Detection of Vaccinia Virus in Milk: Evidence of a Systemic and Persistent Infection in Experimentally Infected Cows.

Bovine vaccinia (BV) is a zoonosis caused by Vaccinia virus (VACV), which affects lactating cows and milkers. VACV DNA and infectious particles have been detected in milk of naturally infected cows. However, the period and pattern of VACV shedding in milk is unknown, as is whether the presence of VACV in milk is due to a localized or a systemic infection. To address those questions, eight lactating cows were inoculated with VACV in previously scarified teats. The experiment was divided in two phases. In Phase 1, milk samples were collected daily for 33 days, and in Phase 2, four animals from the first phase were immunosuppressed. In both phases, milk was collected with a sterile catheter on even days and by hand milking on odd days. All animals showed typical BV lesions in the inoculated teats. All milk samples were subjected to nested polymerase chain reaction (PCR) and real-time quantitative PCR to detect VACV DNA. PCR-positive samples were subjected to virus isolation. VACV DNA was intermittently detected in milk in both phases and infectious viral particles could be detected only in phase 2, on the 69th, 73rd, 74th, 77th, 79th, and 81st days postinfection. Despite the possibility of propagation of VACV through milk, it is known that milk continues to be drawn and marketed normally during outbreaks of the disease. The detection of both VACV DNA and infectious particles in milk samples draws attention to the potential public health risk associated with the consumption of milk from BV outbreaks. Detection of VACV in the milk from noninfected teats demonstrated that VACV shedding in milk might be related to a systemic infection. Moreover, it was shown that VACV DNA and viral infectious particles could be detected in milk even after healing of the lesions, demonstrating that VACV may cause a persistent infection in cattle.

Susceptibility of Vaccinia virus to chemical disinfectants.

Vaccinia virus (VACV) is the cause of bovine vaccinia (BV), an emerging zoonotic disease that affects dairy cows and milkers. Some chemical disinfectants have been used on farms affected by BV to disinfect cow teats and milkers' hands. To date, there is no information about the efficacy of disinfectants against VACV. Therefore, this study aimed to assess the virucidal activity of some active disinfectants commonly used in the field. Sodium hypochlorite, quaternary ammonium combined with chlorhexidine, and quaternary ammonium combined with glutaraldehyde were effective in inactivating the virus at all concentrations tested. Iodine and quaternary ammonium as the only active component were partially effective. The presence of bovine feces as organic matter and light decreased the effectiveness of sodium hypochlorite. These results show that an appropriated disinfection and asepsis of teats and hands may be helpful in the control and prevention of BV and other infections with VACV.