Genetic markers and Bovine Johne's disease

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Johne's disease (JD) is a disease with great economic implications to the dairy industry and is also attractingsignificant public health concern owing to the possible zoonotic nature of its causative bacteria,Mycobacterium avium subsp. paratuberculosis. The lack of availability of vaccines with high efficacy as wellas effective treatments has hindered control of JD worldwide. Given its heritable nature, as indicated in variousstudies, one means of reducing the incidence of JD is by employing genetic selection in breeding programs toproduce offspring with enhanced disease resistance. To achieve this, it is necessary to identify genetic markersassociated with JD and to assess their biological relevance. Over the past decade, a number of genomic studieshave identified different genetic markers associated with JD. Inconsistent findings from these studies suggestthat JD is a complex disease that is polygenic in nature with many potential genetic markers influencing diseaseresistance. There is a need to further validate these genetic markers in independent populations before they canbe used in genetic selection programs, and this is the aim of the present study. The specific objectives are to: a)validate and confirm previous associations with genetic markers and JD in a Canadian Holstein population, b)assess potential impact of these markers on production and health traits, and c) characterize their biologicalrelevance in vitro using genetically modified bovine cell lines. New knowledge obtained from this study willhelp dairy industry move forward to enhance resistance to JD through genetic selection.