CHINA - Pigs in the south of the country have been infected with multiple avian influenza viruses, according to new research at South China Agricultural University. No samples from pigs were found to be positive for the H7N9 subtype of the flu virus, however.
In 2013, a novel H7N9 avian influenza virus (AIV) was isolated from ill humans in Shanghai and Anhui Province in China, according to Guihong Zhang of South China Agricultural University and co-authors there and at the University of Florida in the US. Since then, they report in BMC Veterinary Research, the virus has spread quickly throughout China.
Previous isolation of H7N2 virus from swine suggests that additional H7 subtype AIVs may be transmitted through pigs. However, prior to the recent zoonosis of H7N9, there were very few studies on the seroprevalence of the H7 subtypes in this species. Thus, there was a need to perform serological surveys for novel H7N9 as well as other H7 subtype AIVs in swine. This surveillance may help us understand risk factors for outbreaks of influenza A (H7N9) virus, the researchers said.
Only 2.0 per cent (26/1310) of the pig sera had antibodies with an HI titre ≥1:20, and none had an MN titre ≥1:80 against the H7 antigen. Thus, no samples were found to be positive against H7N9.
However, 13.6 per cent (178/1310) of the pig sera had antibodies with HI titre ≥1:20 and 8.5 per cent (112/1310) by MN titre ≥1:80 against H9 antigen. Thirty-seven per cent (484/1310) of the pig sera had antibodies with HI titre ≥1:20 and 18.2 per cent (238/1310) had MN titre ≥1:80 against pandemic 2009.
Pigs in southern China have been shown to be infected with multiple avian influenza viruses, concluded Zhang and co-authors.
They added that, as the prevalence of novel influenza A viruses (e.g. H7N9 avian influenza virus) may be increasing among poultry in China, similar sero-epidemiological studies should also be conducted in pigs.
Zhou P., M. Hong, M.M. Merrill, H. He, L. Sun and G. Zhang. 2014. Serological report of influenza a (H7N9) infections among pigs in Southern China. BMC Veterinary Research. 10:203. doi:10.1186/s12917-014-0203-x
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