SOME COMMUNICABLE DISEASES . 359 



Symptoms. — In three to six days after exposure, the following 

 symptoms appear: a moderate fever; the eruption of small 

 blisters containing a straw-colored fluid in the mouth, between 

 the claws of the feet, and in severe cases on the udder and teats. 

 After the disease becomes well established, the lesions in the 

 mouth make eating difficult and stimulate a profuse flow of 

 saliva, which hangs from the lips in strings (Fig. 90). When the 

 f eeft are severely affected, the animal lies down much of the time. 

 Caked udder and abortion are secondary, or complicating, 

 diseases that reduce the productivity to such an extent that the 

 losses may amount to 20 or 30 per cent, of the value of affected 

 cows. In hogs the lesions are largely confined to the feet so 

 lameness is the most prominent symptom in these animals. An 

 early diagnosis is especially necessary in the first cases of an. 

 outbreak in order to bring the disease under control. The 

 method usually followed is the inoculation of calves with fluid 

 from the small blisters of supposedly infected animals. 



Treatment. — In the United States no attempt is made to 

 treat animals known to be affected with or exposed to foot-and- 

 mouth disease. Instead, they are slaughtered and their bodies 

 disposed of under the direction of the live stock sanitary authori- 

 ties. This method of handling outbreaks has been successful 

 in stamping out the disease every time it has appeared. The 

 last outbreak, which occurred in 1914, was widespread but was 

 prevented from getting a permanent foothold in this country by 

 the method of control just described. An attempt has been 

 made to produce a serum for immunizing cattle, but results from 

 its use do not appear to have been satisfactory. 



FOOT ROT 



Cattle and sheep occasionally suffer from a contagious foot rot. 

 Unless steps are taken to control the disease, it may spread to 

 many animals in the herd or flock and result in death from absorp- 

 tion of toxic products. 



Cause. — The organism responsible for most outbreaks of 

 foot rot is the Bacillus necrophorus, the same germ that causes 

 necrobacillosis of pigs. 



Symptoms. — Affected animals become lame, develop a hot 

 and painful swelling around the hoof, lose their appetite, get 



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