Efficacy of Bacillus sphaericus in control of the filariasis vector Culex quinquefasciatus in an urban area of Olinda, Brazil

The efficacy of Bacillus sphaericus 2362 against Culex quinquefasciatus was tested in 1991-94 in a major Brazilian endemic zone for bancroftian filari asis. Continuous selection pressure against the mosquito population was sus tained for 18 months through treatment of 2500 potential breeding sites occ urring within a 5(.)7-km(2) urban area in the Metropolitan Region of Recife . The impact of this control intervention was evaluated by comparing entomo logical indices with those from an untreated area. Application of the larvi cide kept the Cx. quinquefasciatus population density significantly lower w hen compared to the untreated area, despite some operational difficulties. Adult densities remained lower for at least 5 months after spraying ceased. Pre-trial microfilaria rates from the untreated and operational area were 13(.)1% and 7(.)2%, respectively. A 60% reduction in human exposure to infe ctive bites was recorded as a consequence of this vector population control .