Identification of genetic regions associated with tolerance and Infection to Johne's Disease in cattle using a fine-mapping approach

Johne's disease is an incurable illness of ruminants, caused by Mycobacterium avium subspecies paratuberculosis (Map). Once an animal is exposed to Map it can become infected or resist infection. Susceptible animals may develop Johne's disease with different severity levels or exhibit different levels of tolerance. Selection of animals that are resistant or tolerant to Johne's disease would reduce economic losses and reduce disease prevalence. Tolerance was measured by there relationship between fitness (Map fecal shedding) and infection intensity (Map tissue infection); infection was determined by the presence of Map in four tissues. We previously identified associations with a region on BTA 3 and Map tissue infection and on BTA15 with tolerance to Johne's disease using a whole-genome analysis. The objective of this study was to confirm the association on BTA3 and BTA15. On BTA15, 54 SNPs were used to interrogate a 193kb region and on BTA3, 42 SNPs were chosen for a 235kb region. Sixteen SNPs on BTA15 and 18 SNPs on BTA3 were removed due to low minor allele frequencies (10%). Association analyses were conducted with the Wald test (tolerance) and the Chi-square test (Map tissue infection). A region of 32kb was associated with tolerance (P<0.03), and an 86kb region was associated with Map tissue infection (P