Investigation into the disease of sheep called "scrapie" (Traberkrankheit, la tremblante) : with especial reference to its association with sarcosporidiosis / by J.P. M'Gowan ; with an appendix on a case of Johne's disease in the sheep.
- M'Gowan, J. P. (John Pool)
- Date:
- 1914
Licence: Public Domain Mark
Credit: Investigation into the disease of sheep called "scrapie" (Traberkrankheit, la tremblante) : with especial reference to its association with sarcosporidiosis / by J.P. M'Gowan ; with an appendix on a case of Johne's disease in the sheep. Source: Wellcome Collection.
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![by veterinarians. There is much evidence indicating that the disease is not hereditary. The principal point is that the disease occurs among sheep that are not pure bred, such as English and German sheep bred for mutton. It is alleged that goats are also attacked. The disease also occurs among pure-bred sheep derived from perfectly healthy parents. Furstenberg records an outbreak that was so severe that almost every animal in a herd of 500 became ill and one-third of them died.! Cases of this sort absolutely exclude the possibility of heredity having anything to do with the transmission of the disease. Evidence pointing in the same direction is that the progeny of certain rams become ill in one district and not in another, and, further, the complete disappearance of the disease from herds that are severely affected when the herds are transferred to other districts. Even this factor was not considered completely satisfactory by the supporters of the theory, other causes being also blamed, such as an excessive use of young rams, feeding with rich food, or, on the other hand, with poor food, and sudden changes of food. These factors have not been shown by more recent investigations to play any part in the pro- duction of the disease. The fact that the disease occurs in certain districts, in some cases in particular parts of these districts and especially in damp marshy places, suggests that it is due to an infection of some sort. The in- fection theory put forward by Richthofen has more recently found supporters in Besnoit and Morel, although these admit the possibility that it may be due to an intoxication set up by some food-stuff. Cassirer has been unable to transmit the disease to sound animals by the transfusion of blood, but in the blood and cerebro-spinal fluid he found large cocci, which after intravenous inoculation persisted in the blood of healthy sheep for long periods and then disappeared. One experimental sheep died after a year from exhaustion without having shown any symptoms of the disease. A special predisposition on the part of certain breeds of sheep accords well with the theory of infection. The special susceptibility of the Electoral sheep may be due to the excessive improvement of the breed, to inbreeding, and to pampering. Susceptibility to other con- tagious diseases is seen under similar circumstances. The occurrence of the disease after the introduction of fresh stud animals and the subsequent spread, are consonant with this theory. On the other hand, a spontaneous occurrence of the disease does not completely militate against the possibility that the disease is of an infectious nature, in that it is not always easy to prove that an infective material has not been introduced. Describing the symptoms, they say (p. 759) :— The most striking symptoms in the early stages are, as a rule, excitability and fright. The animals have a scared look, and the approach of a person or animal is sufficient to so frighten them that 1 These would appear not to be cases of the disease under consideration. —[J. P. M‘G.]](https://iiif.wellcomecollection.org/image/b32862040_0042.jp2/full/800%2C/0/default.jpg)
