Differential Susceptibility to a Viral Agent in Mice Housed Alone or in Groups

Abstract

In two strains of mice, individually housed animals were more susceptible to encephalomyocarditis (EMC) virus than those housed in groups. Increasing the size of the group from 5 to 20 mice/cage did not further alter resistance. Attempts were made to delineate the physiologic mechanism(s) responsible for the differential susceptibility to EMC virus. Body weight and body temperature prior to injection did not differ in individually and group-housed mice. Interferon and antibody levels following inoculation with EMC virus did not explain the observed differences in mortality, nor did the antibody levels observed in response to an inactivated EMC virus vaccine. Corticosterone levels at the peak of the adrenocortical rhythm were noted to be higher in mice housed individually than in those housed 5/cage, and this difference was noted both prior to and following EMC inoculation.