Intestinal parasitic infections in hill-tribe schoolchildren in Chiang Mai, northern Thailand.

We surveyed intestinal parasitic infections in hill-tribe schoolchildren residing permanently in Chiang Mai Province. The positive rate, of 403 stool specimens examined using the formalin-ether sedimentation technique, was 48.9%. No significant difference between male (50.8%) and female (47.1%) students was found for the infection. The most common protozoa was Entamoeba coli (40.9%), followed by Giardia lamblia (14.9%). The most common helminth was hookworm (13.4%), followed by Ascaris lumbricoides (8.0%), and Trichuris trichiura (6.9%). Opisthorchis viverrini, the most important liver fluke infection in northern Thailand, was found in only 1.5%. Children harbored 1-5 species of parasites, with the most being single infections (67.5%), followed by double infections (26.9%). This finding promoted an urgent need for the treatment of infected schoolchildren, and the prevention of re-infection must be underlined.