It is well known that pigs are a 'mixing vessel' for genetic reassortment of type A influenza viruses, which could yield a novel influenza virus with pandemic potential. Besides providing information to reduce the economic burden of influenza in the pig industry, surveillance of swine influenza virus (SIV) in pig populations could serve as an early detection system for a pandemic influenza virus.
In February 2011, we isolated an H1N1 and two H3N2 SIVs in Thailand. The former was an A(H1N)pdm09 (pdm) virus and the latter were reassortants with HA and NA genes derived from a contemporary Thai SIV, and the internal genes from a pdm virus. In Japan, pdm viruses were isolated in 2009 and 2010, and reassortants between contemporary Japanese SIVs and pdm viruses were also found in 2011 and 2012.
The SIV vaccine currently available in Japan may not be highly effective against the introduction of pdm viruses into Japanese pigs, and the antigenicity of the reassortant SIVs appears to be different from human seasonal influenza viruses, providing opportunity for them to infect humans. Evaluation of the economic burden of SIV in the pig industry is crucial for sustaining SIV monitoring in pigs.
(Viral Disease and Epidemiology Research Division)
References:
- Hiromoto Y. et al. (2012) Virus Res. 169:175-181
- Matsuu A. et al. (2012) Microbiol. Immunol. 56:792-803
