Abstract: Haemophilus parasuis had complicated diversities of serovars and genotypes. In this study, the H.parasuis isolated from the same farm were investigated the serovars by indirect hemagglutination test, and the outer membrane protein P5 genes were cloned, sequenced and analyzed with the neighbor-joining dendrogram from some strains. The results showed that the 42 H.parasuis strains were isolated and identified from the 21 diseased or died pigs. The serotyping results showed that there were 17 of serovar 5 (17/42, 40.7%), 12 of serovar 14 (12/42,28.5%), 1 of serovar 4 (1/42,2.3%) and non-typable (12/42,28.5%). Interestingly, we found that two different serovars simultaneously isolated in the same pig. Based on the difference of ompP5 gene sequences, the five different sequence types (STs, A to E) were identified from 21 isolates, in which STA was the predominant type in isolates. Furthermore, we also found that the isolates of the same serovar had different ompP5 STs, and even the isolates from the same pig also had different serovars and ompP5 STs. The above results exhibited that the serovar and genotype of H.parasuis isolated from the same pig farm possessed the obvious diversity, and serovars and genotypes infected the same pig also existed the diversities. Hence, this study further revealed the infectious complication of H.parasuis in pig farm, and provided valuable information for the study of infection and epidemiology in H.parasuis.

Key words: Haemophilus parasuis; serovar; outer membrane protein P5; genotype; diveristy