Brief survey of common intestinal parasites in the Tokyo Metropolitan Area

Since 1955, when sanitary conditions were poor, the incidence of intestinal parasitism has steadily decreased. Similarly, the number of requests for fecal examinations by physicians has also decreased. However, in our hospital, the incidence of parasites detected in fecal material has been increasing since 1994, regardless of the decreasing number of stool exams performed. Possible reasons for this situation can be summarized as follows: First, an effective drug for treating Trichuris trichiura and Enterobius vermicularis infections has reduced the incidence of these two helminths. Second, an apparent increase in the incidence of infections with the tapeworms Diphyllobothrium latum and Diplogonoporus grandis may just be a reflection of patients gathering at a few facilities for treatment. Third, the number of individuals infected with a single Ascaris is significantly increasing. Fourth, parasites related with travel abroad (Schistosoma haematobium and Opisthorchis viverrini) are appearing due to the increase in travel to and from foreign countries. Of the above, we think particular attention should be paid to the increase in A. lumbricoides infections.