The detection of Vaccinia virus confirms the high circulation of Orthopoxvirus in buffaloes living in geographical isolation, Marajó Island, Brazilian Amazon

•High seropositivity of Orthopoxvirus in buffaloes living in geographical isolation, Brazil.•First molecular characterisation of Vaccinia virus in buffaloes in Brazil.•The geographical isolation might be sine qua non condition to explain high circulation of the Vaccinia virus. In Brazil, serologic evidence of Orthopoxvirus (OPV) circulation showed positivity around 20% in cattle, humans, monkeys and rodents. Although OPV seropositivity has been described in buffalo herds in southeastern Brazil, no Vaccinia virus (VACV) (member of genus OPV) outbreaks in buffalo herds have been described in this country. This study aimed to investigate the detection of anti-OPV antibodies and to study the OPV genome in Brazilian buffalo herds. Our results demonstrated a high OPV seropositivity in buffalo herds on Marajó Island and molecular data confirmed the circulation of VACV. The geographical isolation conditionmight be a sine qua non condition to explain our results.