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



and in association with the sick animals in pastures have shown no 

 signs of the malady, which is regarded as significant, because in 

 the last outbreak of foot-and-mouth disease hogs were as susceptible 

 to that disease as were cattle. Exposed sheep also failed to show 

 vesicular stomatitis, yet these cloven-footed animals are susceptible 

 to foot-and-mouth infection. In a number of cases of vesicular 

 stomatitis the lesions appeared to be continuous or progressive, and 

 not explosive, as in foot-and-mouth disease. In these instances 

 secondary lesions were apparent on a number of consecutive days in 

 the mouths of both horses and cattle, and vesicles were observed on 

 the bases of tongues whose free portions were almost denuded of 

 mucous membrane as a result of the rupture of similar vesicles six 

 or seven days before. 



Complications are extremely rare in vesicular stomatitis, and 

 neither mammitis nor chronic diseases of the hoof have been 

 observed following it. Sucking calves are seldom affected with 

 the disease, and rarely in other than a mild form, while an attack 

 of foot-and-mouth disease in calves is always serious and not infre- 

 quently fatal. The vesicles in foot-and-mouth disease as a rule 

 are larger than in vesicular stomatitis, and are more tightly filled 

 with serous fluid. Furthermore, instead of increasing in virulence 

 by passage through a series of calves, as foot-and-mouth disease 

 has always done in our previous experiments, vesicular stomatitis 

 became greatly reduced in pathogenesis and required a constantly 

 increasing period of incubation before manifesting lesions of the 

 disease. Although numerous filtrate experiments have been con- 

 ducted, in no case has the disease been reproduced in this manner, 

 which is also unlike our experiments with foot-and-mouth disease. 



The percentage of animals infected in each of the herds of cattle, 

 and the history of exposure without transmission of the disease 

 except by immediate contact, would indicate that this ailment 

 is not the highly contagious foot-and-mouth disease which, once 

 it is introduced into a herd, quickly affects practically 100 per 

 cent of the cattle and hogs on all the farms to which the virus may 

 be carried by intermediate agencies. 



The result of this study of vesicular stomatitis suggests tho ne- 

 cessity of inoculating horses with suspected material in any future 

 outbreak of disease bearing a resemblance to foot-and-mouth disease. 



Finally, it must be apparent that in vesicular stomatitis we 

 have a disease more closely resembling foot-and-mouth disease 

 than either mycotic or necrotic stomatitis, and that Hutyra and 

 Marek are correct in their opinion that a reliable differential diag- 

 nosis can be made only after inoculation experiments and careful 

 observation lasting a number of days. 



