Genetic variation in disease resistance among farm animals

Abstract

This background study paper reviews the results of scientific investigations involving genetic control mechanisms for resistance/tolerance in farm animals to specific viral, bacterial, parasitic and prion diseases. The paper presents the most prominent documented examples for resistance/tolerance in cows, sheep and goats, pigs and poultry. The importance of genetically heterogeneous populations is highlighted, particularly as they impact response to epidemics, their duration, lower mortality rates, etc. Genetic studies on resistance in farm animals to a variety of etiological infectious agents can be determined at three genetic levels of variation: species, breed and unique genetic variation among individual animals. Depending upon the etiology of disease and the available animal resources, strategies for developing genetic disease management can be developed at the following levels: selection of breeds that are particularly well adapted to the local environment, breeding methods which include the introduction of genes exhibiting genetic resistance/tolerance towards pathogenic organisms, and the selection of individual animals with a high level of specific pathogen resistance. The most recent epidemic zoonoses illustrate how important it has become to develop global mechanisms for control of zoonoses and consequently the vital role of veterinary services in disease control.