Elevated Exposure to Influenza a Viruses in Wild Pigs (Sus scrofa), Texas, USA

Detections of highly pathogenic avian influenza viruses in mammals have increased globally, underscoring the need to assess influenza A virus (IAV) exposure in species that bridge wildlife, livestock, and human interfaces. We collected serum from 396 wild pigs (Sus scrofa, hybrids of wild boar and domestic swine) between October 2022 and May 2023 on a cattle ranch in north central Texas, USA, to estimate IAV seroprevalence and identify ecologic correlates of exposure. Using commercial blocking ELISAs and hemagglutination inhibition assays, we report high recent exposure of wild pigs to IAVs (seroprevalence 40%, n=396). Seropositivity was highest in individuals that were female, >2 yr old, sampled during spring (compared with fall or winter), and/or sampled <1.5 km from surface water. Almost half (46.3%, 57/123) of the samples were positive for at least two hemagglutinin clade representatives, and 13.8% (17/123) had titers against both an H1 and an H3 strain. These results indicate a hotspot of IAV circulation in wild pigs in north central Texas and highlight elevated exposure near water bodies, where wild pigs may contact wild waterfowl. Enhanced surveillance of wild pigs at the wildlife-livestock-waterbird interface is warranted to better understand ecologic and epidemiologic pathways for IAV transmission and reassortment.