Seroprevalence and risk factors associated with Haemophilus parasuis infection in Tibetan pigs in Tibet.

Haemophilus parasuis is the causative agent of Glässer's disease, an important emerging infectious disease, but little is known of H. parasuis infection in Tibetan pigs in Tibet. The objective of the present investigation was to examine H. parasuis seroprevalence in Tibetan pigs in Tibet, China. Serum samples from 423 Tibetan pigs in Nyingchi, Tibet, China from April to December in 2010 were examined independently for the presence of antibodies against H. parasuis. A total of 147 (34.75%, 95% confidence interval [CI] 30.21-39.29) Tibetan pigs were tested positive for H. parasuis antibodies by the indirect hemagglutination assay (IHA) using a kit commercially available. 80 of 231 in Nyingchi (34.63%, 95% CI 28.50-40.77) and 67 of 192 in Mainling (34.89%, 95% CI 28.15-41.64) were tested positive, but the difference was not statistically significant (P>0.05, χ(2)=0.003). The prevalence ranged from 19.72% (95% CI 10.46-28.97) to 75.00% (95% CI 32.57-100) varying in different age groups, with higher prevalence in breeding boars than in piglets, and the difference was statistically significant (P<0.05). The prevalence of H. parasuis infection in males (45.03%, 95% CI 37.57-52.49) was significantly higher than that in the female (30%, 95% CI 22.41-37.59) pigs (P<0.05, χ(2)=7.361). Gender of Tibetan pigs was the main risk factor associated with H. parasuis infection. The results of the present survey indicated a wide distribution of H. parasuis among Tibetan pigs in Tibet, China and further investigation should better assess circulation of H. parasuis in Tibetan pigs. To the best of our knowledge, the present study represents the first report of H. parasuis infection in Tibetan pigs in China.