5
6/12 titres
before
exposure
Control
Group 4
4/5 shed
leptospires
Group 5
5/6 shed
leptospires
Group 4
Vaccine 1: 6%
Vaccine 2: 16%
Vaccine 3: 100%
Group 5
Vaccine 1: 100%
Vaccine 2: 60%
(Gillespie
and Kenzy,
1958b)
Control
22 C2:
unvaccinated
1:256 at
Vaccine:
18 V1: booster
after 60 weeks
of calfhood
Control
Controls 1 (C1):
First vaccination
at 22-23 mo
Vaccine
Group 4
Vaccine 1: 3/4 shed
leptospires
Vaccine 2: 2/3 shed
leptospires
Vaccine 3: 0/1 shed
leptospires
Group 5
Vaccine 1: 0/1 shed
leptospires
Vaccine 2: 1/3 shed
leptospires
Vaccine
Vaccine 1 (V1):
55 weeks: 1/18
77 weeks: 3/13
55 weeks:
V1 v/s C1
88%
V1 vs C2
(Hancock et
al., 1984)
72
Natural
transmission
from 4
infected
heifers
Natural
transmission
from 4
infected
animals
8
2×10 bovine L.
hardjo
Intraperitoneal
and
intramuscular
6 weeks after
subcutaneously
and
challenged
and 41 nonvaccinated
challenged
55weeks
55 weeks: 9/19
77 weeks: 4/15
positive to either
dark ground
microscopy or
culture
Control 2 (C2):
Unvaccinated
55 weeks: 15/22
77 weeks: 4/9
positive to either
dark ground
microscopy or
culture
positive to either
dark ground
microscopy or
culture
Vaccine 2 (V2):
55 weeks: 0/19
77 weeks: 1/12
positive to either
dark ground
microscopy or
culture
92%
V2 v/s C1
100%
V2 v/s C2
100%
77 weeks:
V1 v/s C1
14%
V1 vs C2
48%
V2 v/s C1
69%
V2 v/s C2
81%
Control
10/10
seronverted 4
weeks after
start of
infection
Control
10/10
seroconverted
32-35 weeks
after
vaccination
vaccination
No titres at 55
weeks
19 V2: not
revaccinated
1:2 at 55
weeks
19 C1: First
injection at
22-23 months
old and
booster 6
weeks later
1:1024 at 55
weeks
Vaccine
8/8
seroconverted
to both L.
hardjo and L.
pomona
Vaccine
2/9
seroconverted
32-35 weeks
after
vaccination
Commercially
prepared vaccine
Bivalent (L. hardjo
and L. pomona)
2 doses 4 weeks
apart
Commercially
prepared vaccine
(same as
mackintosh, 1980)
Bivalent (L. hardjo
and L. pomona)
2 doses, 6 weeks
apart
prepared vaccine
Bivalent (L. hardjo
and L. pomona)
2 doses 1 month
apart
18, 10months old
heifers
seronegativ
e at first
vaccination
19, 3-4
months old
calves
serologically
negative
(<1/24)
Control
9/10 shedding
leptospira
positive by
culture
Vaccine
2/8 shedding
leptospira positive
by culture
72%
(Mackintos
h et al.,
1980)
Control
6/10 shed
leptospire
positive by
culture
Vaccine
0/9 shed leptospire
positive by culture
91%
(Marshall et
al., 1979b)
19, 7-9
months old
ewes
serologically
negative
Control
Seronegative
at challenge,
all
seroconverted
after
Vaccine
6/9
seroconverted
after
vaccination.
All positive
Control
10/10 isolated
from kidney
Vaccine
2/9 isolated from
kidney
78%
(Marshall et
al., 1979a)
73
second
vaccination
9
2×10 L.
pomona
organisms
subcutaneousl
y 19 days after
second dose of
vaccine
8
10 L. pomona
organisms/ml,
5ml
subcutaneousl
y
10 ml
containing
5
1×10
leptospires/ml
intraperitoneal 8
months after
vaccination
2×10
9
challenge
after challenge
Leptavoid
Bivalent (L. hardjo
and L. pomona)
2 doses 1 month
apart
22, 6
months old
serologically
negative to
L. pomona
<1:24
Control
11/11
seroconverted
5 days after
challenge
Vaccine
11/11
seroconverted
at second dose
of vaccine
Control
8/11 isolated
from urine
(culture)
Vaccine
0/11 isolated from
urine (culture)
100%
(Marshall et
al., 1982)
Prepared vaccine
Monovalent (L.
