Course. Diagnosis. 313 



If an outbreak has appeared in a large flock the cases first 

 appear at mtervals of 10 to 14 days, later however in more rapid 

 succession, until finally, with the exception of about 2 to 3%, 

 all animals have become affected. In some cases only a small 

 part of the herd becomes affected at first, and only 3 to 4 weeks 

 later when the animals that were stricken first already show 

 indications of recovery does the disease break out suddenly 

 in a great number of sheep, and finally after a further interval 

 all of the animals of the flock which have been spared become 

 affected. 



Diagnosis. The character of the exanthema and the typical 

 course of the disease as a rule make a positive diagnosis pos- 

 sible. If the danger of contagion exists the first prodroinal 

 symptoms are sufficient to arouse a suspicion of the disease, 

 otherwise however the diagnosis should be suspended until 

 typical vesicles have developed from the nodules. The pres- 

 ence of vesicles and pustules is not absolutely necessary in the 

 clinical develox>ment of the disease, as was shown by recent 

 German and Algerian observations, and therefore in such an 

 atypical course a papular exanthema is sufficient to establish at 

 least a suspicion of the disease, especially when such lesions 

 develop in association with fever and catarrh of the mucous 

 membranes. The diagnosis may be confirmed later by inocula- 

 tions of the contents of the nodules into healthy animals. 



The disease may be mistaken for scabies and pustular 

 eczema, especially in the stage of pustule and scab formation. 

 In these diseases however there are no severe prodromal symp- 

 toms preceding the development of the lesions, besides this, 

 eczema is not infectious, and in its course no larger vesicles 

 develop, while scabies, although infectious, spreads very slowly, 

 and scabies mites may be readily demonstrated with the micro- 

 scope in the scabs and crusts. 



Prognosis. In cases in which the pox eruptions are few and 

 the individual papules develop in the regular order the prog- 

 nosis is favorable. On the other hand in those cases in wliicli 

 the exanthema extends over a larger portion of the body, and in 

 which the vesicles show a tendency toward coalescing, it is 

 doubtful. Hemorrhages are always unfavorable indications, 

 irrespective of the stage in which they appear. 



Very old or very young animals show, under otherwise like 

 conditions, feeble resistance and sucking lambs especially be- 

 come severely ill with otherwise mild pox on account of the usual 

 association of gastro-intestinal catarrh. In flocks where the 

 animals are confined in narrow quarters the disease runs a more 

 unfavorable course than in animals kept out of doors. In the 

 latter again great heat or damp chilly weather has a bad effect. 

 Sheep which come from localities in which pox is prevalent 

 become more readily affected than those which come from 

 localities where the disease has not existed for a long period. 



