Avaliação dos fatores de exposição ao Vaccinia virus (VACV) em diferentes populações do Brasil

Abstract

The family Poxviridae comprises large and complex animal viruses with DNA genome which have the peculiarity to multiply in the cytoplasm of host cells. Orthopoxvirus (OPV) is one of the genera and among their representatives we can highlight Cowpox virus (CPXV), Monkeypox virus (MPXV), Variola virus (VARV) and Vaccinia virus (VACV). The incidence of zoonotic OPV infections have increased in recent years and these findings can be directly related to cessation of smallpox vaccination after its eradication. VACV is the agent of bovine vaccinia (BV) in Brazil, associated with ulcerative lesions in cattle and milkers, resulting in economic losses, and social and public health impacts. Since 1999, several BV outbreaks have been reported in the country and a large number of viral strains were isolated and characterized. The aim of this study was to evaluate the occurrence of previous VACV infections and its dispersion in a vulnerable population of an important dairy region of Minas Gerais State, also identifying exposure factors. During August 2012 to March 2013, an epidemiological survey was conducted among individuals living in rural areas of Serro city and collected 240 serum samples. To assess immunity it was performed plaque reduction neutralizing test. The studied population comprise 127 men (52.9%) and 113 women (47.1%), aged between 5 and 90 years. Most participants have brown skin color (59.2%) and also have a minimum monthly income (72.4%). Twenty-four people (10%) reported not having study and 156 (65%) attended for 8 years. About occupation, 127 (52.5%) are rural workers, 59 women (24.6%) reported working only in home environment and 54 (22.5%) have no profession directly related to rural environment. It was found that 74 participants (30.1%) have anti-OPV neutralizing antibodies with titers ranging from 100 to 12.800 neutralizing units per ml. Exposure factors analyzed, contact with cattle and horses, vaccination history, vaccine take presence, participation in cheese production and milking practice were statistically significant when compared with presence of neutralizing antibodies (p < 0,05). Furthermore, it was detected lesions similar those observed during BV outbreaks in one participant, and viral DNA in 5 of them. This finding features a VACV household transmission case, which is hardly reported in outbreaks. During the campaign for smallpox eradication, it was thought that immunity against OPV would be long lasting. However, VACV outbreaks affecting vaccinated people have been reported in Brazil. As shown in this study, there is a significant prevalence of anti-OPV antibodies in no vaccinated individuals (without vaccine take). These data are similar to studies conducted in other countries, where there is occurrence of other poxviruses as CPXV and MPXV. This suggests an active circulation of OPV in areas where individuals are directly exposed due to their work activities.