Epidemiological Survey Of H9N2 Avian Influenza Virus In Live Bird Markets In Some Regions In China

First isolated in 1994 in our country,H9N2 avian influenza virus(AIV)has spread across most of China.With its high infection rate and widespread distribution in poultry in our country,H9N2 AIV readily causes secondary infection,which causes the respiratory system disease and eggs drop.H9N2 AIV also infects humans and other mammals,and it has the potential to recombine with more highly pathogenic AIVs,increasing the risk for serious threats in poultry or public health security.Therefore,it is necessary to conduct an epidemiological survey of H9N2 AIV to monitor this virrus,which can reveal the prevalence and the epidemic law,so as to lay down the scientific control plans and correspondingly counteractions.In this research,we selected Shanghai,Jiangsu,Anhui and Guangdong 4 provinces(the Yangtze River Delta and Pearl River Delta)to sampling in April,August and October in 2014.We randomly collected 58 live bird markets(including 25 wholesale markets and 33 retail markets)and totally obtained 12635 swab samples.After sample collection and processing,AIVs were isolated and RT-PCR was used to detect HA and NA genes.Positive amplifications were sequenced and analyzed using Mega 5.0 and Excel software.The results show that H9N2 AIV with the total positive rate of 15.11%(1908/1 2635),and the positive rate of field points is 98.28%(57/58).Respectively,the virus separation rate of H9N2 AIV of chicken,duck,goose and pigeon was 22.98%(1730/7529)?3.62%(94/2594)?4.08%(67/1643)?2.09%(18/861);and the virus separation rate of H9N2 AIV of Shanghai,Jiangsu?Anhui and Guangdong was 24.11%(688/2853)?8.43%(284/3368)?15.27%(475/3110)?13.95%(461/3304).The results also show that with a positive correlation between the resident time of poultry in the live bird markets and the virus separation rate of H9N2 AIV,which increasing from 11.45%(within 8h)to 29.13%(more than 48 h).The differences of the virus separation rate between the wholesale markets(12.24%)and retail markets(34.40%)were significant.Results of phylogenetic analysis show that,all of the H9N2 AIVs detected belong to the h9.4.2.5 branch,which have been epidemic strains in our country since 2007.These data infer that at first,H9N2 AIV infection of poultry in live bird markets in the Yangtze River Delta and Pearl River Delta is highly prevalent(especially in chickens).Secondly,the increased detection of H9N2 AIV in poultry with longer residence times in the wholesale markets and transfer to the retail markets suggest that the live bird markets may play an intermediary role like an "amplifier" in the spread of the virus.Therefore,the live bird markets increase the risk for transmission and disease in humans.In summary,this research make a pathogenic epidemiological survey of H9N2 AIV in live poultry markets in the Yangtze River Delta and Pearl River Delta,which reveals the epidemic situation and dynamic distribution relationship in these regions.In order to the results are of great value to the poultry industry,and provide more scientific theoretical basis to the prevention and control of H9N2 AIV.