Studies on echinococcosis. II. Echinococcosis in Japan.

Though the hydatid cysts of this parasite have been found sporadically among domestic animals and human beings, in Japan until recently there has for many years been no adequate explanation of their occurrence.The question of autochthonous human hydatid infections in this country has been brought into sharp focus since the pathologists and surgeons of the Hokkaido University have discovered that hyatid infections show up with relatively high frequency among the residents of Rebun Island.This is a small island about 30 miles off the northwest coast of the Hokkaido main island, with an area of 80 km 2 and 10,000 inhabitants.At the request of the Hokkaido Health Department the first survey of the island was planned in the summer of 1948.Since that time more than 10 surveys of the infection have been carried out among the native residents of that island for the purpose of finding a method of control if possible.Recently, on the other hand, all the members of the author's laboratory having cooperated in a survey of the hydatid cyst infections of this parasite have carried out the experimental studies.Here the author proposes to present an epidemiologic outline of this disease in Japan using both the results of his investigations and the reports of other investigators. Animal Cases of Hydatid Cyst InfectionsThe occurrence of hydatid cyst infection of domestic animals has been thought to be rare in Japan and the infection, of any, has been usually considered to be of foreign origin.Nevertheless, some cases of infection have been recorded that could not be attributed to a source outside of this country yet there seemed no adequate explanation for their occurrence.JANSON (1893) stated that there were some cases of echinococcosis of cattle which might have been brought into Kyushu from China.According to the late KOIZUMl, 0.5% of the cattle, 0.5% of the horses and less than 0.5% of the pigs in Tokyo have harboured the hydatid cysts.EGUCHI and IWATA (1949), in their