3 BULLETIN 662, U. S. DEPARTMENT OF AGRICULTURE 
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 hverymen, 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 animals in the field rarely show soreness of the feet, 
which is a common symptom of foot-and-mouth disease. Moreover, 
many horses have this particular ailment, but horses have not been 
observed to contract foot-and-mouth disease in any of the previous 
foot-and-mouth outbreaks in the United States. Hundreds of hogs 
exposed to the disease and in association with the sick animals in 
pastures have shown no signs of the malady, which is regarded as 
significant, because in the 1914 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 con- 
secutive days in the mouths of both horses and cattle, and vesicles 
were observed on the bases of tongues whose free portions were al- 
most denuded of mucous membrane as a result of the rupture of 
similar vesicles six or seven days before. 
Complications are extr emely rare in vesicular stomatitis, and 
mammitis and chronic diseases of the hoof following vesicular 
stomatitis, are unusual. 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, but in may cases are, in appearance, indistinguish- 
