VARIOLA— POX 375 



cow to cow in the same manner. The disease may also be 

 propagated by contaminated litter, forage, food, etc., which 

 explains its occurrence in heifers, steers, and bulls. 



Symptoms. — ^The period of incubation is four to seven days. 

 The prodromal symptoms are usually so mild as to be over- 

 looked. Occasionally symptoms of general disturbance 

 (fever, loss of appetite, languor) precede the eruption. The 

 first local symptom noted is usually a sensitiveness of the 

 teats during milking. In two to three days on or at the base 

 of the teat and on the udder appear pea-sized papules which 

 in forty-eight hours form vesicles the size of a bean. The 

 vesicles contain a clear fluid and are often pearl-like in color. 

 On the udder they are usually round and on the teats oval in 

 form. They are noted best on the udder, near the base of the 

 teat where they are less hable to be broken by the milker's 

 hands. The vesicles are usually surrounded by a red zone. 

 When intact they are frequently umbilicated. In eight to 

 fourteen days pustules appear that erupt and dry to form 

 crusts which slough leaving shallow pits. As a rule only a 

 few vesicles occur, usually not over a dozen and occasionally 

 only one or two can be found. The eruption does not take 

 place simultaneously, several days may elapse between the 

 formation of individual or groups of vesicles. Those which 

 form later are generally smaller than the earlier ones. 



As the vesicles, especially those which form on the teat, are 

 crushed during milking, secondary changes due to traumatism 

 and extraneous infection are usual. From the frequent irri- 

 tation of milking there form ulcers with eventually indurated 

 borders which heal only after several weeks. 



Parenchymatous mastitis is a common complication, espe- 

 cially where milk tubes are employed to draw off the milk 

 from the affected teats. In males the disease is very rare and 

 is said to involve the scrotal region. 



A generalization of the eruption is very uncommon. In 

 the few cases recorded, the vesicles appeared in the inner side 

 of the thigh, on the croup, body, chest, neck and muzzle. 



Diagnosis. — ^The tj^pical exanthema, its spread from cow to 

 cow and to the hands of the mUkers, the absence of general 

 sj-mptoms and the benign course characterize the disease. In 



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