Genetic characteristics and pathogenesis of H5 low pathogenic avian influenza viruses from wild birds and domestic ducks in South Korea

Yu-Na Lee,Yoon-Gi Baek,You-Chan Bae,Sun-Ha Cheon,Dong-Hun Lee,Yu-Ri Park,Youn-Jeong Lee,Soo-Jeong Kye,Myoung-Heon Lee,Gyeong-Beom Heo,Eun-Kyoung Lee,Young-Jae Si

doi:10.1038/s41598-020-68720-w

Abstract

H5 and H7 subtypes of low pathogenic avian influenza viruses (LPAIVs) can mutate to highly pathogenic forms and are therefore subject to stringent controls. We characterized H5 LPAIVs isolated from wild-bird habitats and duck farms in South Korea from 2010 to 2017. Through nationwide active surveillance for AIVs, 59 H5 LPAIVs were isolated from wild-bird habitats (a mean annual rate of 5.3% of AIV isolations). In 2015, one LPAI H5N3 strain was isolated on a duck farm. Phylogenetic analysis revealed that the hemagglutinin (HA) gene of H5 isolates belonged to the Eurasian lineage, classified into three subgroups (HA-II, HA-III, and HA-IV). The H5 LPAIVs of the HA-III and HA-IV subgroups appeared in 2015 and 2017 in unusually high proportions (13.1% and 14.4%, respectively). In gene-constellation analysis, H5 LPAIVs isolated from 2015 to 2017 constituted ≥ 35 distinct genotypes, representing high levels of genetic diversity. Representative strains of three HA subgroups replicated restrictively in specific-pathogen-free chickens. Among the 11 isolates that were tested, 10 infected and replicated in mice without prior adaptation. The frequency of recent H5 LPAIV isolates with high genetic diversity indicates the importance of continued surveillance in both wild birds and poultry to monitor genetic and pathobiological changes.

Highlights

H5 and H7 subtypes of low pathogenic avian influenza viruses (LPAIVs) can mutate to highly pathogenic forms and are subject to stringent controls
Our results have shown that the annual prevalence of Avian influenza viruses (AIVs) in samples from wild-bird habitats in South Korea was 0.2–1.5% from 2010 to 2017, which is consistent with values of 0.4–1.2% for major wild-bird habitats in South Korea from 2003 to 2 00829
The ability of the H5 and H7 subtypes of LPAIVs to mutate to HPAI viruses (HPAIVs) in poultry is the main reason for their stringent control

Summary

Introduction

H5 and H7 subtypes of low pathogenic avian influenza viruses (LPAIVs) can mutate to highly pathogenic forms and are subject to stringent controls. The HA genes of all H5 viruses identified in Korea since 2002 belonged to the Eurasian lineage and formed four distinct genetic subgroups (HA-I–IV) (Fig. 1B).

Results

Conclusion