湖北省武汉市大型规模化猪场猪圆环病毒2型流行病学调查

Epidemiological Investigation on PCV2 in Large-scale Farms in Wuhan City of Hubei Province

为掌握猪圆环病毒2型(porcine circovirus type 2,PCV2)在湖北省武汉市大型规模化养猪场的流行率,并探索该病的传播风险因素,从而为科学防控该病毒提供依据,2020年4—6月采取二阶段随机抽样方法,采集猪口腔液样品进行PCV2核酸检测。第一阶段,对武汉市所有大型规模化猪场,采用估计流行率的样本量计算方式,确定抽样场数后随机抽取猪场;第二阶段,在猪场内采取发现疫病的样本量计算方式,以栏舍为单位,计算需要随机抽取的栏舍数量。同时以调查问卷方式,对场点感染PCV2有关的风险因素进行调查。结果显示:共采集22个大型规模化猪场的330份猪口腔液样本进行检测,其中8个场的55份样本检出PCV2核酸阳性,场群表观流行率为36.4%,真实流行率为38.0%(95%CI,17.5%~58.5%),阳性场点分布在5个区(全部共6个区);净道、污道不分开是场内PCV2感染的主要风险因素。结果表明,武汉市大型规模猪场的PCV2场群流行率较高,分布范围较广,各场需加强生物安全管理,以控制PCV2的流行与传播。

In order to make clear the prevalence rate of porcine circovirus type 2(PCV2)in large-scale swine farms in Wuhan City of Hubei Province,seek for the risk factors of virus spreading,and thereby provide a basis for scientific prevention and control of PCV2,pig oral fluid samples were collected by the two-stage random sampling method from April to June in 2020 to detect PCV2 nucleic acids.In the first stage,the farms were randomly selected when the number of farms to be sampled was determined by means of sample size calculation of estimated prevalence;and in the second stage,the number of pens to be randomly sampled was calculated by the sampling strategy of finding diseases.Meanwhile,the risk factors related to the infection with PCV2 were investigated by means of questionnaire.The results showed that,for 330 samples collected from 22 large-scale farms,positive PCV2 nucleic acids were detected in 55 samples from 8 farms,the apparent prevalence rate of farms/herds was 36.4%,and the true prevalence rate was 38.0% (95%CI,17.5%-58.5%),the positive sites were distributed in 5 districts(there were 6 districts in total);and theclean and dirty passages were mixed together,which was the major risk of infection. In conclusion,the occurrence andspreading of PCV2 should be controlled through strengthening biosafety management in all farms where the virus waswidely distributed with high prevalence.