SYMPTOMS OF FOOT AND MOUTH DISEASE 205 



of animals in a short period of time. Very little immunity is 

 produced by foot and mouth disease, repeated attacks having 

 been known to occur in the same animals. 



Foot and mouth disease has appeared in the United States 

 on six different occasions. The recent outbreak of 191-i was 

 by far the most serious as well as the most extensive that has 

 ever occurred in this country. All of the previous outbreaks 

 were quickly and successfully eradicated. 



Cause. — The causative factor of foot and mouth disease has 

 never been isolated or identified, although numerous attempts 

 have been made to discove*- the specific organism. The virus or 

 the disease-producing material may be found in the blisters on 

 the mouth, feet, udder and in the saliva, milk and various secre- 

 tions and excretions, and in the blood, during the time when the 

 temperature is high. Animals may become infected directly by 

 licking, and in calves by sucking, or indirectly by infected hay, 

 manure, drinking troughs, railway cars, stock-yards, barn-yards, 

 and pastures. The time elapsing between the exposure of an 

 animal to infection and the development of the disease in that 

 animal varies usually from three to six days. The disease may 

 appear in twenty-four hours, again in exceptional cases, not for 

 eighteen days or longer. 



Symptoms. — In foot and mouth disease the early symptoms 

 consist of spells of shivering or chilling, quickly followed by 

 fever, causing the body to become exceedingly warm. The body 

 temperature may be as high as 105 or 106 degrees F. These 

 symptoms do not always occur, or may be in so mild a form as to 

 escape notice. Following this in one or two days, small vesicles 

 or blisters about the size of a pea will make their appearance 

 upon the mucous membrane of the mouth and tongue or on the 

 lips or the margin of the dental pad. These small blisters are 

 filled with a yellowish watery fluid and become more extensive 

 as the disease progresses. Shortly after the eruptions have 

 appeared in the mouth (Fig. 71), it will be noticed that there is 

 considerable swelling and redness shown about the feet in the 

 region of the coronet and between the toes. The formation of 



