The adverse effect of environment on the response to distemper vaccination.

Three standard batches of combined distemper and hepatitis vaccine tested in pups housed indoors during a constantly hot summer failed to elicit antibody to distemper virus or to protect the pups against challenge with virulent virus. The response to hepatitis vaccination was normal. When tested in pups housed outdoors, the same batches of vaccine produced antibodies to distemper and protection against the disease. It appears that high relative humidity combined with high environmental temperature caused an increase in body temperature of the pups which was deleterious to the distemper vaccine but did not affect the more heat resistant hepatitis vaccine.