Genetic diversity of swine influenza viruses in Thai swine farms, 2011–2014

Abstract

The pig is known as a "mixing vessel" for influenza A viruses. The co-circulation of multiple influenza A subtypes in pig populations can lead to novel reassortant strains. For this study, swine influenza surveillance was conducted from September 2011 to February 2014 on 46 swine farms in Thailand. In total, 78 swine influenza viruses were isolated from 2,821 nasal swabs, and 12 were selected for characterization by whole genome sequencing. Our results showed that the co-circulation of swine influenza subtypes H1N1, H3N2, and H1N2 in Thai swine farms was observable throughout the 3 years of surveillance. Furthermore, we repeatedly found reassortant viruses between endemic swine influenza viruses and pandemic H1N1 2009. This observation suggests that there is significant and rapid evolution of swine influenza viruses in swine. Thus, continuous surveillance is critical for monitoring novel reassortant influenza A viruses in Thai swine populations.

Appearance of reassortant European avian-origin H1 influenza A viruses of swine in Vietnam

“…EA‐like H1N1 IAV‐S was detected in 2001 and became dominant after 2005 in China (Vijaykrishna et al., ). Reassortant IAVs‐S containing genes derived from EA‐like H1N1 IAVs‐S have been reported in Thailand since 2000 (Abe et al., ; Nonthabenjawan et al., ; Poonsuk, Sangthong, Petcharat, & Lekcharoensuk, ; Takemae et al., ), and a reassortant among EA‐like H1 IAVs‐S, North American triple reassortant (TR) IAVs‐S and A(H1N1)pdm09v was identified in South Korea in 2013 (Lee et al., ). Our previous IAVs‐S surveillance in Vietnam (from 2010 to 2015), the second‐largest pig‐producing country in Asia, detected the introduction of H1 or H3 TR IAV‐S, human seasonal H1 that had circulated before 2009 and H3N2 viruses, and A(H1N1)pdm09 viruses into the Vietnamese pig population (Takemae et al., ).…”

Persistence of pdm2009-H1N1 internal genes of swine influenza in pigs, Thailand

“…In this study, we conducted a longitudinal survey in a pig farm from January 2017 to November 2018. The previous study on S-IAVs in this pig farm in 2015 showed that this pig farm had been infected with S-IAVs and estimated prevalence of S-IAVs was 6.66% 5 . Comparing to previous study, the S-IAV prevalence in this study was 18.81% (from January 2017 to November 2018), which was higher than previous report in 2015.…”

“…Comparing to the previous study in Thailand during 2000-2014, three subtypes of S-IAVs were identified, but S-IAV-H1N2 could not be identified in this study. Notably, S-IAV-H1N2 has lower prevalence than S-IAV-H1N1 and S-IAV-H3N2 5,19 . Phylogenetic analysis of H1 gene showed that S-IAVs in this study as well as endemic Thai-S-IAVs belonged to www.nature.com/scientificreports/ www.nature.com/scientificreports/ the distinct sublineage 1A.1.2 of classical swine (CS) 5,9 .…”

“…Notably, S-IAV-H1N2 has lower prevalence than S-IAV-H1N1 and S-IAV-H3N2 5,19 . Phylogenetic analysis of H1 gene showed that S-IAVs in this study as well as endemic Thai-S-IAVs belonged to www.nature.com/scientificreports/ www.nature.com/scientificreports/ the distinct sublineage 1A.1.2 of classical swine (CS) 5,9 . Based on the MCC phylogenetic tree, the H1 gene of S-IAVs in this study was estimated to have separated from endemic S-IAVs-H1N1 since 2010 ( Fig.…”

A Systematic Review Analyzing the Prevalence and Circulation of Influenza Viruses in Swine Population Worldwide

“…Several studies reported H1N1, A(H1N1)pdm09, H1N2, and H3N2 viruses in swine exhibiting respiratory disease symptoms between 2000 to 2014. Intriguingly, one swine sample was found co-infected with four IAV subtypes including H1N1, H1N2, H3N1, and H3N2 viruses [146][147][148][149][150][151][152].…”