Brugian filariasis: 10-year follow-up study on the effectiveness of selective chemotherapy with diethylcarbamazine on Che Ju island, Republic of Korea.

The results of a 10-year follow-up of Brugia malayi microfilarial (mf) carrier rates in seven villages on Che Ju island and adjacent islets are reported; four villages initially received large-scale selective treatment with diethylcarbamazine (DEC) and three served as untreated controls. Some 90% of the total population took part in the pre-treatment blood survey and 82% of the detected mf carriers completed a course of treatment with 72 mg DEC per kg body weight over a period of 24 days.In the DEC-treated villages 92% of the mf carriers were negative one year after the treatment: the mf rate fell from 18.2% to 3.3%, the median mf density (MfD-50) changed from 28.4 to 5.2 mf/20 mm(3) blood, and the infectivity rate in Aedes togoi fell from 5.5% to nil. Ten years later these parameters had risen only slightly to 4.1%, 5.7 mf/20 mm(3) blood, and 0.3%, respectively. By contrast, in the untreated control villages none of these parameters changed significantly during the same period.Thus, selective DEC treatment of detected mf carriers is an excellent control measure for human filariasis as it is readily acceptable by the inhabitants and is cost-effective. Suitable intervals between treatments would be 8-10 years in areas where the mf prevalence rate is 10% or over, and 12-15 years where the prevalence is less than 10%.