Short communication: Parapoxvirus and Orthopoxvirus coinfection in milk of naturally infected cows

Abstract

Several studies have shown the occurrence of poxvirus infections associated with exanthematic lesions in cattle from many Brazilian states. Coinfection between viruses belonging to 2 genera, Orthopoxvirus (OPXV) and Parapoxvirus (PPV), was already identified from the lesions of affected cows and humans. The DNA and infectious viral particles of Vaccinia virus, an OPXV, have been detected in milk of naturally and experimentally infected cows. However, to date no reports have described the detection of Pseudocowpox virus, a PPV, in milk. Thus, we investigated the presence of PPV and OPXV in milk samples obtained from dairy cows from a Brazilian region with exanthematic disease outbreaks. From 2011 to 2014, 6 dairy farms with exanthematic disease outbreaks involving dairy cows, calves, and humans were visited. Twelve crusts of cows' teat lesions and 60 milk samples were collected. The crusts and milk samples were analyzed by PCR to detect OPXV or PPV DNA. According to the analyzed crusts, we detected PPV infection in 4 of the 6 visited farms, from which we investigated the PPV contamination in milk. From the 40 milk samples tested, PPV DNA was detected in 12 samples. Of these milk samples, 8 were positive for both PPV and OPXV. This is the first report of PPV DNA detection in milk samples from affected cows, indicating that the virus may be present in milk and potentially contaminating dairy products associated or not with OPXV. In addition to the lesions caused by direct contact, the presence of 2 or more poxvirus species in milk showed that the effect of zoonotic exanthematic diseases on public health and animal husbandry is relevant and cannot be overlooked.

Keywords: Orthopoxvirus; Parapoxvirus; coinfection; milk.