Mousepox in inbred mice innately resistant or susceptible to lethal infection with ectromelia virus. IV. Studies with the Moscow strain.

The pathogenesis and transmission of infection with the Moscow strain of ectromelia virus were studied in inbred mice. BALB/cAnNcr had high morbidity and mortality and C57BL/6Ncr (B6) mice had high morbidity and low mortality. Virus was detected in B6 mice for 2 weeks after subcutaneous (s.c.) inoculation and infected mice developed lesions compatible with acute mousepox. B6 inoculated by footpad transmitted infection to cagemates for up to five weeks and soiled cages that had housed infected mice were infectious for three weeks. S.c.-inoculated B6 mice also transmitted by contact for 2 weeks. Transmission was attributed to oronasal excretion of virus. Airborne transmission of infection between adjacent cages occurred at a low rate. Ectromelia virus-free progeny were derived from previously infected dams. These studies indicate that the highly virulent and infectious Moscow strain of ectromelia virus caused self-limiting infection in inbred mice and that direct contact is the most efficient means of transmission. These findings support the concept that mousepox can be contained by husbandry practices that minimize or eliminate the spread of infection by direct contact or fomites.