抄録
In Ichihara-gun, Chiba Prefecture, a rural district, two villages where no anti-hookworm measure had hitherto been taken were selected for the study. The inhabitants of these two villages were first given mass anthelmintic treatment twice, but after that no more anti-hookworm measure was taken. In such natural conditions, theconditions of newand re-infection were observed for more than one year's time byway of stool examination.
1. The hookworm egg-positive rates: 82.4% for Itohisa, Miwa-machi, and 41.2% for Nakano, Shitsu-mura. Both species were present, but Necator americanus predominated in either of the two areas.
2. The cumulative rates of new-and re-infection for the whole year: It was higher in Itohisa (36.9%) than in Nakano (8.4%). But, in the two other villages where antihookworm measures had been executed over a long period of time, such rate was extremely low.
3. The seasonal fluctuations of the rates of new-and re-infection: In both of these subject villages it was higher in the warmer season including the wet season, i. e. mid-April to mid-July.
4. Analysis of the rates of new-and re-infection by modesof living: In Itohisa, school children showed a higher rate of new-infection, and the adults of the same area presented the higher rates of both new-infection andre-infection.In Nakano, no significant difference was seen between school children and adults, but one thing to be noted is that the cases of conversion to positive among school children were all of them new-infection cases.
5. New-and re-infection rates by sex: No particular difference was recognized in either of the two areas.
6. Classification of new-and re-infection cases by species: In bothof the villages, majority of the cases carried Necator americanus only.
