Skin test study of Bancroftian filariasis in Kuroshima Island, Okinawa: a 13-year longitudinal study during a control campaign.

A longitudinal study was performed in an island, endemic for Bancroftian filariasis, by blood survey and skin test from the beginning of a filariasis control campaign in 1967 through 1980. The initial microfilarial rate of 13.2% was successfully reduced to almost 0 by 1970, by the selective administration of diethylcarbamazine to microfilaria positives. The age distribution of skin-test positivity changed year by year, especially in the younger age groups. A marked reduction was seen in the positive rate in the 0- to 9- and 10- to 19-year-old age groups. The change of skin reactivity for all islanders was evaluated, and revealed a gradual decrease in the wheal-size over the observation period.