December 21, 2016

Temperature as a Factor in Resistance of Young Puppies to Canine Herpesvirus

L. E. Carmichael, Frances D. Barnes and D. H. Percy Source: The Journal of Infectious Diseases, Oxford University Press,1969

This study is trying to determine the effect of temperature on resistance to canine herpesvirus in young Beagle puppies. Studies have found that younger animals are more susceptible to fatal infections of CHV than adult animals. However, studies of growth of CHV in cell cultures indicate that environmental temperature was critical over a narrow range of 2 degrees Celsius. Optimal yields of infectious virus growth were produced at 35-37 degrees Celsius which is below the normal rectal temperature of the mature dog. The prediction then was that artificially changed temperatures above or below the optimal growth range would increase resistance to CHV and slow down the rate of CHV cell growth in young Beagle puppies. 3 litters with a total of 14 puppies were divided into groups, inoculated by the oral nasal route with 0.5ml of viral suspension, and placed into humidified incubators maintained at different temperatures. Pups were fed via a stomach tube with bitch's milk substitute and rectal temperatures were taken 3 times a day using a thermistor probe. Unless an animal had died, or was killed for specimens, pups were maintained in the warmer incubator for 2 weeks and then removed to an incubator kept at 85, most of the puppies died within 10 days of inoculation, the dead dog would then be examined by necropsy. Survival of inoculated newborn puppies was pro- longed, and viral growth was significantly reduced when animals were kept in an environment that elevated their body temperatures to 101.5-103 degrees Fahrenheit. The study concluded that the high susceptibility of newborn pups to fatal CHV infection may be due to their relatively low and poorly regulated body temperatures. The experiment studies Beagle puppies 4 to 8 weeks old and finds poorly regulated body temperatures to be the main factor in determining resistance to CHV infection. The newborn dog is unable to regulate body temperature until the second week of extrauterine life. Since temperature stabilization does not occur in these puppies until about the second week of life, I think the effects of inoculation should be studied during the first two weeks. The should be another study done on the growth rates of viral infection in a variety of animals with naturally varied body temperatures.

Reviewed by Jonathan Guzman