Study of endemic scrapie in a flock of "Ile de France" sheep.

An "Ile de France" flock was studied over a period of 5 years. The authors found similar results concerning incidence and age of onset of scrapie to those found in the English literature. A close relationship was established between the age of the dam at parturition and the age of the progeny at onset of scrapie. In the later years of our study, scrapie was detected in younger animals than in the earlier years, suggesting a phenomenon of genetic "anticipation". Increased fecundity in this endemically affected flock might represent a form of selection which favorises the occurrence and maintenance of the disease within the flock.