Experimental Virus Infections in Chinese Hamster. II. Susceptibility to Street Rabies Virus

It has been noted 1 that the Chinese hamster is susceptible to fixed rabies virus, but its susceptibility to street rabies virus still remains to be determined. Observations on its behavior to infection by a strain of street rabies virus are, therefore, described here.

A fresh local strain of street rabies virus from dog was used in the present study. The original virus preserved in 50% glycerine was thoroughly ground in a sterile mortar and suspended in saline solution for inoculation. Chinese hamsters weighing 20-30 gm. were divided into several groups and each was separately inoculated with various dilutions of the dog brain virus through different routes as indicated in the table. The technique of inoculation was similar to that used previously. 1 The records of observations made on the incubation period, mortality, and days of death in relation to routes of inoculation and concentration of virus introduced are summarized in Table I.

Ten to 20 days after inoculation with the virus, the infected animals began to show increased excitability, which became very pronounced within 24 hours after its first appearance. The animals generally ran about constantly and bit the wire mesh of the cage. The movements of the body were shaky and unsteady. Fits of convulsion, especially when the animals were irritated, soon followed. Feedings were poorly taken and emaciation became noticeable. After 2 or 3 days of excitement, weakness or paralysis of the hind legs usually could be noted. In some animals, however, paralysis was observed to start from the front limbs. The animals usually died in 2 to 5 days after showing the first symptoms of excitement. When the course is acute as in animals inoculated intracerebrally with high concentration (1:400) of the virus suspension, death may result in 2-3 days after development of excitement without showing weakness of limbs.

The effectiveness of administration of the virus through different routes decreased in the following order: intracerebral, intramuscular, subcutaneous, and intraperitoneal. The first route was by far the most effective as fatal infection resulted with inoculation of virus suspension diluted as high as 1 to 1,000,000. The incubation time and day of death varied with two factors, namely the concentration of virus suspension and route of its introduction. When concentrated virus suspension was given, the incubation time and day of death tended to be shortened. They were also shortest when virus was introduced intracerebrally but were lengthened by 2 to 12 days when virus was introduced through other routes.