Long-lasting stability of Vaccinia virus strains in murine feces: implications for virus circulation and environmental maintenance

Vaccinia virus (VACV) has been associated with several bovine vaccinia outbreaks in Brazil, causing exanthematic lesions in dairy cattle and humans. The way that VACV circulates in the environment is unknown, as is the way that this virus is transferred from wildlife to farms. Rodents are hypothetical VACV reservoirs, and murine feces has been identified as a potential source of viral shedding and transmission. In this work, we analyzed the stability of VACV infectious particles and DNA in feces from intranasally infected mice, exposed to environmental temperature and humidity, by titration assays and PCR, respectively. The results showed that VACV infectious particles were still detected at 20 days post-environmental-exposure (d.p.e.), while viral DNA was detected until 60 d.p.e. A gradual decrease in fecal viral load could be detected in all analyzed VACV strains. This work indicates long-lasting stability of VACV in murine feces and reinforces the idea that fecal matter may represent a potential source of circulating virus among rodents.