Eradication of bancroftian filariasis by diethylcarbamazine-medicated common salt on Little Kinmen (Liehyu district), Kinmen (Quemoy) Islands, Republic of China.

Since bancroftian filariasis constituted a major public health problem on Little Kinmen (Liehyu District), Kinmen (Quemoy) Islands, a control programme was conducted on this island from 1970 to 1982. A pre-control survey recorded a microfilarial rate (mfr) of 9.6%, a night blood microfilarial density (mfd) of 14.4/20 microliters blood, and a clinical rate of 26.2%. Culex quinquefasciatus was found to be the only vector of the parasitosis on the island, with an infection rate (Ir) with all filarial larval stages of 9.1% and a larval density (Ld) of 6.2. Diethylcarbamazine (DEC)-medicated salt (0.33% w/w) was administered to the whole population on Little Kinmen. Each person was estimated to take 12.7 g salt with 42 mg DEC daily for six months (July-December 1974). All accepted the programme, and no adverse side-effect was noted. During the control, the mfr and mfd were reduced to 0.3% and 1.9/20 microliters blood. The Ir and Ld were reduced to 0.8% and 1.3. Eight post-control surveys (1975-1982) revealed only two of 459 pre-control carriers positive and the remaining population of 7125 inhabitants negative. The two carriers were cured with a course of 5 g DEC. All family members of these carriers and their neighbours' families were given DEC-medicated salt for four months to clear the only remaining source of filarial transmission. In addition to a reduction in the prevalence of filariasis in humans and in mosquitoes to zero, the clinical manifestations disappeared in 52.4% of the pre-control carriers and improved in 19.0%. There was no change in 19.8 and 8.7% had new manifestations.