Genotyping of Haemophilus parasuis from diseased pigs in China and prevalence of two coexisting virus pathogens

From December 2003 to July 2006, a total of 131 (28.4%) Haemophilus parasuis strains were isolated from 462 cases examined in our diagnostic laboratory. These strains were isolated from clinically diseased pigs, and 50 of them along with 15 reference strains of all known serovars were subjected to PCR-FRLP (restriction fragment length polymorphism) analysis by tbpA gene. The analysis of the 1.9-kb tbpA amplicon using TaqI, AvaI and RsaI endonucleases produced 9 RFLP patterns for the15 reference strains and 13 patterns for the 50 field isolates. And the first three prevalent genotypes in China were DBN (38%), ABN (18%) and DBP (12%). Meanwhile, co-infection of H. parasuis, PRRSV and PCV2 was examined in the 462 pig herds. It is indicated that 11.5% cases (53), 27.9% cases (129) and 4.8% cases (22) were infected only by H. parasuis, PRRSV and PCV2, respectively; and 19.2% cases (89) and 3.0% cases (14) were co-infected with two or all of the three pathogens, respectively; the rest 33.6% cases (155) were not infected by any of the three pathogens. It is confirmed that H. parasuis existed widely in southeast China with numerous genotypes.