Live bird markets as evolutionary epicentres of H9N2 low pathogenicity avian influenza viruses in Korea

Abstract

Live bird markets (LBMs) in Korea have been recognized as a reservoir, amplifier, and source of avian influenza viruses (AIVs); however, little was known about the role of LBMs in the epidemiology of AIVs in Korea until recently. Through 10 years of surveillance (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016) we have isolated and sequenced H9N2 viruses in Korean LBMs. To understand how H9N2 evolves and spreads in Korea, a statistical Bayesian phylogenetic model was used. Phylogenetic analysis suggests that three separate introductions of progenitor gene pools, Korean domestic duck-origin and two wild aquatic bird-origin AIVs, contributed to the generation of the five genotypes of H9N2 viruses in Korea. Phylogenetic reconstruction of ecological states infer that the LBMs are where chickens become infected with the virus, with domestic ducks playing a major role in the transmission and evolution of the H9N2 viruses. Three increases in the genetic diversity of H9N2 viruses were observed and coincided with transitions in host species and the locations (domestic farm, LBM, slaughterhouse, and wild aquatic bird habitat) where the viruses were isolated, accompanying genetic reassortment. Following the introduction of a wild aquatic bird-origin AIVs in 2008, six genes of the Korean lineage H9N2 virus were replaced with genes originating from wild aquatic birds, and viruses with this new genotype became predominant in Korean LBMs.

Avian Influenza Viruses Detected in Birds in Sub-Saharan Africa: A Systematic Review

“…These observations are consistent with previous studies in Iraq [ 119 ]. Moreover, H9N2 AIV infection is known to be endemic among poultry in Eurasia [ 120 , 121 ], and its circulation has been reported in North Africa, Europe and Asia among others [ 42 , 120 , 121 , 122 , 123 , 124 ]. H9N2 viruses are also known to circulate between wild birds and poultry sold at LBMs.…”

Detection of newly introduced Y280‐lineage H9N2 avian influenza viruses in live bird markets in Korea

“…The first outbreak of the H9N2 LPAIVs in Korea occurred in 1996 and the viruses from the outbreak were genetically close to the A/duck/Hong Kong/Y439/97 virus (Lee & Song, 2013). Since then, these H9N2 LPAIVs (Y439/Korea‐lineage) became prevalent only in Korea and evolved through reassortment with wild bird origin LPAIVs in live bird markets (LBMs), generating novel H9N2 genotypes (Youk et al., 2020). In response to the H9N2 endemic, the Korean government authorized the use of an inactivated H9N2 vaccine since 2007, and enhanced biosecurity measures and routine surveillance were implemented in LBMs.…”

First report of field cases of Y280-like LPAI H9N2 strains in South Korean poultry farms: pathological findings and genetic characterization

“…In June 2020, the existence of Y280-like H9N2 strains (that were distinct from previous Y439-like H9N2 strains that have been circulating since 1996) was confirmed by the government due to active surveillance in live bird markets (LBM), which were known epicentres for H9N2 LPAI in South Korea (APQA, 2020;Youk et al, 2020). Based on the descriptive characteristics of these new H9N2 strains in the report, no clinical signs or mortalities were observed in experimentally infected birds, and higher quantities of the virus shed through the oropharyngeal route compared to the cloacal route (APQA, 2020).…”