pomona)
1 or doses to
pregnant cows in the
last 2 months of
pregnancy. Calves
were allowed to
suckle calostrum for
at least 24 hours
Exp 1:
10 days old
calves were
challenged
Exp 2:
Challenge at
4 weeks of
age
Control
Exp 1: 3/10
had titres
comparative
low at
challenge
Exp 2: 2/10
had titres at
challenge
Vaccine
Exp 1: All had
titres at
challenge
Exp 2: 12/15
had titres at
challenge
Vaccine
Exp 1: 0/11 either
haemoglobinuria
and death or
leptospiruria in
dark-ground
microscopy
Exp 2: 1/15 either
haemoglobinuria
and death or
leptospiruria in
dark-ground
microscopy
Exp 1: 100%
Exp 2: 93%
(McDonald
and Rudge,
1957)
Commercial vaccine
Bivalent (L.
Icterohaemorrhagiae
and L. canicola)
1 dose or 2 doses 60
days apart
42, 5-6
months old
calves,
seronegativ
e
Control
Higher titres
than
vaccinated
calves after
exposure
Vaccine
Similar pattern
of titres after
exposure, but
lower titres.
Control
Exp1: 8/10
either
haemoglobinuria
and death or
leptospiruria in
dark-ground
microscopy
Exp 2: 9/10
either
haemoglobinuria
and death or
leptospiruria in
dark-ground
microscopy
Control
6/6 shed
leptospira,
positive by
culture to both
serovars
Vaccine
1 dose: 7/7 shed L.
canicola, 7/8 shed L.
Icterohaemorrhagia
e
1 dose:
Canicola: 0%;
Icterohaemorrhagia
e 13%
2 doses:
Canicola: 0%
Icterohaemorrhagia
e 14%
(Morsi et
al., 1973)
21 days: 100%
(Palit et al.,
Experimental vaccine
Seronegativ
Control
Vaccine
Control
74
2 doses: 8/8 shed L.
Canicola, 6/7 shed L.
Icterohaemorrhagia
e
Vaccine
organisms of L.
hardjo /ml
1 ml intraperitoneal
At 30-32
weeks of age.
6
10 L. hardjo
strain 203/ml
at 105, 106,
and 107 days
since first
vaccination by
conjuctival
instillation
Bivalent (L. hardjo
and L. pomona)
2 doses, 4 weeks
apart
Modified-live virus
Virus (BRD, BVD,
parainfluenza 3,
Bovine respiratory
syncytial virus)
Bacteria (C. fetus, L.
canicola, L.
grippothyphosa, L.
hardjo, L.
icterohaemorrhagiae
, and L. Pomona) or
H. somnus
e cows in
first
pregnancy
were
vaccinated
and calves
challenged.
Calves had
calostral
titres before
vaccination.
Group 1
Vaccinated
at 4 weeks
Group 2
Vaccinated
at 6 weeks
Group 3
Vaccinated
at 10 weeks
Group 4
Vaccinated
at 18 weeks.
55, 6
months old
heifers
seronegativ
e to lepto.
Group 1:
modifiedlive virus
plus
bacterin
Group 2:
killed virus
7
unvaccinated
calves from
unvaccinated
dams.
All
seroconverted
post
vaccination,
the rise of
antibodies was
comparative
lower than the
one in control
calves.
21 days after
challenge
5/7 (71%)
35 days after
challenge 7/7
(100%)
By dark field
microscopy
Group 1
0/3
Group 2
0/3
Group 3
0/3
Group 4
0/3
Total: 0/12 by dark
field microscopy
35 days: 100%
1991)
Control
Seronegative
until
challenge.
Only
seroconverted
to L. hardjo
(11/11)
Vaccine
Transient
titres in 40%
to 70% of the
vaccinates
heifers
For L. hardjo
<24% reacted
to vaccine.
Remained
seronegative
after challenge
Control
Urine: 11/11
culture positive
Kidney: 10/11
culture positive
Vaccine
Urine:
Group 1: 0/21
culture positive
Group 2: 0/21
culture positive
Kidney:
Group 1: 0/21
culture positive
Group 2: 0/21
culture positive
100%
(Rinehart et
al., 2012)
75
8
38×10 L.
pomona
organisms,
intramuscular
8
65×10 L.
pomona
organisms,
intramuscular
10 ml, 47
weeks after
second
vaccination
killed virus
same plus
H. somnus
2 doses 21 days
apart
2 comercial vaccines.
