Epidemiological Investigation And Control Of CSF In Intensive Pig Farms In Longyan City

Classical swine fever (CSF) is a highly contagious and often fatal disease of swine caused by classical swine fever virus (CSFV). In order to control and elimination of this disease, increase the income and reduce the loss in pig industry in Longyan city, we study the epidemic features of CSF by epidemiological investigation, pathological anatomy, RT-PCR analysis and investigation of immune status. The results as follows:1. Detection of CSFV antigen:The prevalence situation, clinicopathologic features and diagnosis were analyzed in the suspect CSF cases from 17 intensive pig farms of Longyan. Reverse transcription-polymerase chain reaction (RT-PCR) was further used to detect clinical'samples. The result showed that 12 farms were CSFV antigen positive and the positive rates were 70.59%, indicating that CSF still is one of major contagious diseases in pig industry in our city.2. Detection of CSFV antibody:From January to December in 2009, the serum samples from 93 intensive pig farms of 7 counties were tested for CSFV antibody by enzyme-linked immunosorbent assays.4471 sera were serially collected from five group pigs, including 2161 sera from sows,280 sera from boars,415 sera from 10～25 day-old piglets,713 sera from 30～60 day-old nursing pigs and 946 sera from 120～180 day-old growing pigs. The antibody titers over the protective threshold in sows, boars, piglets, nursing pigs and growing pigs were 58.64%(1364/2161) 62.47%(176/280),42.16%(180/415),32.89%(307/713) and 62.23%(699/946), respectively. The result indicated that the antibody titers over the protective threshold were obviously lower in pigs, especially in piglets and nursing pigs, although most of pig farms have used CSFV vaccine immunization.3. Control and elimination of the CSF:Control and elimination of the CSF was performed ir sows and boars by enzyme-linked immunosorbent assays in intensive farms. The results indicated that the virus carried rate was high in swine if CSF antibody levels was abnormally lower and higher (blocking rate was less than 50% or more than 95%), and pigs showed immunosuppression or immunological tolerance by vaccine immunization. After cultivation of healthy breeding pigs, periodic detecting and developing rational immunization programs, we have achieved remarkable results:Average alive litter size was increased slightly (P=0.0983); Survival rate was improved by 2%; Stillbirth rate was decreased significantly (P<0.01) in pigs.