Abstract
H9N2 avian influenza viruses (AIVs) are highly prevalent and of low pathogenicity in domestic poultry. These viruses show a high genetic compatibility with other subtypes of AIVs and have been involved in the genesis of H5N1, H7N9 and H10N8 viruses causing severe infection in humans. The first case of human infection with H9N2 viruses in Hunan province of China have been confirmed in November 2013 and identified that H9N2 viruses from live poultry markets (LPMs) near the patient’s house could be the source of infection. However, the prevalence, distribution and genetic characteristics of H9N2 viruses in LPMs all over the province are not clear. We collected and tested 3943 environmental samples from 380 LPMs covering all 122 counties/districts of Hunan province from February to April, 2014. A total of 618 (15.7%) samples were H9 subtype positive and 200 (52.6%) markets in 98 (80.3%) counties/districts were contaminated with H9 subtype AIVs. We sequenced the entire coding sequences of the genomes of eleven H9N2 isolates from environmental samples. Phylogenetic analysis showed that the gene sequences of the H9N2 AIVs exhibited high homology (94.3%-100%). All eleven viruses were in a same branch in the phylogenetic trees and belonged to a same genotype. No gene reassortment had been found. Molecular analysis demonstrated that all the viruses had typical molecular characteristics of contemporary avian H9N2 influenza viruses. Continued surveillance of AIVs in LPMs is warranted for identification of further viral evolution and novel reassortants with pandemic potential.
Highlights
H9N2 avian influenza viruses (AIVs) are highly prevalent in domestic poultry in Asia since the early 1990’s [1, 2]
During the period from February to April of 2014, a total of 3943 environmental samples were collected from 380 live poultry markets (LPMs) covering all 122 counties/districts of Hunan province
We discovered that 15.7% samples were positive for H9, while more than half of the LPMs and more than four-fifths counties/districts were contaminated with H9 subtype viruses
Summary
H9N2 avian influenza viruses (AIVs) are highly prevalent in domestic poultry in Asia since the early 1990’s [1, 2]. These viruses are lowly virulent for poultry, frequently cause mild disease and rarely result in poultry deaths. They have been associated with severe morbidity and mortality in poultry when they co-infected with other pathogens [3]. H9N2 AIVs in Asia can be divided into three main lineages represented by their prototype strains based on antigenic and phylogenetic analysis of hemagglutinin: A/Chicken/Beijing/1/94 (BJ94) or the A/Duck/Hong Kong/Y280/97 (Y280), A/Quail/Hong Kong/G1/97 (G1), and A/Duck/Hong Kong/Y439/97 (Y439) or A/ Chicken/Korea/96323/96 [7]. A novel genotype (G57) or genotype S represented by A/chicken/Zhejiang/HJ/2007(HJ07) emerged in 2007 and became predominant in farm chickens in China since 2010 [10, 11]
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