Prevalence, associated risk factors, and phylogenetic analysis of Echinococcus granulosus isolated from freerange Tibetan pigs in Tibet, China.

The current study was performed to investigate the prevalence, associated risk factors exploration and phylogenetic analysis of Echinococcus granulosus (E. granulosus) genotypes isolated from Tibetan pigs. A total 373 Tibetan pigs were examined during 2014 and 2015, and the variables potentially associated with E. granulosus infection were explored with a multivariable logistic regression model. E. granulosus cysts (n=37) were collected from Tibetan pigs (lungs or livers). Fragments amplification of mitochondrial (mt) DNA of cox1 (shorter and longer) and atp6 were employed. The genotype of E. granulosus were identified by sequence and phylogenetic analysis. Results showed the prevalence of E. granulosus in Tibetan pigs was 9.9%. The prevalence of E. granulosus in male and female Tibetan pigs was 6.8% and 13.3%, with a significant difference in the two genders (P<0.05). In different seasons, the infection rate of E. granulosus in Tibetan pigs were ranged from 5.8% to 12.3%. E. granulosus infection rates in different growing stages of Tibetan pigs were ranged from 4.4% to 15.9%, with a statistical difference in the three stages (P<0.01). The prevalence of E. granulosus in Tibetan pigs were 7.9% in 2014 and 13.0% in 2015. Genders and growing stages were demonstrated to be risk factors to influence the prevalence significantly through multivariable logistic regression model. All the three fragments were successfully amplified from each of the 37 cysts. E. granulosus genotypes of G4 and G6 were identified by comparing with reference sequences of E. genotypes available at NCBI database and phylogenetic analysis by using MEGA software.