Monovalent (L.
pomona)
2 doses, 4 weeks
apart for vaccine A,
and 1 dose of
vaccine B.
plus
bacterin
Control:
modifiedlive virus
4 vaccinated
and
challenge
heifer calves
treated
before
vaccination
3 vaccines:
Vaccine A,
commercial,
subcutaneously
Vaccine B,
experimental,
subcutaneously
Vaccine C,
experimental,
intraperitoneally
16, 9
months old
heifer
calves,
seronegativ
e to
leptospira
3 vaccines 2 doses,
11 weeks apart
8
15×10 L.
Pomona,
subcutaeously
Experimental vaccine
Monovalent (L.
pomona)
subcutaneously
19 young
steers,
seronegativ
e to
leptospira
Control
No titres
before
challenge
Control
All
seronegative
before
challenge.
After
challenge
titres reached
high levels and
comparative
higher than
the one in
vaccinated
groups
Control
No
information
about titres
Vaccine
Vaccine A
All
seroconverted
after second
dose
Vaccine B
None
seroconverted
after
vaccination
Vaccine
Vaccine C
produced
higher titres
Control
1/2 positive
urine to direct
dark-ground
microscopy
Vaccine
Vaccine A
0/2 positive urine to
direct dark-ground
microscopy
Vaccine B
2/2 positive urine to
direct dark-ground
microscopy
Vaccine A:
100%
Vaccine B
50%
(Ris, 1977)
Control
4/4 leptospira
isolated from
urine
Vaccine
0/12 leptospira
isolated from urine
100%
(Ris and
Hamel,
1979)
Vaccine
Seroconverted
after
vaccination
Control
4/6 shed
leptospira
Vaccine
0/13 shed leptospira
100%
(Stalheim,
1968)
76
Group 1
48 billons in
16cc of L.
pomona
Group 2
49.2 billons in
6cc of L.
Grippotyphosa
Group 3
(Failed)
54 billons in 30
cc of L. hardjo
All
intravenously
Natural
exposure 2
months after
second dose
by mixing with
not treated
cohort
7
1×10
organisms of L.
hardjo, by
conjunctival
instillation
Leptomune-GHP
polyvalent (L. hardjo,
L. pomona, and L.
grippotyphosa)
2 doses, 4 weeks
apart
subcutaneously or
intramuscular
12
seronegativ
e cattle
4 in each
group,
including
control
Control
Seroconverted
post challenge
Vaccine
Seroconverted
after
vaccination.
Control
Group 1:
3/5
Group 2:
3/5
Group 3:
0/5
6/10 isolated
from renal tissue
Vaccine
Group 1:
0/3
Group 2:
0/4
Group 3:
0/4
0/7 isolated from
renal tissue
Group 1:
100%
Group 2:
100%
Group 3:
0%
Total: 88%
(Strother,
1974)
Leptavoid-2
Bivalent (L. hardjo, L.
pomona)
2 doses, 28 days
apart
subcutaneously
230 female
and 205
male, 3
months old
deer from 5
farms
Control
Some
seroconverted
after exposure
ranging from
0%-78% in
different
farms for L.
hardjo. None
seroconverted
to L. pomona
Control
controls treated
8/34
controls not
treated
20/38
In 2 farms,
diagnosed by
PCR and/or
culture
Vaccine
0/30 in same two
farms diagnosed by
PCR and culture
100%
(Subharat
et al., 2012)
Spirovac
Monovalent (L.
hardjo)
Experimental
Monovalent (L.
23, 10
months old
steers
seronegativ
e to
Control
Seronegative
until
challenge.
Higher
Vaccine
20 days after
booster, some
seroconverted
to L. hardjo
ranging from
39%-73% in
different
farms.
Some also
seroconverted
to L. pomona
ranging from
78%-100% in
different
farms
Vaccine
Seroconverted
after
vaccination ,
and again
Control
7/7 positive by
PCR, FA or
culture
7/7 only by
Vaccine
Vaccine 1:
6/8 positive by PCR
or FA,
0/8 only by culture
Vaccine 1
PCR or FA: 25%
Culture: 100%
Vaccine 2
PCR or FA: 0%
(Zuerner et
al., 2011)
77
1 year after
second dose
hardjo)
2 doses, 4 weeks
apart
leptospira
response after
challenge
compared to
vaccinated
groups
after
challenge,
although titres
were lower
than the ones
in the control
group
78
culture
Vaccine 2:
7/7 positive by PCR
or FA,
0/7 only by culture
Culture: 100%
Annex III: List of vaccines commercially available for cattle, sheep and deer in New Zealand (July 2012)
Trade Name
Leptavoid 2
Leptavoid 3
Cattlevax
Leptoshield
Species
Cattle,
Sheep,
Deer,
Pigs.
