Influence of genetics and inbreeding on disease

Genetic influences on disease are far more common in epidemiology than those expressed through the phenomenon of inbreeding. However, it is useful to explore the associations between inbreeding and the occurrence of disease before considering the wider role of genetics, as the influence of inbreeding is most overtly seen in simple Mendelian diseases. In such cases, a single locus is responsible for disease manifestation, while in more complex diseases, genetic influences are commonly associated with a number of loci. While this article examines the role of genetics in cattle diseases, with a particular emphasis on inbreeding, all the principles discussed can be extended directly to other livestock, horses and companion animals.