Epidemiological Investigation Of Porcine Reproductive And Respiratory Syndrome In Shuangyashan City,Heilongjiang Province

Pig blue ear disease,also known as "porcine reproductive and respiratory syndrome"(PRRS),is an acute,high fatal swine infectious disease caused by the porcine reproductive and respiratory syndrome virus(PRRSV).The virus not only has very strong pathogenicity,but also has an extremely fast spread rate.The pig population has a very high incidence.After the pig becomes infected,it shows a rapid increase in body temperature above 40°C,depression,dyspnea,sepsis and ataxia.Other pigs have purple ears and hair ends.The incidence rate can reach 100%,the mortality rate can reach more than 50%,and the sow abortion rate can reach more than 30%.Once pigs become infected with porcine reproductive and respiratory syndrome virus,the vast majority of them are chronically poisoned and difficult to eliminate,leading to significant economic losses.In this study,a questionnaire survey,ELISA method,and PCR method were used to test swine serum samples,disease samples,swab samples and fecal samples from large-scale swine farms and free-ranging households in Shuangyashan City,Heilongjiang Province.A preliminary understanding of the epidemic situation in Shuangyashan was conducted,and according to the clinical practice,the technical measures for the prevention and control of porcine reproductive and respiratory syndrome were summarized and provided reference for pig farmers in our city.From October 2016 to October 2017,this study collected data from 59 large-scale pig farms with more than 500 stocks and 341 households in 8 counties(districts)of Shuangyashan City,Heilongjiang Province.The collected species included nursery pigs,growing pigs,gilts and breeding pigs in four different growth stages.The survey of epidemiological conditions was conducted through a questionnaire survey to lay the foundation for further serological surveys and etiological investigations.The investigation included basic information of the pigs,clinical symptoms,treatment status,disinfection,immunization,history of the epidemic,conditions of the natural environment and the diseased pig house.A total of 400 questionnaires were issued and 372 were recovered.From the statistical results of the questionnaires retrieved,there are 20 clinically diagnosed PRRSVs,accounting for 5.38% of the questionnaires.It shows that pigs in some pig farms in Shuangyashan City have clinical symptoms of porcine reproductive and respiratory syndrome.During this period,clinical performance was collected from eight counties(districts)in Baoqing County,Youyi County,Jixian County,Raohe County,Shuangyatai District,Baoshan District,Lingdong District,and Jianshan District,Shuangyashan City,Heilongjiang Province.780 serum samples of pigs that were healthy and not PRRSV-vaccinated.Among them,496 serum samples were collected from 27 large-scale pig farms with a population of more than 500,and 284 serum samples were collected from 53 households with a total population of less than 500.The ELISA was used to detect PRRS antibodies.The results showed that 153 serum samples were positive,with a positive rate of 19.62%.Among them,the positive rate was 19.76% in large-scale pig farms,and 19.37% in scattered farmers.15 farms in 27 large-scale pig farms and 37 farms in the 53 specialized breeding households that serum samples were all negative for antibody testing.According to statistics,from April to July is the peak period of the disease,pigs of different ages can be infected and nursery pigs have the highest incidence.The PRRSV infection rate of the scaled farms is lower than that of the scattered farmers.From October 2016 to October 2017,lung,liver,spleen,and lymph node tissues of 160 dead pigs with suspected PRRSV infection were aseptically collected from some pig farms in Shuangyashan City,Heilongjiang Province.The results showed that 34 cases of PCR detection results were positive for PRRSV,and the positive rate was 21.25%.At the same time,random samples of pigs from 30 pig farms with normal appearance and no clinical symptoms,including nasal swabs and feces samples,were used for pathogen detection.The results confirmed that there were 24 PRRSV infections,with a positive rate of 15.38%;the number of positive pig farms was 9 and the positive rate was 30.00%.The above investigation shows that pig reproductive and respiratory syndrome is present in all pig farms in the city.It is a potential risk for the healthy development of the swine industry in our city.Once a widespread outbreak occurs,it will cause huge losses.Therefore,it is necessary to do a lot of prevention and control measures to deal with the infection and spread of the virus.According to the problems during the survey visit,the following comprehensive measures for prevention and control were summed up: Do a good job of immunization work on several major diseases of pig farms to ensure immunization effects;Strengthen of biosafety measures and feeding and management;Control of secondary bacterial infections after infection;For pig farms that are positive for serology or positive for etiological detection but do not have obvious clinical symptoms,the pigs in different growth stages should be well-preserved and pigs with the virus should be eliminated as far as possible to ensure the health of the pigs.