138 DISEASES OF SWINE 



tribution depends to some extent on the same con- 

 ditions as those mentioned in connection with the 

 hog cholera germ. 



People, dogs, and birds are not important agents 

 in the distribution of the disease, and it does not 

 Seem to spread readily through the food supply 

 and as a result of filth. Buying hogs from infect- 

 ed herds and exposure to the disease at stock 

 shows and fairs are, perhaps, the most common 

 method of distributing the disease. Wind and 

 dust are common carriers of the swine plague 

 germ, and during dry, windy weather in the fall 

 of the year, swine plague may spread rapidly 

 among the hogs in a neighborhood and exist as a 

 distinct disease. Irritation to the lungs from dust 

 and lung worms seem to act indirectly in causing it. 



Period of Incubation. — The time that elapses be- 

 tween the exposure and appearance of the symp- 

 toms is shorter than in hog cholera. If the swine 

 plague germs are active, they multiply very rapid- 

 ly in the system and produce disease in a short 

 time. 



Symptoms. — In the large majority of cases, 

 there is no noticeable difference between the 

 symptoms of hog cholera and swine plague. It is 

 only when the lungs are extensively inflamed, that 

 the stockman, or veterinarian is able to dififer- 

 entiate between the two diseases by studying the 

 symptoms alone.' The recognition of swine plague 

 is based largely on such symptoms as coughing, 

 and labored, painful, and oppressed breathing. 



