上海地区活禽批发市场H9亚型禽流感病毒调查

为弄清上海地区活禽批发市场中H9禽流感病毒（Avian influenza virus,AIV）的流行情况及鸡群的免疫情况,2009年对上海三大活禽批发市场进行了采样监测。采用HI试验检测H9 AIV抗体、荧光RT-PCR试验和鸡胚接种分离鉴定病毒。共采集110批次1 646份血样和喉头泄殖腔棉拭样品,平均抗体合格率为60.27%,分离到H9病毒134株,其中4-6月和9-11月为全年中病毒分离的2个高峰期（样品带毒率均超过了10.00%）,明显比其它月份要高（其他月份均低于5.00%）,样品带毒率平均为8.14%。不同市场、不同地区采集的样品其抗体合格率和样品的带毒率也存在一定的差异。在30批分离到病毒的样品中,13批次已免疫H9N2油乳剂灭活苗且抗体合格率均大于70.00%的样品中分离到45株病毒（45/195）,其中6批次抗体合格率达到100%的样品中也分离到了病毒（8/90）,但带毒率明显比未经疫苗免疫的样品（79/255）低。调查结果表明养殖户对肉鸡群H9N2油乳剂灭活苗免疫重视程度不够,鸡群中带毒现象较普遍。疫苗免疫后能产生较高的免疫抗体,且抗体能减轻临床症状,降低带毒率,但不能完全阻止病毒复制,存在高抗体下带毒现象。

SURVEY OF H9 SUBTYPE AVIAN INFLUENZA VIRUS IN LIVE POULTRY MARKETS OF SHANGHAI

To investigate the epidemic status of H9 Avian influenza virus（H9 AIV）and immunological background in Shanghai live poultry markets,a total of 1 646 blood,tracheal and cloacal samples of 110 batches were collected in 2009 from three large live poultry markets.The H9 AIV antibody titer was assayed by HI test.Virus isolation and identification was conducted by chicken embryo inoculation and real-time RT-PCR.The average antibody positive rate was 60.27%.A total of 134 H9 subtype influenza viruses were isolated.The average isolation rate was 8.14% throughout the year.Viruses were isolated from more than 10% of samples from April to June or from September to November while viruses were isolated from less than 5.0% in other months.There were difference in antibody positive rate and virus isolation among markets and districts.Out of the 30 batches with positive samples,45 viruses were isolated from 195 samples of 13 batches,from which animals were immunized with inactivated H9N2 vaccine and their antibody positive rate was more than 70%.In addition,8 viruses were isolated from 90 samples of 6 batches with 100% antibody positive rate but the virus isolation was less than unvaccinated batches（79/255）.These data indicated that inactivated H9N2 vaccine was not widely used and virus carriers were prevalent.The strong antibody immunity was induced after vaccination,which could reduce clinical signs and the infection rate but could not prevent virus replication,causing animals produced high level of antibodies but still were virus carriers.