Risk related to the transmission of H5N1 subtype avian influenza virus in the environment of poultry markets in Changsha, China / 中华流行病学杂志

ABSTRACT

Objective To investigate the risk of H5Nl subtype avian influenza virus (AIV)transmission in the poultry market environment in Changsha city.H5N1 antibody levels among the groups related occupational exposure and AIV nucleic acid in the environment of poultry markets were detected.The characteristics of hamagglutinin (HA) genes of H5N1 AIV in the environment were analyzed.Methods One district and one county from Changsha city were selected randomly and two poultry markets at inner city or township levels were selected in the same district or county respectively.H5N1 antibody of the occupational exposure groups in the poultry market was tested and AIV nucleic acid in the poultry market environnent monitored.One hundred and two blood samples of the occupational exposure groups were tested for H5N1 antibody with single radioimmunoassay diffusion hemolysis (SRH) while 160 environment samples(from sewage,birds stools,feathers and smearing samples of poultry cages) in the poultry market were also detected for AIV nucleic acid with real-time PCR method.Four sewage samples of H5N1 subtype AIV were collected from poultry markets in Changsha,and the HA genes of H5N1 subtype AIV amplified by RT-PCR and then sequenced with TA cloning.Amino acid sequence alignment and phylogenetic tree analysis were conducted by Lasergene and Mega 5.0 software.Results The results through H5N1 antibody monitoring program showed that H5N1 antibody positive rates from workers were 25.5％ (26/102),50.0％ (9/18) and 25.4％ (17/67) respectively in the poultry markets of township and inner cities.H5N1 antibody positive rate in the township poultry markets was higher than in the inner cities poultry markets.Results from the surveillance on AIV nucleic acid showed that the overall H5 subtype positive rate in Changsha poultry markets was 31.3％ (50/160),and the positive rate of townships poultry markets was 37.3％ (31/83 ),which were both higher than those from the inner cities poultry markets (24.7％,19/77).H5 subtype AIV positive rate was different in the tested specimens,with ranking of positive rates were sewage (50.0％,24/48),feathers (44.5％,4/9 ),birds stools ( 29.8％,14/47) and smearing samples of poultry cages (14.3％,8/56),with statistically significant differences (P＜0.01).Four H5N1 HA genes TA cloning were successfully constructed and identified as Eurasian branch,similar to viruses isolated in mainland China and Hong Kong in the same group,according to genetic analysis.Sequence data of the four HA genes showed the same feature of high pathogenicity,compared to the H5N 1 AIV from mainland China of human origin.The receptor specificities were still with avian influenza origin (QSG)and the connecting peptide between HA1 and HA2 possessing the polybasic motif (RERRRKK or RERRGKK).Conclusion One of the reasons for H5N1 antibody positive rate of 25.5％ among poultry markets workers was that there were large numbers of H5N 1 subtype AIV detected in the environment of poultry markets and HA genes of H5N 1 subtype AIV in the poultry markets environment carried molecular characteristics of highly pathogenic which could increase the risk for H5N1 subtype AIV transmission in the environment of poultry markets.