Highly pathogenic avian influenza H5 virus exposure in goats and sheep

The recent outbreaks of highly pathogenic avian influenza A(H5N1) virus in North and South America, including widespread infection of cattle in the United States, calls for an urgent assessment of the host range of influenza A viruses, particularly for subtypes of pandemic concern. We conducted a serological survey for binding antibodies to influenza A and B viruses in goats (n=452) and sheep (n=329) in Pakistan and found high seropositive rates for the hemagglutinin (HA) of avian influenza A viruses (AIV) H5 (23.9–34.0%), H7 (13.9– 37.1%), and H9 (17.0–34.7%). In contrast, there were low levels of seropositivity against the HA of human and swine pandemic H1N1/pdm09 (0.9–1.8%) in goats and against swine H3 (0.6%) in sheep. Notably, we observed high reactivity to the neuraminidase of human H1N1/2009 (57.8–60.6%) and swine H3N2 (14.0–14.4%), likely due to cross-reactivity with the N1 and N2 proteins of H5N1 and H9N2 AIVs, respectively. Interestingly, we also detected seropositivity against influenza B HA in both goats (7.1%) and sheep (4.6%). The presence of AIV antibodies in goats and sheep suggest these species represent previously unrecognized hosts for viruses of pandemic concern, revealing extensive gaps in our current understanding of the ecology of influenza A and B viruses.