INFECTIOUS DISEASES 



303 



ease spreads rapidly, tliroiigli the movement of live-stock affected 

 by the disease. Animals recently recovered may infect other 

 animals. Dogs, birds, people, vehicles, milk, roughage, grains 

 and other material from an infected farm may spread the disease. 



The period of incuhation is sliort. Symptoms of disease may 

 be manifested in from one to six days following exposure. 



The first symptoms are fever, dulness, trembling and loss of 

 appetite. This is followed by vesicles or blisters forming on the 



Fig. 106. — A cow affected with foot-and-mouth disease. Note the accumulation of saliva 

 about the lips. (From report of the Bureau of Animal Industry.) 



mucous membrane of the mouth, lips, between and above the 

 claws and the region of the udder. The inflammation of the 

 mouth and feet may be very painful. Long strings of saliva 

 may dribble from the mouth and collect about the lips (Fig. lOG). 

 A smacking or " clucking " sound is produced when the animal 

 moves its jaws and lips. The severe pain resulting from the 

 inflammation of the mouth and feet, and the difficulty in moving 

 about and eating and drinking, cause the animal to lose flesh and 

 become emaciated. Milk cows may go dry. 



The death-rate is not heavy. Some writers place it as low 



