Epidemiology and control of leptospirosis in farmed deer in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Clinical Science at Massey University, Palmerston North, New Zealand

dc.contributor.authorAyanegui Alcérreca, María Alejandra
dc.date.accessioned2010-07-20T03:42:52Z
dc.date.availableNO_RESTRICTIONen_US
dc.date.available2010-07-20T03:42:52Z
dc.date.issued2006
dc.descriptionMissing pages 93, 264 & 313 from electronic and Vault (preservation) copy.
dc.description.abstractLeptospirosis has been reported in farmed deer in New Zealand since 1980 but knowledge was limited. Studies presented in this thesis investigated the epidemiology and distribution of infection associated with serovars Hardjobovis, Pomona, and Copenhageni in farmed deer, efficacy of a vaccine and the influence of maternally derived antibody, and aspects of exposure of humans to leptospirosis. Serology, bacteriology, and pathology were employed as determinants of infection and vaccine efficacy. A serological survey of 2016 deer from 110 herds confirmed leptospirosis throughout New Zealand with 61.3% of herds infected with Hardjobovis and 3.6% with Pomona alone, 16.4% with dual infections with those serovars, and none with Copenhageni, giving an overall herd prevalence of 81.3%. Epidemiological studies involved serological analysis of samples from a serum bank involving weaner, yearling and adult deer (n=10/group) from 15 farms sampled 3-monthly for 21 months, and intensive blood and urine sampling of young deer on three farms over 1-2 production cycles (n=15-65/group). Infection with Hardjobovis followed an age-related endemic cycle with some animals infected by 3-4 months of age and seroconversion peaking at up to 57% at 12-15 months and mild kidney lesions typical of a host-adapted organism. Infection with Pomona followed an epidemic pattern with seroprevalence of up to 100%, more severe kidney lesions, clinical signs and evidence of reduced growth and reproduction, typical of an accidental host relationship. Leptospira were observed in 30.4% of urine samples and 37.0% of kidneys. Vaccination with "Leptavoid 3" (Schering-Plough Animal Health Ltd) was studied on one non-infected, one Hardjobovis infected, and two dual Hardjobovis/Pomona infected herds. Vaccination produced sustained titres in uninfected young and adult deer, and no maternally derived antibody interference was observed in progeny vaccinated at approximately 3-4 months of age. In infected herds, vaccination enhanced seroprevalence and antibody titres, and reduced urine shedding by 44% and culture from urine and kidneys by 37% in the face of continued natural challenge. Analysis of previous data combined with pooled data from the above studies, indicated that 73.0% of lines and 29.0% of individual deer at slaughterhouses had kidney lesions indicative of leptospirosis with a relative risk (RR) of 1.08 and 1.6 for the relationship between seropositivity to Hardjobovis and Pomona, respectively. The overall RR between positive serology, lesion and culture was 2.1. The kidney culture rate ranged from 2.5-33% between herds demonstrating significant risk of exposure to humans, particularly slaughterhouse workers. This study has provided an understanding of the epidemiology in farmed deer and control options available to the industry.en_US
dc.identifier.urihttp://hdl.handle.net/10179/1470
dc.language.isoenen_US
dc.publisherMassey Universityen_US
dc.rightsThe Authoren_US
dc.subjectHardjo-bovisen_US
dc.subjectPomonaen_US
dc.subjectEpidemiologyen_US
dc.subject.otherFields of Research::300000 Agricultural, Veterinary and Environmental Sciences::300500 Veterinary Medicine::300503 Epidemiologyen_US
dc.titleEpidemiology and control of leptospirosis in farmed deer in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Clinical Science at Massey University, Palmerston North, New Zealanden_US
dc.typeThesisen_US
massey.contributor.authorAyanegui Alcérreca, María Alejandra
thesis.degree.disciplineVeterinary Clinical Scienceen_US
thesis.degree.grantorMassey Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophy (Ph.D.)en_US
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