LECTURE XLII 

 HOG CHOLERA 



To be considered hog cholera, the disease must be infectious 

 by pen exposure, and an attack followed by recovery must give 

 immunity ; the blood from a diseased hog should be virulent and 

 capable of reproducing the disease ; the living animal should 

 show the symptoms later described ; and the carcass of the dead 

 animal should show the symptoms given under {lutopsy. 



Variations in virulence. — Outbreaks of hog cholera vary 

 greatly in virulence and symptoms. In some outbreaks the 

 virulence is marked, and the hogs die quickly ; in others a ma- 

 jority of the cases assume the chronic type, the hogs do not die 

 so quickly, and the percentage of loss is not so gi-eat. 



Various gradations may appear between cases of the utmost 

 virulence and those of the milder type. 



General symptoms. — Lack of appetite, fever, and thirst are 

 early symptoms of hog cholera. The hair becomes harsh and 

 dry, the eyes may be watery, and the gait becomes weak and 

 irregular, with imperfect control of the hind legs. The skin 

 around the flanks and fore legs and abdomen may become 

 purple ; that of the ears frequently becomes much inflamed, and, 

 if the hog lives for several days, may assume a scabby appear- 

 ance. Sometimes the tips of the ears slough off. The sick hogs 

 soon separate themselves from the rest of the herd, being dis- 

 posed to hide in sheltered places, and are little inclined to move 

 about. Chronic cases lose flesh rapidly and sometimes show 

 extreme disturbance of the nervous system, exhibited in partial 

 or complete paralysis of the hind parts, or extreme nervousness. 

 The cough is usually short and hacking. Occasional constipa- 

 tion appears among the earliest symptoms, but is usually not 

 noticed ; later, diarrhea appears. In some of the very acute 

 eases which appear at the beginning of an outbreak, the animals 

 die very suddenly — sometimes before the owner realizes that 

 they are sick. Later in the history of the disease, as it appears 

 in a herd, the cases tend to assume the more chronic type. 



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