Virulent Canine Distemper Virus Research Articles

Age-Related Susceptibility to Infection with Canine Distemper Virus in Gnotobiotic Dogs

The influence of age on the susceptibility of gnotobiotic dogs to infection with virulent canine distemper virus (R252-CDV) was studied. Of the dogs infected at less than one week of age, 85% died of acute encephalitis two to five weeks after infection. In contrast, only 28.5% of infected weanling and 33.3% of infected adult dogs died after receiving inoculations of R252-CDV. Furthermore, about one-half of the fatally infected weanling dogs developed chronic encephalitis characterized by infiltration of lymphocytes and plasma cells in areas where demyelination of the central nervous system had occurred. Age-related susceptibility correlated with in vitro responses of peripheral blood lymphocytes to phytomitogens. The results of this study suggest that physiological immaturity of the immune system of neonatal dogs may account for their increased susceptibility to infection with CDV.

The virus of canine distemper in cell culture: II. Effect of serial passage in ferret kidney cell cultures and BS-C-1 cell cultures on the virulence of canine distemper virus

Passage of virulent canine distemper virus in ferret kidney cell culture produced little attenuation for ferrets. Virus passaged 8 times in BS-C-1 cell, although producing clinical signs of distemper did not kill 3 3 ferrets. After 21 serial passages in BS-C-1 cells, the virus was modified so that it failed to produce distemper in 8 8 ferrets and only a mild temperature response in 5 5 puppies. Furthermore, the animals were protected against challenge with virulent CDV which killed 10 10 ferrets and produced clinical distemper in 7 7 puppies. These results are highly significant. The BS-C-1 adapted CDV was retested after it had been purified twice by cloning under agar overlay, and at the 37th passage level protected dogs and ferrets. About 10 infective doses of attenuated virus induced active immunity in ferrets: a thousand times this dose produced no signs of clinical distemper in ferrets, and only a mild temperature response in dogs.

A study of the relationship between canine distemper and measles in the dog.

Dogs inoculated with live measles virus readily developed neutralizing and complement-fixing antibodies to measles. The dogs showed no signs of illness and did not spread the infection to unit contact litter mates. Following measles inoculation, 7 of 11 dogs developed low titers of canine distemper neutralizing antibody. All measles-inoculated dogs, including those with no demonstrable canine distemper neutralizing antibody, were protected against intravenous or intracerebral challenge with virulent canine distemper virus, while the contact controls, not receiving measles virus, became ill, and some died. The dogs which had received distemper virus alone developed distemper neutralizing antibody, but developed no measles neutralizing antibody.