Serological Survey Of Haemophilus Parasuis In Sichuan And ERIC-PCR Fingerprinting Analysis Of The Field Isolates

Haemophilus parasuis invade multiple parts of the body when pigs appear weak, decreased immunity or other certain conditions to cause systemic disease, Hps is characterized by fibrinous serositis, arthritis and meningitis. The clinical diagnosis characteristics of Haemophilus parasuis is body temperature rising, breathing difficulties, joint swelling and movement disorders, a few pigs show neurological symptoms. In recent years, Hps has became one of the main bacterial diseases which producing significant morbidity and mortality in swine industry worldwide and the incidence of the disease is increasing year by year. This study focused on the serological epidemiological investigation of Hps in Sichuan area and the analysis of fingerprint ERIC-PCR of Hps wild strains, in order to provide the basic data for the study of epidemic dynamics and distribution of Haemophilus parasuis disease.1.Serological Investigation of Haemophilus parasuis in Sichuan areas658 swine serum samples from 16 regions in Sichuan were collected and detected by indirect ELISA method which was constructed in our lab before, which was used to investigate the prevalence Hps. The results indicated that 330 of 658 sera samples were HPS positive antibody, the total positive rate was 50.2%(330/658); For the different growth stages of pigs, the results shown that the positive rate were 36.4%(82/225),74.8%(225/302) and 17.6%(23/131) for suckling pigs, piglets and breeding pigs respectively.From the different collecting time,the results shown that the positive rate was 82.6%(190/231) in autumn; the positive rate was 43.2%(82/190) in winter;the positive rate was 24.2% (30/124) in spring;the positive rate was 24.8%(28/113) in summer.Results of serological investigation showed that:Haemophilus parasuis infection in pigs was prevalent in most areas of Sichuan, including Leshan, Deyang, Mianyang, Ya’an, Shuangliu, Ziyang, Dazhou and Meishan, and sera samples collected from these places were detected and the HPS antibody positive rates were 64.1%,46.6%,64.6%,57.6%,64.4%,78%,100%,65% respectively; Besides Hps antibody positive rate of nursery pigs was significantly higher than other growth stages of swine.2.Isolation and Identification of Haemophilus parasuis and ERIC-PCR fingerprinting analysis of the field isolatesA lot of lung, fibrin exudation, synovial fluid and hydrothorax samples which were suspected to be infected by Hps were collected, and 3 Hps strains were isolated. Microscopic appearance, satellite observation after Gram staining test, biochemical properties test and PCR test were used to identify this 3 strains, the final results showed that the 3 strains were all Haemophilus parasuis. Besides, the results of PCR test indicated that these strains were Haemophilus parasuis as well. We designed a primer based on the observe sequence ERIC and analyzed the fingerprinting of these 3 Hps strains by ERIC-PCR test. The results shown that ERIC-PCR fingerprint of field isolates were basically the same, indicating that these 3 trains could be the same genotype. This study successfully isolated 3 Haemophilus parasuis stains and attempted to apply the ERIC-PCR method for fingerprint analysis of Haemophilus parasuis.