6 BULLETIN 662, U. S. DEPARTMENT OF AGRICULTURE. 



ment animals for inoculation, and also of injecting the infectious 

 material as soon as possible after the blisters have formed. 



The virus is evidently of short life, and is transmitted only by close 

 contact. Probably the infected environment remains dangerous 

 longer than the affected animals. At the Bureau of Animal Industry 

 Experiment Station one field was set aside for animals which had 

 recovered from attacks of vesicular stomatitis. Horses and cattle 

 were placed in this field 3 weeks after they first showed symptoms of 

 the disease. Healthy susceptible cattle were kept in this field as 

 a check on the possible spread of the disease, but in no instance did 

 they become infected. Likewise, susceptible animals turned into a 

 stable which 3 weeks previously in one instance, and 16 days pre- 

 viously in another instance, had harbored active cases of vesicular 

 stomatitis, remained well. Several instances have been reported in 

 which a line fence or a board fence in a double corral has been suffi- 

 cient to prevent transmission of the disease from the infected animals 

 on one side to the healthy animals on the other. 



Investigations indicate that the disease is very seldom communi- 

 cated by owners or caretakers of affected animals visiting other 

 farms. As a rule the disease appears to spread by direct contact with 

 recently affected animals, or by recently infected feed troughs, water 

 troughs, bridles, or pails. Inoculation experiments on such labora- 

 tory animals as rabbits, guinea pigs, rats, and mice have resulted 

 negatively. The disease manifests itself in susceptible animals 

 more rapidly after the application of infectious material to scarified 

 areas in the mouth than through intravenous injection, although 

 positive results have been obtained also by the latter method. 



Contrary to experiences in the field, we were able in several test 

 inoculations to transmit infection to the feet of cattle in a small pro- 

 portion of cases, and likewise this virulent material also produced 

 lesions in from five to nine days in the feet of one hog, in the mouth 

 of another, and on the snout of the third. While these cases were 

 the exception and not the rule, they should be recorded for their 

 scientific interest. In this comiection it should be stated also that a 

 number of hogs in immediate contact with these animals but with- 

 out receiving any artificial inoculation remained normal in all cases, 

 while a number of cattle similarly exposed contracted lesions which 

 were confined solely to the mouth. Infectious material expelled 

 from the mouths of attacked animals and kept moist by placing it in 

 a sealed test tube, protected against exposure to light, retained its 

 virulence for three weeks in one instance. Such material after being 

 dried or preserved in normal salt solution lost its virulence in a much 

 shorter period of time. 



Very little work appears to have been done on the question of 

 immunity in this disease. A number of horses and cattle which were 



