Transactions of RHASS Volume 1940 - Page 042
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| Year | 1940 |
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72 SCRAPIE. that of the Saxon Merinos. Hurtrel D’Arboval, however, believes that there is evidence that the disease was known in Germany previous to 1750, that is at a time earlier than the first introduction of Merinos to that country. Stockman suggests that the first recognition of scrapie in France seems to have been made after the Merino importations of 1867 -7 6 ; on the other hand, thisis difficult to reconcile with the fact that scrapie existed in France even previous to 1848 when Roche—Lubin published an accurate account of the disease. Stockman also pointed out that flocks of Merinos were imported into England about 1799, and that it was about this time that the prevalence of the disease was first recorded by English writers. He further Suggested that, since the Merino was crossed with the Leicester, this might account for the occurrence of scrapie in the Border Leicester breed to-day. This view, in the writer’s opinion, should be accepted with reserve. Bertrand, Carré, and Lucam state that in the literature there exists no reference to the occurrence of scrapie in the Merino or in its several crosses, and, in point of fact, it is not improbable that scrapie existed in this country long before the end of the eighteenth century, and that it was only when serious efforts to effect wool improvement increased the economic importance of sheep husbandry—and incidentally brought about the introduction of the Merino—that the disease was more clearly recognised and became the subject of record. In France scrapie is largely confined to the Department of Aveyron, where it is particularly prevalent in the Larzae breed. In Germany and Austria, according to Friedberger and Frohner, the disease affects the Electoral sheep rather than those of the large, coarse Negretti breed, and is most prevalent in Saxony, Moravia and Silesia, in which provinces the Electoral type of sheep is commonly bred. The disease appears to be more frequently encountered in Prussia and Saxony than in South Germany. BREED INCIDENCE. In this country sheep are the only animals known to become aflected with scrapie ; on the Continent the disease has been recorded also in the goat, but the accuracy of the available records is doubtful. In Britain scrapie commonly affects the Border Leicester breed and its crosses, the Half-Breds (Border Leicester—Cheviot cross), and the Cross Suffolks (Suffolk—Half-Bred cross). It also frequently occurs in the pure Cheviots. Other breeds are not immune to the disease, but its incidence in Scottish Blackfaces is remarkably low. Scrapie is relatively rarely SCRAPIE. 73 met with in the Border Leicester—Blackface crosses, the sis-called Greyfaces or Mules. AGE INCIDENCE. Scrapie is very seldom observed in sheep under eighteen nmnths of age. Gaiger, however, records a case in a thirteen- months-old ewe, and the writer has records of its occurrence i'. a fifteen-months-old ram and also in a virgin gimmer and i» a lambed gimmer of the same age, while Stockman states mat he has observed its occurrence in sheep at the ages of inc and a half, eleven, and fourteen months. It most wmmonly attacks sheep of about two years of age, whether ihese be lambing ewes, virgin ewes, rams or wethers (castrated rules), but the disease is seldom seen in wethers, as they are suallv sent to the abattoir before they are two years old. There appears to be no maximum to the age incidence. and «uses of scrapie in nine-years—old sheep of both sexes have lmen observed. PREDISPOSING FACTORS. (1) Environmental Conditions—In this country scrapie is mainly found in parts of Northumberland and in the eastern .iorder counties of Scotland, and it would now appear to be .shnost entirely absent from those parts of England in which t once prevailed. The precise significance of this observation is difficult of 'uterpretation, but there is a considerable volume of evidence which Suggests that the occurrence of scrapie is, at least to omc extent, controlled by environmental conditions. This .uvolves the assumption that in non-scrapie areas there exist one or more factors which in some manner tend to prevent 1he continuance of the disease, or alternatively, that in scrapie - .u-eas there obtain certain factors which act as excitants to its production. It has been frequently observed, for example, that when sheep from infected flocks are transferred to parts of the «ountry in which scrapie does not occur as an enzootic the disease may develop in these sheep or their immediate progeny, but it soon tends to disappear. Again, when a lot of lambs irom a scrapie flock has been divided and sold to two different farms, scrapie may develop on one of these, but may fail to manifest itself on the other. Similar experiences are recorded by Continental observers. There is a general (although perhaps unfounded) belief among shepherds that the disease is more likely to become prevalent in light as distinct from heavy, clay soils. VOL. LII. F |
| Title | Transactions of RHASS Volume 1940 - Page 042 |
