Serological evidence of the infection of H7 virus and the co-infection of H7 and H9 viruses in farmed fur–bearing animals in eastern China

Avian influenza virus (AIV) usually infects wild birds and domestic poultry; however, this virus could be transmitted to mammals and humans. The previous studies reported that the farmed mink could be infected with the H5 AIV and H9 AIV, indicating that the farmed fur–bearing animals may be susceptible to AIV. Here, we report the serological evidence of infection of H7 AIV and co-infection of H7 and H9 AIV in healthy framed fur–bearing animals. We collected serum specimens from healthy farmed fur–bearing animals (farmed mink and farmed fox) and make an investigation of serological surveillance of clade 2.3.2 H5 AIV, clade 7.2 H5 AIV, clade 2.3.4.4 H5 AIV, H7 AIV, and H9 AIV. We did not find the hemagglutination inhibition (HI) antibodies against clade 2.3.2 H5 AIV, clade 7.2 H5 AIV, or clade 2.3.4.4 H5 AIV in the serum specimens of farmed fur–bearing animals. However, we found that both farmed mink and farmed fox possess HI antibodies against H7 AIV or H9 AIV; furthermore, we found that some serum specimens possess both anti-H7 AIV antibodies and anti-H9 AIV HI antibodies, suggesting that one farmed fur–bearing animal can be infected with two different subtype AIVs and may play an important role in the reassortment course of the novel avian influenza viruses. Taken together, our data suggested that the enhanced surveillance of AIV in farmed fur–bearing animals and humans or animals in close contact with them is needed.