4 BULLETIN 662, U. S. DEPARTMENT OF AGRICULTURE 



dime to a silver dollar, filled with, clear or yellowish serous fluid. 

 These blisters may be isolated, but frequently they coalesce to form 

 a large vesicle. They usually rupture in a very short time, which 

 accounts for their not being recognized at times even in the early 

 stages of the disease. The rupture of the vesicles results in exposing 

 the raw underlying surfaces, which appear as reddened erosions with 

 the grayish-white fragments of the torn mucous membrane of the 

 preexisting vesicles still attached to the irregular borders like a 

 fringe. These erosions may become confluent, varying from the 

 size of a dime to that of the palm of the hand, and may even involve 

 practically the entire upper surface of the tongue in horses. Heal- 

 ing varies, but usually occurs quite rapidly in from 8 to 15 days in 

 uncomplicated cases. 



While these lesions in horses are principally confined to the upper 

 surface of the tongue, they may involve the inner surface of the 

 lips, the angles of the mouth, and the gums. In cattle, on the 

 other hand, the tongue does not appear to be so extensively affected, 

 and lesions may also occur on the hard palate, lips, and gums, some- 

 times extending to the muzzle and around the nostrils. Often the 

 lips of the horse are swollen and itchy, which causes the animal to 

 rub the muzzle against any near-by object. In a very few cases 

 fresh cows have shown similar lesions on the teats when their infected 

 calves have been sucking them, but no feet lesions have been observed 

 in these cases. 



Immediately before or simultaneously with the appearance of 

 the vesicles there is present a moderate rise of temperature, which 

 rapidly subsides. A more or less profuse flow of saliva follows^ 

 which dribbles from the lips and consists of a thin, stringy, or frothy 

 fluid. Not infrequently the presence of salivation is the first indica- 

 tion that the animal is sick. Owing to the painful condition of the 

 mouth at this stage, there is loss of appetite or at least inability 

 to eat, and in horses " gritting" of the teeth is quite frequent, while 

 in cattle " smacking " noises are heard as in foot-and-mouth disease. 

 This sensitiveness as a rule remains for several days, after which 

 healing commences, and it is remarkable to observe how quickly 

 the sick animals will begin to eat even while their tongues are still 

 eroded. Although eating well, they do not regain their original 

 thrifty appearance for some time longer. In dairy cows in addition 

 to shrinkage in flesh there is a noticeable reduction in the normal 

 flow of milk for a few days. 



So far as our observations are concerned, the period of incubation 

 of vesicular stomatitis has varied from 36 hours to 9 days, but the 

 greatest number of cases have occurred in from 2 to 5 days after 

 exposure. 



No losses have been reported from uncomplicated cases of this 

 disease in either horses, mules, or cattle. A certain proportion of 

 horses and mules having vesicular stomatitis also became infected 

 with either influenza or contagious pneumonia, or perhaps both, and 

 some deaths have occurred among such animals. 



CONTAGIOUSNESS 



That the malady is contagious has been definitely shown by the 

 transmission of the disease from sick to healthy animals by inocula- 

 tion. The degree of contagiousness, however, varies between wide 



