Phylogenetic and pathotypic characterization of newcastle disease virus in Tibetan chickens, China

Chickens are considered to be potential reservoirs of Newcastle disease virus (NDV). In this study, six Newcastle disease virus strains were isolated and characterized in Tibetan chickens. The HN gene was sequenced, and phylogenetic relationship to reference strains was studied. The phylogenetic analysis demonstrated that these six isolated strains were closely related to NDV isolates of the reference strains GQ245823, KT002186, KU527561, KJ563939, AY225110, EU305607, KM056357, Y18898, GQ245832, AF077761 and lasota strain. Among them, EU305607, KJ563939 and KM056357 were isolated from India, while lasota strain came from attenuated vaccine widely used in China. Then, mean death time (MDT) and intracerebral pathogenicity index (ICPI) were used to estimate the pathogenicity of the isolates. Pathogenicity experiment showed HNH1 and HN17 to be virulent. Our results indicated that genetically diverse viruses circulate in Tibetan chickens, and based upon the phlogeographic analysis, we estimated the origin of ancestral viruses of the isolates and its sister strains located in India and China (lasota strain). It indicates the importance of continuous surveillance to enhance current understanding of the genetic evolution of the NDV strains.(AU)

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.

First report of Chlamydiaceae seroprevalence in Tibetan pigs in Tibet, China.

The seroprevalence of Chlamydiaceae infection in Tibetan pigs in Tibet, China, was examined by indirect hemagglutination assay (IHA), between April, 2010, and December, 2010. A total of 71 of 427 serum samples (16.63%, 95% confidence interval [CI] 15.31-17.95] were positive for Chlamydiaceae antibodies. Forty Chlamydiaceae seropositives from 232 samples were recorded in sera from Nyingchi (17.24%, 95% CI 15.40-19.08) and 31 positives were recorded in 195 serum samples from Mainling (15.90%, 95% CI 14.02-17.78). The investigation showed that the prevalence in female animals was 17.61% (95% CI 15.22-20.00), and in male animals it was 12.72% (95% CI 11.07-14.37). The prevalence ranged from 0% to 20.61% (95% CI 17.81-23.48) among different age groups, with a higher prevalence in growing pigs (p<0.01). The results indicated that Chlamydiaceae infection was widespread in Tibetan pigs in Tibet, China, which is of public health concern in this region of the world. To our knowledge, this is the first report of Chlamydiaceae seroprevalence in Tibetan pigs in Tibet, China.

First report of Toxoplasma gondii prevalence in Tibetan pigs in Tibet, China.

Toxoplasma gondii infection is widely prevalent in humans and animals, including pigs throughout the world. In this study, the seroprevalence of T. gondii infection in Tibetan pigs in China was investigated for the first time. A total of 427 serum samples were collected from Tibetan pigs in Nyingchi prefecture, Tibet, between April and December 2010, and were assayed for antibodies to T. gondii using the modified agglutination test (MAT). Ninety-seven (22.72%) pigs were found to be positive with MAT titers of 1:25 or higher. Slaughter pigs had the highest seroprevalence, compared with seroprevalence in fattening pigs, growing pigs, or piglets, although the difference was not statistically significant (p≥0.05). The results of the present survey indicate that T. gondii is highly prevalent in Tibetan pigs in Tibet, which poses a significant public health concern in this unique region of the world.