Dairy production practices and associated risks for bovine vaccinia exposure in cattle, Brazil

Abstract

A cross-sectional serosurvey was performed to identify environmental features or practices of dairy farms associated with risk for exposure to vaccinia-like viruses in dairy cattle in Brazil. Sera from 103 cows from 18 farms in Minas Gerais state were examined for Orthopoxvirus-neutralizing antibodies. A database of 243 binary or multiple-selection categorical variables regarding the physical features and surrounding ecology of each property was obtained. Thirteen of 46 presumptive predictor variables were found to be significantly associated with Orthopoxvirus serostatus by univariate logistic regression methods. Use of teat sanitizer and having felids on the property were independently associated with virus exposure by multivariable analysis. Rodents have long been suspected of serving as maintenance reservoirs for vaccinia-like viruses in Brazil. Therefore, domestic felids are not only effective predators of small rodent pests, but also their urine can serve as a deterrent to rodent habitation in buildings such as stables and barns. These results corroborate previous evidence of the high significance of rodents in the Vaccinia virus transmission cycle, and they also raise questions regarding the common use of teat sanitizers in dairy production areas.

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

“…Borges and colleagues described a seroprevalence of neutralizing antibodies against OPV in 75.7% of dairy cows sampled in rural communities of Minas Gerais State [ 22 ]. Furthermore, the presence of domestic felids on a property was significantly associated with diminished odds of a cow having OPV-neutralizing antibodies.…”

“…Even during scientific conferences in Brazil and worldwide, questions such as “is there any chance someone could get infected with VACV by drinking milk from infected cows?” have emerged. Indeed, studies focused on the relationship between VACV transmission and dairy production have grown significantly over these 20 years of VACV history in Brazil [ 20 , 21 , 22 ]. Figure 3 displays a timeline with chronological events related to the detection of VACV in dairy products.…”

“…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 ].…”

“…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 ].…”

“…The classic form of VACV transmission is through direct contact between the milkers and infected dairy cows, which characterizes BV as an occupational zoonosis [ 16 ]. Furthermore, the sick dairy workers are often removed from work, which results in disruption of the service in the affected rural properties, as well as additional expenses related to the replacement of human resources and decreases the familiar incomes of these affected milkers [ 13 , 20 , 22 , 23 ]. The following discussion of VACV and BV researches illustrates chronologically how they have become a very important part of virology and epidemiology history in Brazil during the past 20 years.…”