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 m 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).