182 SOUTHERN PORK PRODUCTION 



most dense filter. These facts make it difficult to study 

 the organism and to trace its transmission from one place 

 to another. Swine only are susceptible, and the suscepti- 

 bility is very high, especially in the acute form, when 

 frequently an entire herd will become infected very 

 quickly. The disease is also characterized by a very high 

 death rate. The period of incubation, or the time that 

 elapses between the time the hog is exposed and the time 

 it takes the disease, is variable. In some cases it may be 

 two days, and again it may be two weeks, depending on 

 the physical condition of the hog or on its susceptibility, 

 the virulence of the strain and the method in infection. 

 The period of incubation is much shorter in the acute 

 than in the chronic form. 



Among the symptoms are loss of appetite, rise in tem- 

 perature, rapid intoxication and high death rate. Un- 

 fortunately, there are other diseases characterized by 

 similar symptoms and it is only possible to definitely 

 diagnose hog cholera by post-mortem examination. In 

 addition to the ante-mortem symptoms we find a char- 

 acteristic huddling together in pens or nests, stiffness of 

 joints, a cough, especially in the chronic form, a mucous 

 discharge from the eyes and nostrils and red blotches on 

 the skin, especially on the abdomen. At first the animal 

 is constipated, but that is later followed by a persistent 

 diarrhea. In cholera, especially in the chronic form, we 

 find a wide range of symptoms, which result largely from 

 secondary infections with other organisms. These sec- 

 ondary infections frequently complicate diagnosis. In 

 describing the diagnosis of hog cholera it is generally 

 customary to differentiate between the acute and chronic 

 forms, the differentiation being more or less arbitrary and 



