. Activities handbook. Veterinary medicine. An advanced case of scrapie. Scrapie studies Each outbreak is carefully studied to estab- lish the epidemiology of the disease. Particu- lar attention is given to symptoms, laboratory findings, age, sex, breed, history, and pedigree of each infected animal, movements from in- fected flocks, and the possible source of the outbreak. During the 7 years the eradication program has been in effect in this country, it has not been possible to identify the source of several outbreaks. The majority, however, fall into a pattern and indicate spread from a limi
. Activities handbook. Veterinary medicine. An advanced case of scrapie. Scrapie studies Each outbreak is carefully studied to estab- lish the epidemiology of the disease. Particu- lar attention is given to symptoms, laboratory findings, age, sex, breed, history, and pedigree of each infected animal, movements from in- fected flocks, and the possible source of the outbreak. During the 7 years the eradication program has been in effect in this country, it has not been possible to identify the source of several outbreaks. The majority, however, fall into a pattern and indicate spread from a limited number of common foci. Such foci—usually identified as source flocks—are now being slaughtered. Approximately 80 percent of the infected sheep in this countiy either were imported or were the immediate progeny of sheep of for- eign registry. The broadened Canadian pro- gram should materially reduce the possibility for further introduction of scrapie through sheep imported from Canada. Exposed sheep and their immediate progeny from 1,800 flocks have been slaughtered. Pres- ently, some 1,500 flocks are receiving the re- quired 6-months' inspection. In November 1956, more than 2,000 flocks were under inspec- tion. These routine inspections have helped locate infected animals. Almost 50 percent of the 91 outbreaks were found in this manner. Sheep under 18 months of age seldom show symptoms of natural scrapie. Only one of the IGl infected sheep in this country was 18 months old; the others were older. Three were more than 71a> years old. The great majority were from 2\-^ to 4 years old with most being about 3 years of age. Mortality rates are difiicult to determine with certainty. When an outbreak occurs, the entire flock is slaughtered before additional cases have time to appear. Of the 161 confirmed cases in the United States, 151 were Suffolk sheep and 10 were Cheviots. Although the majority of cases have occurred in one breed, it is generally believed that sheep of an
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