Email updates

Keep up to date with the latest news and content from Virology Journal and BioMed Central.

Open Access Highly Accessed Research

Pathogenesis of swine influenza virus (Thai isolates) in weanling pigs: an experimental trial

Donruethai Sreta1, Roongtham Kedkovid1, Sophon Tuamsang2, Pravina Kitikoon1 and Roongroje Thanawongnuwech1*

Author Affiliations

1 Chulalongkorn University, Bangkok, Thailand

2 National Institute of Animal Health, Bangkok, Thailand

For all author emails, please log on.

Virology Journal 2009, 6:34  doi:10.1186/1743-422X-6-34

Published: 25 March 2009



The objective of this study is to investigate the pathogenesis of swine influenza virus (SIV) subtype H1N1 and H3N2 (Thai isolates) in 22-day-old SPF pigs.


The study found that all pigs in the infected groups developed typical signs of flu-like symptoms on 1–4 days post- infection (dpi). The H1N1-infected pigs had greater lung lesion scores than those of the H3N2-infected pigs. Histopathological lesions related to swine influenza-induced lesions consisting of epithelial cells damage, airway plugging and peribronchial and perivascular mononuclear cell infiltration were present in both infected groups. Immunofluorescence and immunohistochemistry using nucleoprotein specific monoclonal antibodies revealed positive staining cells in lung sections of both infected groups at 2 and 4 dpi. Virus shedding was detected at 2 dpi from both infected groups as demonstrated by RT-PCR and virus isolation.


The results demonstrated that both SIV subtypes were able to induce flu-like symptoms and lung lesions in weanling pigs. However the severity of the diseases with regards to lung lesions both gross and microscopic lesions was greater in the H1N1-infected pigs. Based on phylogenetic analysis, haemagglutinin gene of subtype H1N1 from Thailand clustered with the classical H1 SIV sequences and neuraminidase gene clustered with virus of avian origin, whereas, both genes of H3N2 subtype clustered with H3N2 human-like SIV from the 1970s.