Pathogen Analysis, Prevention And Control Of The Capital Incidence Of Swine High Fever In Central Of Shandong Province

Swine High Fever Syndrome (SHFS), referred to as "Swine High Fever", symptoms offever relapsing, is caused by a variety of pathogens and difficult to cure. It has recently beenpopular with acute onset and high mortality, which has caused huge economic losses. Thereare various causes of the swine high fever, such as viruses, bacteria, mycoplasma, parasites,especially classical swine fever virus (CSFV), porcine reproductive and respiratory syndromevirus (PRRSV), pig II circovirus type2(PCV2) alone and mixed infections are the mostcommon. Therefore, it is significant for comprehensive diagnosis and immune prevention tocontrol the swine high fever by studying pathogenic characteristics and the interaction ofviruses, regularity of epidemic, characteristics of suffering pigs via investigation.To study the pathogenesis, regularity of epidemic, clinical changes of the Swine HighFever syndrome (SHFS), we diagnosed the Clinical symptoms and the pathological changesof109cases of56pig farms and collected363serum samples in central region of Shandongprovince from January2011to March2012. Three viruses were detected on tissue samples byhistopathological, immunohistochemical examination and PCR or RT-PCR, includingclassical swine fever virus (CSFV)， porcine reproductive and respiratory syndromevirus(PRRSV), porcine circovirus type2(PCV-2).Serological tests were used for detectingprevalence of CSFV，PRRS, and PCV-2antibody by ELISA. The results showed that all pigssuffering from high fever had been vaccinated by Classical Swine Fever vaccine, part of themby porcine reproductive and respiratory syndrome attenuated live vaccines, but none of themvaccinated by Circovirus. The detection rates of the lymphoid tissue with acute inflammation,interstitial pneumonia and viral encephalitis were highest, respectively92.3%,76.1%and66.1%. Sometimes there were mixed bacterial infections. The pathogenetic rates of CSFV,PRRSV and PCV2were respectively30.27%,66.97%, and41.28%. The co-infection rates ofCSFV and PRRSV, CSFV and PCV2, PRRSV and PCV2were respectively16.51%,6.42%and28.44%. And the triple infection rate was4.59%in addition other pathogenic infectionswere8.26%. Sequence analysis showed that the epidemic strains of CSFV were developingtowards being far away from the HCLV, and all PRRSV strains were highly pathogenic ones.Also PCV2was mainly the virulent Type-PCV2b. According to the results, CSFV、PRRSV and PCV2were the main pathogens which caused the Swine High Fever in central region ofShandong province, and co-infection was the main reason to the severe cases. SometimesMycoplasma and Haemophilus parasuis mixed infection in clinical cases. Therefore multipleinfections led to the Swine High Fever in central region of Shandong province.Considering the characteristics of primary, multiple and highly pathogenic of CSFV,PRRSV in the current swine high fever cases, which has decisive significance in makingeffective prevention of these two diseases to control the swine high fever. Until now there hasno effective medicines to treat these two kinds of the disease, so preventive vaccination is theonly method to control swine high fever. Although PRRS variant strains attenuated vaccinemakes a good immune effect, it will seriously affect the immune response of classical swinefever vaccine. To understand the Nsp2Δ1882-2241-deficient highly PRRS pathogenicvaccine’s influence on Swine fever spleen tube seedlings,30two-week-old piglets withoutCSFV, PRRSV antibodies test, were randomly divided into6groups: A group was negativecontrol group, injecting physiological saline in the3rd week; B group was swine fever spleenseedlings control group, only injecting swine fever spleen tube seedlings in the3rd week; Ingroup C inoculated with PRRSV vaccination TJM-F92attenuated vaccine in the3rd week; Ingroup D immunized with PRRSV JXA1-R attenuated vaccine in the3rd week. At the sametime group E immunized with PRRSV TJM-F92attenuated vaccineweak vaccine and swinefever spleen tube seedling. Group F inoculated with PRRSV JXA1-R attenuated vaccine weakvaccine and swine fever spleen tube seedlings at the same time. Drawed blood every weekfrom0to6weeks respectively, then detected antibody of PRRSV and CSFV in the serumwith ELISA method. And established the One-step SYBR Green I fluorescent quantitativeRT-PCR to quickly distinguish between PRRSV pandemic strain and TJM-F92vaccinestrains. The results showed that the antibody production with injecting PRRSV TJM-F92weak vaccine and swine fever spleen seedlings group has no obvious difference to the controlgroup separately, while the vaccine of CSFV and PRRSV JXA1attenuated vaccine injectingat the same time produces mutual inhibition,and fluorescent quantitative RT-PCR showedthat PRRSV TJM-F92group did not detect PRRSV virus disease caused by a pandemic strain,so measured antibody is caused by the vaccine. Above results indicated that the TJM-F92strain was not only maintained the good immunogenicity but also eliminated the inhibition ofswine fever vaccine with simultaneously or successively immunity, which has important practical significance for prevention of two diseases.