6 BULLETIN 662, U. S. DEPARTMENT OF AGRICULTURE 



scientific interest. In this connection 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 

 typically affected at the bureau experiment station failed to contract 

 the disease when inoculated with the virus three months later, 

 although the control animals became infected promptly. It may be 

 stated that in these cases immunity had persisted for at least three 

 months. Further tests regarding its duration could not be made, 

 because the required infectious material was not obtainable owing to 

 the disease having disappeared. Injections of blood serum from 

 immune animals so far as tested induced no resistance to the disease. 



Whether the milk of affected cattle is or is not infectious for 

 people has not been recorded, but such milk has been fed experi- 

 mentally to hogs without producing any ill effects. 



DIFFERENTIAL DIAGNOSIS 



While the disease has not the great economic importance of foot- 

 and-mouth disease, it nevertheless is contagious and causes consider- 

 able alarm owing to its close resemblance to the dreaded European 

 disease. Furthermore, as most writers state, this infection in cattle 

 may be readily confounded with foot-and-mouth disease, and experi- 

 ence has shown that a prompt and exact differentiation is accom- 

 panied with numerous difficulties. The real difficulties surrounding 

 the diagnosis are best appreciated by those who have faced them with 

 the consciousness that their pronouncement if mistaken would lead 

 on one hand to unnecessary and serious economic disturbances and on 

 the other hand to the spread of one of the most dreaded and easily 

 communicated among animal plagues. Vesicular stomatitis there- 

 fore will prove a menace whenever and wherever it may reappear. 

 For these reasons it is strongly urged that local quarantines to pre- 

 vent its spread be imposed by State livestock officials in whose terri- 

 tory the disease may be found. All owners and handlers of horses, 

 mules, and cattle, particularly liverymen, managers of stockyards, 

 and stockmen, should be directed to separate sick from well animals, 

 clean and disinfect contaminated premises, and have all infected 

 animals appropriately treated. 



The opinion that the malady is not foot-and-mouth disease is based 

 on the fact that persistent observation of sick animals has failed to 

 reveal certain typical symptoms which would be expected in an out- 

 break of foot-and-mouth disease. The drooling, vesicles, and ero- 

 sions are similar in appearance to those produced by foot-and-mouth 

 disease, but in none of the animals examined in the field has there 

 been found any soreness of the feet, which is a common symptom 

 of foot-and-mouth disease. Moreover, many horses have this par- 



