The application of immunological assays for the monitoring and diagnosis of selected infectious diseases, with particular emphasis on neosporosis

The 16 publications presented in this thesis summarise the author’s contribution to seroepidemiological approaches for the diagnosis and monitoring of animal diseases of importance to New Zealand. The first four publications not only contribute to the above in relation to three important animal pathogens, namely Brucella ovis, Mycobacterium avium spp. paratuberculosis and Bovine Leukaemia Virus but also give an insight into more general consideration associated with the optimisation and validation of serological assays, namely regarding the definition and choice of gold standard reference sera, the determination of the cutoff threshold and discrimination between negative and positive reference populations. Two further publications deal with the establishment and validation of serological assays for the diagnosis of Neospora caninum infection and abortion in New Zealand. Then, baseline data were obtained for the sero-prevalence of the infection in dog and cattle populations in New Zealand. Three case studies provided initially information about the kinetics of serological responses after a N caninum abortion outbreak, and information about the usefulness of herd-based techniques rather than individual cowbased abortion diagnoses. A further study provided some early information about the mode of transmission seemingly predominating in New Zealand, which tends to be mainly via post-natal infection, in contrast to evidence provided by overseas researchers. A final case study, a longitudinal study of serological and other responses over a period of three years also provided data on the production effects of N caninum. The dissertation is completed by a number of reviews on sero-diagnosis of N caninum infection, its presence in Australasia and suggests finally control options, based on the present state of knowledge.