Abstract

A study was required to evaluate the prevalence of clonorchiasis among school children in the 7 differnet schools located near the Gumho basin and to determine the effectiveness of the anticlonorchis campaign conducted in that area. Surveys for Clonorchis sinensis and the worm burden in the same areas were compared for the period 1960-1970. Both surveys concentrated on children in grades 1-3 ranging from 6-11 years old. They were examined using primarily intradermal tests with Clonorchis antigen and followed by stool examinations. Stool examinations consisting of the formalin-ether sedimentation(Ritchie, 1948 ) and the Stoll egg-count techniques were performed in those cases which revealed positive and doubtful intradermal reactions. The overall prevalence rate for clonorchiasis was reduced from 13.4 per cent to 4.1 per cent. There was also a significant reduction in the worm burden, suggesting that no clonorchiasis will be found among chileren in the near future. In connection with this survey, the prevalence rate for intestinal helminths in 1960 was compared with 1970. The rate for Ascaris lumbricoides had decreased, while the rates for Trichuris trichiura and Trichostrongylus species had increased. No fluctuation in the rate of hookworm was observed during the past 10 years. Clearly, the present survey denotes a requirement for a combined procedure of health education and mass survey with intradermal testing. It has been found that these methods not only greatly reduce the prevalence of clonorchiasis but also is followed by the marked reductions of the worm burdens of the children examined.