Breed predisposition for BSE: epidemiological evidence in Bavarian cattle

We present epidemiological data from Bavaria that indicates that animals of the Brown Swiss (BS) cattle breed might be more susceptible to BSE than animals from other breeds, both in terms of disease prevalence and length of the incubation period. BS animals were disproportionately represented among the BSE cases (BS represented about 9% of the susceptible population but 27% of actual cases). BS were slaughtered at a higher age (5.8 years vs. 5.0 years for other breeds), and there is a higher prevalence of feeding proprietary feeds to BS calves than calves from other breeds. There was no difference in the recorded feeding practice of BSE-positive animals from BS or other breeds. These results would lead to expect a higher prevalence of BSE in the BS population, with BS BSE animals being of equal age or older than BSE animals from other breeds. In contrast, median age at BSE detection was significantly lower in BS animals than in other breeds (61.4 vs. 68.8 months). There was no difference in the identification categories of BSE between BS animals and animals of other breeds that could explain this difference in age. BS cattle are reported to have more octapeptid repeats in the prion protein gene than other breeds, which could account for shorter incubation periods and higher susceptibility. These observations suggest that BS animals and their tissues should be used in further studies into genetic determinants of BSE susceptibility in cattle.