210 



VETERINARY STUDIES 



the surface. Small ulcers may occur in the back part of the 

 mouth, in the gullet and stomach. 



Very small hemorrhages are found on the surface or through 

 the deeper structure of the kidneys. 



Cause. — Hog cholera is a very infectious disease which has 

 its origin in a living' virus. The virus particles are probably 

 so small as to be invisible with our best microscopes and are 

 capable of passing in some form through a laboratory germ 

 filter. 



This is probably a complicated disease in most outbreaks. 



The filterable virus is evidently 

 the principal and specific infec- 

 tion. With this virus there is 

 usually one or more secondary 

 invaders. One of the secondary 

 invaders may cause or con- 

 tribute to the chronic lesions, 

 ulcers of the digestive tract, for 

 instance. Another may cause 

 or contribute to the lung and 

 pleura lesions. This accounts, 

 in part, for the wide variations 

 in symptoms and lesions. 



Infection usually occurs by 

 way of the mouth, and the 

 period of incubation is from 8 

 to 14 days. Simple conditions of keep and feed have much to do 

 with making the animals susceptible, but food and surroundings 

 cannot serve as the first cause of hog cholera. Predisposing 

 factors must be given due consideration, but the most important 

 things to remember are the sick hog and the living virus and that 

 hog cholera never appears without the infection which may be 

 easily carried from one place to another. 



If the hog is fed exclusively on corn diet and kept overfat ; 

 or if it is kept shut up in dark, damp, and perhaps filthy pens, 

 it will not be able to resist any disease as would the hog kept 

 under more favorable conditions. But these are only contribut- 

 ing factors. The laws of hygiene cannot be neglected without 

 rendering any animals more susceptible to disease ; but no de- 

 gree of ordinary vigor can give assurance of immunity to 

 cholera. 



Fig. 73. — Hog Cholera. 

 (M. H. B.) 



Hemorrhages (dark spots) on 

 iliapliragin. Hemorrhages are char- 

 acteristic. 



