Bancroftian filariasis on Pemba Island, Zanzibar, Tanzania: an update on the status in urban and semi-urban communities.

Cross-sectional clinical, parasitological and entomological surveys for bancroftian filariasis were conducted in Konde, Chake Chake and Kengeja, three urban and semiurban communities on Pemba Island, and the results were compared with similar surveys done 15 years earlier. The overall prevalences of clinical manifestations among males aged 15 years or more (n = 614) was remarkably similar to those recorded 15 years earlier: elephantiasis 1.4% in 1975 and 1.1% in 1990; hydrocele, 22.4% and 21.8%, respectively. However, when the communities were compared individually, there was a reduction in the hydrocele prevalence in Konde from 22.4% to 11.5% and an increase in Kengeja from 27.0% to 35.5%. The overall microfilarial prevalence found during night blood surveys of all individuals aged 1 year or more (n = 2687) was 9.7%, compared to 14.2% recorded in 1975. The reduction was most pronounced in Konde. Of 1052 female mosquitoes caught with CDC light traps, 95% were Culex quinquefasciatus and 5% Anopheles gambiae s.l. Infective larvae of Wuchereria bancrofti were found only in the former. The filariasis situation in urban and semiurban communities on Pemba Island appears not to have changed considerably over the last 15 years.