Vaccinia virusdetection in dairy products made with milk from experimentally infected cows

Abstract

Summary Vaccinia virus (VACV) is the agent of bovine vaccinia (BV), an emerging zoonosis that causes exanthematic lesions on the teats of dairy cows and on the hands of milkers. The virus has been detected in the milk of naturally infected cows. The objective of this study was to investigate and quantify VACV DNA as well as the presence of infectious virus particles in samples of cheese curd, cheese whey and pasteurized milk produced using milk from cows experimentally inoculated with VACV‐GP2, a Brazilian isolate of VACV (VACV‐BR). VACV DNA was detected in samples of cheese and pasteurized milk at different time points, even after the resolution of the typical lesions caused by VACV, which occurred after 22 days post‐infection (dpi), on average. Moreover, it was possible to detect infectious viral particles in cheese samples on alternate days until 27 dpi. The presence of both VACV DNA and infectious viral particles in cheese samples throughout the clinical course of BV and even after the disappearance of the typical clinical signs of disease draws attention to the risk associated with consumption of the cheese. Furthermore, VACV‐contaminated milk and cheese may represent an occupational risk to cheesemakers who often manipulate milk and cheese curd without wearing gloves.

Twenty Years after Bovine Vaccinia in Brazil: Where We Are and Where Are We Going?

“…In the following years, other correlated researches would appear, revealing that VACV viral particles could not be inactivated even after thermal treatments of milk and during cheese processing, both in their production and in their maturation period. The detection of infectious viral particles (from both groups I and II) in milk samples and dairy products confirmed this hypothesis [ 80 , 81 , 82 , 83 , 84 ].…”

“…It is noteworthy that serological and molecular evidence was detected in naturally and experimentally infected cows, and dairy products produced from the milk of these animals, raising the discussion about the persistence of systemic infection in these animals [ 13 , 84 ]. In addition to this evidence, Borges et al demonstrated that even in rural properties with no record of BV outbreaks, dairy cattle could present neutralizing antibodies against VACV [ 22 ].…”

“…Furthermore, the practice of milking without properly sanitizing cows’ udders can directly affect cattle exposure and milkers [ 22 ]. All the studies conducted over the past few years reinforce the possibility that dairy products could work as vehicles for VACV dissemination and potential risks generated to public health [ 78 , 80 , 81 , 82 , 83 , 84 ].…”

An Update on the Known Host Range of the Brazilian Vaccinia Virus: An Outbreak in Buffalo Calves

“…In addition, a study on the ingestion of contaminated milk by mice demonstrated systemic infection in the absence of clinical signs (Rehfeld et al, 2015). Reinforcing this possible route of infection, viable VACV has been detected in artisanal cheese samples produced with the milk of experimentally infected dairy cows (de Oliveira et al, 2018). We suggest that similar circumstances might be evident with dairy products derived from water buffaloes.…”

Bovine Vaccinia: Insights into the Disease in Cattle

“…Studies of experimentally contaminated milk and artisanal cheeses produced with this milk have demonstrated the viability of VACV after a heat treatment at 65 °C, as well as in artisanal cheese and milk stored at low temperatures [ 76 ]. Moreover, viable VACV has been detected in artisanal cheese samples produced with raw milk from experimentally infected dairy cows [ 77 ]. Considering that the virus is secreted via the milk and that it remains viable during the cheese production process, our group analyzed the impact of the ripening process on the viability of VACV in artisanal cheeses [ 78 ].…”