An epidemiological survey of cystic echinococcosis among Tibetan school pupils in West China.

Human cystic echinococcosis (CE) caused by infection with a larval stage of Echinococcus granulosus is a serious public health problem in West China. Because CE is a zoonosis, dogs and livestock are important hosts in transmission. Tibetans, especially teenagers, have a natural relationship with these definitive and intermediate hosts in West China and although some areas of Tibet are therefore CE-endemic, few, if any, detailed community studies have been reported. A total of 451 Tibetan school pupils living in rural Tianzhou County in Gansu Province in West China were investigated by mass ELISA and IHA with ultrasound scanning back-up, and positivity rates were found to be 9.5% and 1.6%, respectively, with 0.98% confirmation of hepatic CE in four asymptomatic cases. Seropositivity rates varied with age between 6.2% and 13.2%. IHA found that females had a significantly greater risk of infection than males, a ratio of about 3:1. Age-specific immunopositive rates increased from 6.2% in the 8-13-years age group to 13.2% in those aged over 18. The study found that keeping dogs and herding animals had no effect on rates of infection but that the number of sheep owned by a family correlated with infection rates. The rate of infection in people who hunted was significantly higher than in those who did not. Level of education was found to have no effect on rates of infection.