2012年宁夏H5N1亚型高致病性禽流感疫情回顾性调查

Investigation of Highly Pathogenic Avian Influenza(H5N1)Outbreaks in Poultry in Ningxia,China,2012

[目的 ]2012年4月,宁夏当地报告蛋鸡发生疑似H5N1亚型高致病性禽流感(HPAI)疫情。为解本次疫情的流行病学特征、分析导致疫情发生的风险因素,在疫情发生后我们与当地兽医有关部门联合开展了回顾性暴发调查。[方法 ]以发生疫情的固原市头营镇所有的87个蛋鸡养殖场作为研究对象,采用问卷调查和抽样检测相结合的方式。对发病场采集病鸡的病料样品采用反转录-聚合酶链式反应(RT-PCR)或病毒分离来检测H5N1亚型禽流感病毒。采用多元回顾分析对疫情发生的风险因素进行研究,通过半方差图分析来证实发病场的聚集性分布。[结果 ]调查表明:H5N1疫情在头营镇分布广泛,其中有45户养殖场H5N1病毒RT-PCR呈阳性,其中4个养殖场病毒分离呈阳性。多变量模型分析表明:对废弃物不进行无害化处理(调整后的比值比OR为2.7,95%置信区间=1.20-8.30)和在疫情发生前一个月内有外来人员来访(调整后的比值比=5.5,95%置信区间=1.97-15.64)等两个因素可能与本次高致病性禽流感疫情有关。[结论 ]因此,频繁的人员流动和没有对废弃物进行无害化处理可增加感染发生的风险。为预防H5N1亚型HPAI感染的发生,应加强生物安全管理措施,包括限制外来人员来访和强化废弃物无害化处理等。

In April 2012,there were reports of suspected highly pathogenic avian inlfuenza（HPAI） H5N1 among poultry layers in Ningxia. A retrospective investigation was conducted to describe epidemiological characteristics of the outbreak and identify risk factors for HPAI H5N1 infection. Questionnaires were delivered to all the 87 layer farms in Touying Town,Guyuan County,Ningxia Province,within four weeks following the last reported outbreak. Samples of sick chickens were collected from 45 suspected farms to determine presence of H5N1 virus by reverse transcription polymerase chain reaction（RT-PCR） and confirmed by virus isolation. Multiple logistic regression analysis was used to identify the risk factors for infection and semivariogram analysis was used to demonstrate clustering of infected farms. Among 45 farms with positive PCR results,virus was isolated from four farms. Farms with improper waste disposal （adjusted OR = 2.7,95% CI = 1.20-8.30） and having visitors in farm within the past month（adjusted OR = 5.5, 95% CI = 1.97-15.64） were significantly associated with HPAI infection. Frequent human movement into farms and improper waste management increased the risk of infection. Biosecurity practices,including limiting number of visitors and proper waste disposal,should be enhanced to prevent further H5N1 infection.