Studies On Etiology And Pathology Of C Group Streptococcus Zooepidemicus In Hunan Regions

From June 2006 to December 2007,we have made an epidemiological survey on 14 affected areas in Hunan regions.In the histological observation we accidentally found many plesiomorphic bacteria in the sick pig's organs,then we have made a study of bacterial pathogens of sick pigs in the corresponding epidemic disease areas.A strong pathogenic bacteria of C herd streptococcus zooepidemicus is identified by bacterial isolation and identification,serological testing,PCR sequence analysis, small animal disease testing and drug sensitivity tests.The bacteria can grow dew-like,colorless,transparent,moist,elevated,round,medium-sizedβ-hemolytic colonies on blood agar plates.Bacterial DNA sequence analysis showed that the nucleotide sequence was 99%,only the 604 base pairs have changed from G to T.This strain have a high pathogenic for mice and rabbit,and have the most sensitive for rabbit.Drug sensitive test showed that this strain of bacteria was sensitive to Pioneer v,nitrofurantoin,Cephradine,Pioneer cefotaxime,Piperacillin,and showing low sensitivity to Rifampicin,penicillin G,erythromycin.Commonly drug used on farms like cotrimoxazole,tetracycline,amikacin,kanamycin do not sensitive to this strain.The pathology study of C herd Streptococcus zooepidemicus and the cell lysate disease in mice,the results showed that cell lysate is Lower pathogenic in mice than bacteria.The toxin.Cell lysate can make Lungs of mice with mild bleeding and local emphysema,Lymph node bleeding and spleen micro-swelling.Histopathological examinations showed focal pulmonary hemorrhage,alveolar interval widened, Splenic corpuscle is to be smaller,Spleen lymphocytes reducted,lymph node vascular congestion,and loose germinal center lymphocytes Etc.Experimental piglets by artificial infection,it showed that C herd streptococcus zooepidemicus can cause high fever,typical of sepsis,joint swelling,heart crown fatty myxoid degeneration,bleeding spleen infarction,gallbladder bile thick,lobular consolidation of lung.Histological observation showed that interstitial pneumonia, systemic lymph node hemorrhage and necrosis,spleen hemorrhage,diffuse necrosis of spleen parenchymal cells,renal hemorrhage and local tissue necrosis ets.Beside, bacteria aggregate can be found in renal glomerulus.By Comparative Analysis with Clinical disease material,we found the clinical symptoms and Pathological changes is similar with artificial infection and swine high fever disease (Infected with blue ear virus Nsp2 gene and C herd streptococcus zooepidemicus).We can determined that the C herd streptococcus zooepidemicus plays an important role in the occurrence and development of swine high fever disease.