Serovars
Hardjo, and
Pomona
Use
For active immunisation against leptospira. Vaccination of healthy cattle will prevent
urinary shedding for 12 months. Vaccination will not alter the shedding status of
infected animals.
Primary: Two 2ml doses SC 4 to 6 weeks apart
Calves: Maternal antibodies may interfere with the response to vaccination if
administered before 6 months of age. If primary vaccination is completed before 6
months of age, a booster is required once they reach 6 months of age.
Booster: 2ml dose SC within 12 month after PV, and annually thereafter, ideally prior
to parturition.
Cattle, Deer
Hardjo,
For active immunisation against leptospira. Vaccination of healthy cattle will prevent
Pomona, and
urinary shedding for 12 months. Vaccination will not alter the shedding status of
Copenhageni
infected animals.
Primary: Two 2ml doses SC 4 to 6 weeks apart
Calves: If primary vaccination is completed before 6 months of age, a booster is
required once they reach 6 months of age
Booster: 2ml dose SC within 12 month after PV, and annually thereafter, ideally prior
to parturition
Cattle
Hardjo, Pomona and For active immunisation against leptospirosis. Vaccination of cattle before infection
Clostridiums
will prevent urinary shedding of leptospira. Vaccination will not alter the shedding
status of infected animals
Primary: Two 4ml doses SC 4 to 6 weeks apart. Vaccination should be completed 2
weeks prior to the period of risk.
Calves: Maternal antibodies may interfere with the response to vaccination if
administered before 6 month of age. Calves in high risk areas may be vaccinated form
4 weeks of age. A booster is essential at 6 months of age
Booster: Annually; or every 6 months in areas where clostridial disease challenge is
high
Cattle, Sheep, Hardjo, and
For the prevention of leptospirosis in cattle, sheep and goats. And as an aid in the
Goats, Deer
Pomona
control of leptospirosis in deer.
79
Registrant
MSD
MSD
MSD
Pfizer
Vaxall Lepto
HP
Vaccine for
Cattle
Cattle
Ultravac 7 in
1
Cattle
Leptoshield 3
Cattle
For the prevention of urinary shedding of leptospira in healthy cattle and protection
against reproductive losses.
Primary: Two 2ml doses SC 4 to 6 weeks apart, before season of high risk (autumn to
early summer).
Calves: Effective in presence of maternal antibodies. Calves may be vaccinated from 1
month of age. If primary vaccination is completed before 3 months of age, a booster is
required 6 months later.
Deer calves should commence a vaccination program at 3 months of age.
Booster: Annually, breeding females about 1 month before calving.
Hardjo, and
For the prevention and control of leptospirosis and prevention of urinary shedding of Pfizer
Pomona
leptospira
Primary: Two 2ml doses SC 4 to 6 weeks apart
Calves: 2ml dose at 6 months of age, repeated after 4 to 6 weeks. If under 6 months
are vaccinated, it is essential to revaccinate at 6 months of age and repeat 4 to 6
weeks later.
Booster: Annually about 1 month before calving, in endemic places a 6 months booster
may be required
Hardjo, Pomona and For the prevention of leptospirosis in cattle. Prevents urinary shedding of leptospira Pfizer
Clostridium spp.
when administered prior to exposure.
Primary: Two 2.5ml doses SC 4 to 6 weeks apart. Before period of high risk (autumn to
early summer).
Calves: Efficacious in presence of maternal antibodies. Calves may be vaccinated from
1 month of age. If primary vaccination is completed before 3 months of age, a booster
is required 6 months later.
Booster: Annually preferably about 1 month before calving.
Hardjo, Pomona and For the control of leptospirosis in cattle and the prevention of urinary shedding
Pfizer
Copenhageni
Primary: Two 2ml doses SC 4 to 6 weeks apart. Before period of high risk (autumn to
early summer)
Calves: Efficacious in presence of maternal antibodies. Calves may be vaccinated from
1 month of age. If primary vaccination is completed before 3 months of age, a booster
is required 6 months later
80
Lepto 3-Way
Cattle
Lepto 2-Way
Cattle
Booster: Annually, before period of high risk (autumn to early summer)
Hardjo, Pomona and For the control of leptospira and prevention of urinary shedding
Copenhageni
Primary: Two 2ml doses SC 4 to 6 weeks apart
Calves: From 12 weeks of age. It is essential a booster at 6 to 9 months of age
Booster: Annually each autumn
Hardjo and Pomona
For the vaccination against leptospira and prevention of urinary shedding
Primary: Two 2ml doses SC 4 to 6 weeks apart
Calves: From 12 weeks of age. It is essential to booster at 6 to 9 months of age
Booster: Annually each autumn
81
Virbac
Virbac
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