State-of-the-art review of goat TSE in the European Union, with special emphasis on PRNP genetics and epidemiology

Abstract

Scrapie is a fatal, neurodegenerative disease of sheep and goats. It is also the earliest known member in the family of diseases classified as transmissible spongiform encephalopathies (TSE) or prion diseases, which includes Creutzfeldt-Jakob disease in humans, bovine spongiform encephalopathy (BSE), and chronic wasting disease in cervids. The recent revelation of naturally occurring BSE in a goat has brought the issue of TSE in goats to the attention of the public. In contrast to scrapie, BSE presents a proven risk to humans. The risk of goat BSE, however, is difficult to evaluate, as our knowledge of TSE in goats is limited. Natural caprine scrapie has been discovered throughout Europe, with reported cases generally being greatest in countries with the highest goat populations. As with sheep scrapie, susceptibility and incubation period duration of goat scrapie are most likely controlled by the prion protein (PrP) gene (PRNP). Like the PRNP of sheep, the caprine PRNP shows significantly greater variability than that of cattle and humans. Although PRNP variability in goats differs from that observed in sheep, the two species share several identical alleles. Moreover, while the ARR allele associated with enhancing resistance in sheep is not present in the goat PRNP, there is evidence for the existence of other PrP variants related to resistance. This review presents the current knowledge of the epidemiology of caprine scrapie within the major European goat populations, and compiles the current data on genetic variability of PRNP.

Figure 1.

Distribution of goat scrapie cases reported in 27 EU member states, Iceland, Switzerland, and Norway during the period from 2002 to 2007. Numbers outside parentheses indicate the total goat TSE cases reported by individual EU member states in 2007, while those inside parentheses indicate the number of atypical goat scrapie cases. Numbers are not shown for countries with no reported cases of goat TSE during 2007. The shading indicates the distribution of goat TSE cases during the period from 2002 to 2007, according to the scheme outlined in the legend.