First evidence of bovine viral diarrhea virus infection in wild boars

Abstract

Background: The farming of wild boars has growing due to the interest of the human consumption of this exotic meat. Such a development may pose an increased risk of disease transmission between boars and domestic animals. The wild boar population has increased in South America in the last years due the absence of predator causing economic losses due to direct damage to crops and risk of disease transmission. The genus Pestivirus within the family Flaviviridae are composed by four recognized species by the International Committee on the Taxonomy of Viruses (ICTV): classical swine fever virus (CSFV), border disease virus (BDV), bovine viral diarrhea virus type 1 (BVDV-1) and 2 (BVDV-2). Other putative species denoted as atypical pesitiviruses have been reported as 'HoBi'-like virus, giraffe pestivirus, Bungowannah pestivirus, Pronghorn antelope virus, atypical porcine pestivirus (APPV), Norwegian rat pestivirus (NrPV) and Rhinolophus affinis bat pestivirus (RaPestV-1). CSFV is commonly detected in wild boars, but despite positive serology, bovine viral diarrhea virus (BVDV) was never detected in this animal species. Thereby, the present communication describes the first detection of BVDV in the lungs of captive boars using RT-PCR and DNA sequencing. Materials, Methods & Results: Forty lung samples from farmed wild boars were collected after slaughter in a commercial abattoir. The organs were crushed separately, centrifuged, and the supernatant was stored for further analysis. The total RNA was isolated using a phenol-based protocol and RT-PCR protocol that amplified 118 bp of 5' untranslated region (5'UTR) was carried out. One out 40 samples resulted positive. The positive sample had partial fragments of 5'UTR and N terminal autoprotease (Npro) sequenced and analyzed. The strain LV Java/2012 presented 99% of identity in 5'UTR and 98% in Npro region with a BVDV-2 previously reported in bovines in Southern Brazil. In both 5'UTR and Npro phylogenetic analysis, the strain LV Java/2015 clustered with BVDV-2 strains and was most closely related to subtype 2b identified in bovines in Southern Brazil grouping in the same terminal node. Discussion: Wild boars are commonly associated to pathogen transmission to domestic animals. This animal species is considered a reservoir of the pestivirus CSFV and important keys in CSFV control and eradication programs in Europe. Despite indirect presence of BVDV was reported in wild boars by serology tests, the direct detection of the viral agent was never reported. The present study showed the presence of BVDV-2 genomic segments obtained by RT-PCR followed by DNA sequencing in captive wild boars. The reported data suggests a possible importance of this animal species in the epidemiology of ruminant pestiviruses which could interfere in control and eradication programs of these important pathogens for cattle worldwide. The strain LV Java/2012 was closely related to BVDV-2b and presented highest identity with a strain detected in cattle from Southern Brazil. This data suggests that wild boars and bovines could be sharing this pathogen due the similarity of the strains and that both were reported in the same region. It can lead to need of inclusion of wild swines in BVDV control programs since boars can circulate between different regions and carry this pathogen to different cattle herds. The present study reported the first molecular evidence of BVDV in wild boars in the literature. The data generated herein suggests a possible importance of boars in the epidemiology of ruminant pestiviruses.