Goat Genetics and Scrapie
Genotyping sheep for susceptibility to scrapie infection is an internationally recognized tool in scrapie disease control programs in many countries, including Canada's National Scrapie Eradication Program. At the present time, studies on goat genetics and scrapie susceptibility are more limited and less clear. As a result, genotyping goats for susceptibility to scrapie infection is not currently used as a disease control measure internationally nor a tool used in Canada's National Scrapie Eradication Program.
What is Genotyping?
A genotype is an individual's collection of genes. Like all mammals, goats receive one allele for each gene from their dam (doe) and one allele from their sire (buck). Alleles are the different versions of a gene. Scrapie genotyping is routinely used in sheep and refers to testing that reveals the specific alleles inherited for the animals' prion gene that makes an animal more or less susceptible to scrapie.
What do we know about scrapie genotyping in goats?
International research is ongoing on goat genotypes and susceptibility to scrapie. Currently there is no international consensus on what constitutes a resistant genotype in goats. In the literature, multiple variations in the goat prion gene have been associated with levels of scrapie resistance, depending on the breed of goat, the originating region of the animal and the individual study. Variable protective effects against scrapie have been reported for alleles S127, M142, S146, D146, H154, Q211 and K222 in goats. Research has also been conducted on a small population of goats in Canada to determine if certain goat genotypes were associated with scrapie positive or negative goats. It is still premature to apply these research findings to all goat herds and breeds in Canada, especially considering the different findings in the various published studies of goat genetics around the world. Further research is needed on both potentially resistance genotypes and on the genetic make-up of the Canadian goat population.
Is scrapie genotyping used in the National Scrapie Eradication Program?
It is important to understand that scrapie genotyping is not disease testing. Scrapie genotyping in sheep is a tool that is used by the CFIA during disease control actions with an infected sheep flock in order to minimize the number of sheep ordered destroyed in the flock. At this stage, the research on Canadian goat genetics and potential scrapie resistance is not enough to trigger goat genotyping as a tool to be used during CFIA disease control actions. The CFIA continues to contribute to and evaluate new science as it applies to goat scrapie, and when possible, will transfer it to National Scrapie Eradication Program.
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