Proceedings of the 10th International Colloquium on Paratuberculosis

#65
A deer model for heritable resistance to MAP infection and Johne’s disease
Frank Griffin, Rory O’Brien, Simon Liggett, Colin Mackintosh
University <strong>of</strong> Otago, New Zealand; AgResearch Invermay, New Zealand
Objective: To identify breeds <strong>of</strong> deer with polarized phenotypes for susceptibility or resistance to MAP Infection.
Materials and Methods: An ELISA test was used to screen naturally infected deer stud herds to identify
<strong>the</strong> relative prevalence <strong>of</strong> infection from eight uniquely different deer breeds (genotypes). Seropositive animals
were necropsied and detailed microbiological and histopathological examinations carried out to confirm <strong>the</strong>ir
infection status. Cross-bred hybrids were also examined. Followup studies were carried out using embryos
from <strong>the</strong> distinct genotypes studied in <strong>the</strong> herd screen.
Results: The different deer breeds had MAP seroprevalence ranging from 0 - 80%. Animals with a given
genotype displayed similar infection rates when farmed in different herds. The influence <strong>of</strong> genotype was explored
fur<strong>the</strong>r using embryos derived from different breeds as purebred or hybrid lines. The advantage using
embryos is that exposure risk from <strong>the</strong> dam was controlled as all embryos were transferred randomly into test
negative recipient hinds. Hybridising parental breeds that displayed low infection prevalence (0%) with breeds
showing high prevalence (58%) produced <strong>of</strong>fspring with intermediate prevalence (24%) suggesting Mendelian
heritability <strong>of</strong> resistance traits.
Conclusion: High levels <strong>of</strong> line breeding are carried out within <strong>the</strong> New Zealand deer industry where
some <strong>of</strong> <strong>the</strong> top performing stags are overrepresented in <strong>the</strong> gene pool. Selection criteria have been largely
focused solely on superior production (venison and antler) and temperament. This selective breeding strategy
within deer studs appears inadvertently to have selected animals with genotypes that display extremes <strong>of</strong> susceptibility
or resistance to mycobacterial infections (tuberculosis and paratuberculosis). The purebred lines <strong>of</strong>
deer that display <strong>the</strong>se extreme phenotypes are being studied to identify <strong>the</strong> genes that contribute to susceptibility/resistance
using immunoassays for innate and adaptive immunity. Polymorphisms in Immune response
genes (SNPs) and <strong>the</strong> mononuclear cell transcriptome <strong>of</strong> <strong>the</strong>se animals is being studied using 454 sequencing.
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