GENETIC-RESISTANCE TO AVIAN VIRUSES

Viral infections of poultry can be catastrophic in terms of both welfa re and economics, and although vaccines have been very successful in c ombating these diseases, new forms of viruses have evolved which prese nt increasing difficulties for vaccine control. Differences in genetic susceptibility are known to exist for many of the major viral pathoge ns of poultry. Consequently, an increase in the level of genetic resis tance provides a possible means of enhancing protection of flocks. Thi s is particularly feasible where specific resistance genes have been i dentified, as in the case of avian leukosis and Marek's disease, and t he development of genetic maps of the chicken has offered new possibil ities for the identification of further resistance genes. It has also become clear that there are genetic differences in the response to liv e attenuated vaccine viruses, and new possibilities exist to manipulat e the genetics of host flocks so that the effect of vaccination can be optimised.