Epidemiologic analysis of reported scrapie in sheep in the United States: 1,117 cases (1947-1992)
Wineland, N.E.; Detwiler, L.A.; Salman, M.D.
Journal of the American Veterinary Medical Association 212(5): 713-718
1998
ISSN/ISBN: 0003-1488 PMID: 9524648 Document Number: 496969
Records for scrapie-positive sheep flocks and sheep with clinical signs consistent with scrapie reported to the USDA from 1947 through 1992. Records from the United States Department of Agriculture scrapie control and eradication programme were abstracted, entered into a computer database and analysed. 1117 sheep from 657 flocks located in 39 states were scrapie-positive during the study period. There were no seasonal or spatial trends. Mean yearly proportion of scrapie-positive flocks increased slightly from 1965 through to 1992. 168 rams and 949 ewes were reported to be scrapie-positive during the study period, which was slightly more rams than expected if the disease was equally likely to affect rams and ewes. Suffolks (972 of 1117; 87%) and Hampshires [Hampshire Down] (68 of 1117; 6%) were most commonly affected. It is suggested that the prevalence of scrapie in sheep in the USA is unknown and that bias in this study may have resulted from inconsistencies in available information, misclassification of sheep with clinically suspicious signs of scrapie, and changes in the national scrapie control and eradication programme that may have affected willingness of owners and veterinarians to report potentially infected sheep.