Susceptibility of the Gray Fox to Fox Encephalitis

Abstract

When gray foxes were inoculated intraocularly, intracerebrally and intraperit., they were shown to be relatively resistant to fox encephalitis virus virulent for red foxes. It appears that the virus will regularly infect the gray fox to produce a symptomless infection, but only occasionally will symptoms appear that resemble the disease in red foxes. A virulence gradient of this virus for related spp. can be postulated whereby in the family Canidae the closely related dogs and coyotes (Canis) and the red foxes (Vulpes) are most susceptible, the more distantly related gray fox (Urocyon) less susceptible, and those spp. which are earlier offshoots of the canines, such as the black bear and the raccoon, are the least susceptible to fox encephalitis.