Serologic and Molecular Evidence of Vaccinia Virus Circulation among Small Mammals from Different Biomes, Brazil

Abstract

Vaccinia virus (VACV) is a zoonotic agent that causes a disease called bovine vaccinia, which is detected mainly in milking cattle and humans in close contact with these animals. Even though many aspects of VACV infection have been described, much is still unknown about its circulation in the environment and its natural hosts/reservoirs. To investigate the presence of Orthopoxvirus antibodies or VACV DNA, we captured small rodents and marsupials in 3 areas of Minas Gerais state, Brazil, and tested their samples in a laboratory. A total of 336 animals were tested; positivity ranged from 18.1% to 25.5% in the 3 studied regions located in different biomes, including the Atlantic Forest and the Cerrado. Analysis of nucleotide sequences indicated co-circulation of VACV groups I and II. Our findings reinforce the possible role played by rodents and marsupials in VACV maintenance and its transmission chain.

Keywords: Brazil; VACV; bovine vaccinia; hosts; marsupials; orthopoxvirus; rodents; vaccinia virus; viral ecology; viruses.

Figure 1

Locations of study areas, Minas Gerais state, Brazil. A) Locations of the 3 municipalities where collections were performed: Sabará, Serro, and Rio Pomba. Inset shows location of Minas Gerais state in southeastern Brazil. B) Identification of 3 sample transects in Sabará. Trail 1 has savannah vegetation, and trails 2 and 3 have Atlantic Forest vegetation. Sources: panel A, Scribble Maps; panel B, T.M.F. de Ázara.

Figure 2

Location of collection sites and biomes represented in each, Minas Gerais state, Brazil. A) Collection site 1 in Serro. B) Collection site 2 in Serro. C) Peridomicile collection areas in Rio Pomba. D) Forest and pasture collection areas in Rio Pomba. E) Example of a forest area where animals were captured. F) Example of peridomicile area. G) Example of pasture area. In panels A–D, circles represent areas where transects for capture were demarcated. Sources: panels A,–D, Google Maps, modified by F.V. Nunes; panels E–G, F.V. Nunes.

Figure 3

Interaction networks for vaccina virus among small mammals in Sabará (A), Serro (B), and Rio Pomba (C) in Minas Gerais state, Brazil. The square represents vaccinia virus. Circles represent small mammal species (labeled). The color in the circles represents the area where mammals were collected. The thickness of lines increases with the number of positive samples from a species. Acokur, Akodon cursor mouse; Akomys, Akodon cf; mystax; Calexp, Calomys expulsus; Calphi, Caluromys philander; Calten, Calomys tener; Cersub, Cerradomys subflavus; Didalb, Didelphis albiventris; Didaur, Didelphis aurita; Mus, Mus musculus; Neclas, Necromys lasiurus; Necsqui, Nectomys squamipes; Olisp, Oligoryzomys sp.; Rattus, Rattus rattus; Triset, Trinomys setosus; VACV, vaccinia virus.