Evidence supporting wild boar as reservoir host species for influenza

A total of 727 wild boar sera were collected during the hunting season (October to December) in Southern Belgium. The sampling was conceived to cover as much as possible the whole territory, with respect to the known local... [ view full abstract ]

A total of 727 wild boar sera were collected during the hunting season (October to December) in Southern Belgium. The sampling was conceived to cover as much as possible the whole territory, with respect to the known local wild boar densities. Presence of influenza A virus anti-nucleoprotein antibodies was measured using the ID Screen® Influenza A Antibody Competition ELISA kit (Id_Vet, France), according to the manufacturer’s instructions. Positive and doubtful results were further submitted to standard hemagglutination inhibition assay (HIA), using the strains A/Sw/Belgium/1/98 (H1N1), A/Sw/Flanders/1/98 (H3N2) and A/Sw/Gent/7625/99 (H1N2). To estimate effects of potential factors (sex, age, month, province, hunting territory, wild boar, domestic pig and pig farm densities) on risk for seropositivity, we used a multivariate logistic regression model. Between-group differences were assessed by using the χ2 test. Taken together, our results demonstrate the existence of a stable circulation of H1N1 influenza virus in some of the sampled wild boar populations, which suggests that wild boars act as a reservoir in the epidemiology of influenza viruses. Virological studies aimed at isolating the strains circulating in forest blocks with high seroprevalence will be undertaken to assess the origin and possible evolution of these strains.