Establishment And Preliminary Application Of PCR Method Of Haemophilus Parasuis

Haemophilus parasuis is a member of the family Pasteurellaceae and an important respiratory-tract pathogen of swine, which is the etiological of Glasser's disease characterized by fibrinous polyserositis, arthritis and meningitis. Haemophilus parasuis is a non-motile, Gram-negative bacterium. Currently, H.parasuis infections have being one of the important diseases which producing significant mortality and morbidity in piglets in pig farms. It has caused an important, economic losses in pig industry in China.The purpose of the present study was to determine the prevalence of Haemophilus parasuis(HPs) infection in different regions. After the clinical epidemiological investigation and pathological observation, and one species-specific PCR assay amplifying the genes of H.parasuis encoding 16S small subunit ribosomal RNA. Because of the fastidious growth of the bacteria and the trouble traditional biochemical tests, a PCR assay was developed to detect Haemophilus parasuis. The results showed that the PCR assay could be used to detect H.parasuis, associated with bacteria isolate for lung sample quickly and accurately. During the period from November 2003 to April 2005, the lung samples of clinical piglets from one hundred fifty-nine pig farms were tested by isolation and PCR for the presence of Haemophilus parasuis. The results showed that Haemophilus parasuis was detected in the samples from 76 of 159 pig farms(48%), and the positivity rate was related to the season, pig age, and geographic district. It suggested that Haemophilus parasuis was widely spreading in different re- gions of China. The weaned piglets were used as a model to evaluate pathogenesis of three Haemophilus parasuis isolates to piglets. The pigs challenged by the isolate had mildly elevated rectal temperature, and were reluctant to move. The gross lesions consisted of a severe fibrinous e×udates, and lage amounts of turbid fluid within the leural, pericardial, and peritoneal cavities, local lung hemorrhages and congestion of brain. The macroscopic lesions were characterized by fibrinous polyserositis, meningitis, and bronchopneumonia, containing large number of neutrophils lymphocytes.It indicated the Haemophilus parasuis isolates are high pathogenic potential strains, and can cause severe systemic disease.