SHEEP POX 



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^^423. Sheep pox. This affection, known as c/aw/fV, is an 

 acute febrile disease of sheep and goats occurring epizootically 

 and existing in enzootic form in certain parts of Europe, 

 Africa and Asia. It is usually not fatal but a mortality of 

 from 7 to 20 per cent, according to the outbreak, is reported. 

 It is marked by a rise in temperature and general disability 

 followed by the appearance of a series of changes on the bare 

 and merely hairy portions of the skin. These consist of 

 papules, vesicles and pustules which are later covered with a 

 scab. They dry up and drop off in from 15 to 20 days. 

 Observers have distinguished two forms of this affection in 

 sheep, namely, a discrete form and a confined variety. There 

 may be hemorrhages giving the dark or black sheep pox. 



Borrell found that when the scraping from a pustule was 

 suspended in water (mixed) it remained virulent after much 

 dilution. When this suspension was filtered through a Berke- 

 feld cylinder the filtrate was still virulent. It did not pass 

 through a Chamberland filter F. The filtrate retains its viru- 

 lence for a long time. Borrell considers that his results show 

 that the microbe of sheep pox is ultra microscopic and that 

 the cellular inclusions described as parasites of vaccinia, of 

 variola, of davelie, cannot be the true cause of the disease. 

 He believes that the researches should be directed along the 

 lines of those made in connection with contagious pleuro- 

 pneumonia and foot and mouth disease. 



Pathogenesis. According to Hutyra and Marek the 

 cutaneous inoculation of a small drop of pox lymph usually 

 causes in susceptible sheep only a local pox eruption ; in part 

 of the cases, however, especially in lambs or when very virulent 

 lymph is used, there also appears a general pox eruption. In 

 the latter case there forms at the place of inoculation after 

 2-25^ days' incubation a dark red nodule which softens in 

 from four to five days and changes into a vesicle. The latter 

 attains the size of a dollar, its top later sinks, from the interior 

 a little lymph oozes out which later becomes thick, until on the 

 1 2th or 13th day after the inoculation a scab forms with a 

 gradual drying of the pox content. With the beginning 



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