Seroepidemiology of Toxoplasma gondii infection among Chinese aboriginal and Han people residing in mountainous areas of northern Thailand

A seroepidemiological survey of Toxoplasma gondii infection among Chinese refugees, including Akka and Yau aborigines and Han people living in mountainous areas at elevations of 1,100-1,400 in in Chiang-Rai Province of northern Thailand, was conducted during January 2003 using the latex agglutination test. The overall seroprevalence of T gondii infection was 9.1% for Akka aborigines, 37.9% for Yau aborigines, and 7.9% for Han people, respectively. No significant gender difference in seroprevalence was found among any of the groups (P>0.05). The results of a multiple logistic regression analysis for Yau aborigines and Han people showed that the older the age, the higher the odds ratios (OR) of being seropositive (OR 3.0, 95% confidence interval [CI]=0.5 to 16.9, P<0.001 and OR 1.5, 95% CI=0.3 to 8.0, P=0.06 for the elderly group vs. the child group for the Yau aborigines and Han people, respectively). In contrast, the OR was lower among older Akka aboriginal populations (OR=0.1, 95% CI 0.0 to 0.4, P<0.001). Ethnically, Yau aboriginal populations had a significantly higher seroprevalence than did the Akka aborigines and Han people (P<0.001).