CHRONIC CHOLERA 181 



sick animal may be noted to be just a little off feed at times, but 

 the next day may be eating again as usual. This hidden nature of 

 the symptoms may lead to a great deal of damage. Hogs suffering 

 from these very mild cases of cholera are often bought as apparently 

 healthy animals and added to a new herd, with most sorry results. 



It seems in these cases that an infection which is not capable of 

 producing acute symptoms in one herd of animals may, when car- 

 ried to a distance and introduced into a new herd, have the effect 

 of setting up an outbreak of the most severe nature, with all the 

 symptoms of acute cholera. 



I know of several cases where this very thing has happened. 

 Hogs were purchased which were, to all appearances, in good 

 health. They were taken to new surroundings and placed in the 

 feed lots with other hogs, and one to two weeks later the usual 

 symptoms of cholera began to show up in these new herds. When 

 passed on to the new herd the disease made a most wonderful 

 change, and, instead of being masked by a few doubtful symptoms, 

 showed all the evidence of the real old-fashioned hog-cholera. 



An animal which is suffering from the chronic form of hog- 

 cholera is usually carrying a number of large ulcers in the bowel, 

 and is passing with the manure large amounts of the virus which 

 produces the disease. This virus will attack any healthy hog with 

 which it may come in contact, and when it is introduced into a 

 new herd the type of disease which it produces is often much more 

 severe than that which was present in the animal that spread 

 the infection. 



Carelessness with respect to closely noting the condition of 

 animals that are being added to the herd, and failure to enforce a 

 proper period of quarantine before adding them to the other ani- 

 mals on the place, has often led to most fearful losses. The intro- 

 duction into the herd of a single animal suffering from chronic 

 cholera has often been sufficient to start up an outbreak which 

 will wipe out the entire herd before it can be checked. It is 

 impossible to be too cautious in this respect, and no new animals 

 should be added to a healthy herd unless they are first placed 

 in a separate pen and carefully watched for a period of at least 

 three weeks, and preferably for four weeks, to see that they are 

 absolutely free from disease. This may mean a httle inconvenience 



