Serological report of pandemic and seasonal human influenza virus infection in dogs in southern China

From January to July 2012, we looked for evidence of subclinical A (H1N1) pdm09 and seasonal human influenza viruses infections in healthy dogs in China. Sera from a total of 1920 dogs were collected from Guangdong, Guangxi, Fujian and Jiangxi provinces. We also examined archived sera from 66 dogs and cats that were collected during 2008 from these provinces. Using hemagglutination inhibition (HI) and microneutralization (MN) assays, we found that only the dogs sampled in 2012 had elevated antibodies (≥1:32) against A(H1N1)pdm09 virus and seasonal human influenza viruses: Of the 1920 dog sera, 20.5 % (n = 393) had elevated antibodies against influenza A(H1N1) pdm09 by the HI assay, 1.1 % (n = 22), and 4.7 % (n = 91) of the 1920 dogs sera had elevated antibodies against human seasonal H1N1 influenza virus and human seasonal H3N2 influenza virus by the HI assay. Compared with dogs that were raised on farms, dogs that were raised as pets were more likely to have elevated antibodies against A(H1N1)pdm09 and seasonal human influenza viruses. Seropositivity was highest among pet dogs, which likely had more diverse and frequent exposures to humans than farm dogs. These findings will help us better understand which influenza A viruses are present in dogs and will contribute to the prevention and control of influenza A virus. Moreover, further in-depth study is necessary for us to understand what roles dogs play in the ecology of influenza A.