Genetic Resistance to Johne's Disease in Four Cattle Breeds

A Candidate Gene Case Control Study, Preliminary Results

Abstract

Paratuberculosis is a chronic debilitating, infectious disease of ruminants, caused by Mycobacterium avium subsp. paratuberculosis, and characterized by progressive weight loss and profuse diarrhea. The disease has been suspected to have a genetic component and estimations of heritability of 0.15 have been reported. Crohn's disease (CD) is an inflammatory bowel disease in humans resembling many aspects of paratuberculosis. Susceptibility to CD has a strong genetic component and one gene involved has been identified as CARD15 (Caspase recruitment domain 15), with a role in the intracellular recognition of bacterial cell walls as a part of the immune response. The association between mutations in this gene and increased risk of CD has been extensively described. Since Johne's disease has been demonstrated to have a genetic component and genetic variation for infection resistance exists in cattle, CARD15 could also determine differences in resistance to paratuberculosis in the bovine. This candidate gene study focused on determining the alleles present in the CARD15 gene in a population of infected and of noninfected cows. Our objective was characterizing the distribution of two polymorphisms in this gene and testing their association with paratuberculosis infection in Florida cattle with the aim of finding resistance alleles useful in livestock selection.