Écologie des habitats larvaires, utilisation des moustiquaires imprégnées et résistance aux pyréthrinoïdes des Anopheles gambiae s.l. dans deux agroécosystèmes périurbains de Kinshasa, République démocratique du Congo

Abstract

Background. Urban and peri-urban agroecosystems can create aquatic habitats conducive to malaria vectors, while resistance to pyrethroids can reduce the effectiveness of insecticide-based interventions. This study characterized the larval habitats and susceptibility status of Anopheles gambiae s.l. in two agricultural areas of Kinshasa, with a community component focusing on insecticide-treated bed nets (ITNs). Methods. A cross-sectional survey was conducted among 300 households in Herady. Forty larval breeding sites were characterized in Herady and Mbanza-Lemba (20 per site) between March and May 2026. Temperature, pH, conductivity, turbidity, and salinity were measured. Larvae were reared to the adult stage; females were subjected to WHO tube bioassays with permethrin, deltamethrin, and alpha-cypermethrin, with and without prior exposure to PBO. Comparisons used parametric or nonparametric tests depending on the data distribution. Results. Of the 300 households, 171 (57.0%) had received ITNs during the most recent campaign; of the 244 mosquito nets assessed, 122 (50.0%) were in poor condition and 151 (61.9%) were hung over the sleeping area. All breeding sites were associated with the river and wet/marshy soils. Herady had a higher temperature (26.35 ± 1.16 °C) and pH (8.31 ± 0.34) than Mbanza-Lemba (23.75 ± 1.02 °C and 7.61 ± 0.64; p < 0.001 for both). The persistence of larval habitats (Fisher's exact p = 0.047) and their coverage (p = 0.010) differed between sites. Bioassays indicated mortality below the WHO susceptibility threshold for all three pyrethroids at both sites; these values should nonetheless be interpreted with caution, as minor inconsistencies were noted between counts and percentages in the source table. Conclusion. The two agroecosystems studied harbor larval habitats with distinct characteristics, and the available data suggest phenotypic resistance to pyrethroids. Coverage and integrity of insecticide-treated bed nets in Herady are also suboptimal. Direct quantification of agricultural exposures and validation of the bioassays remain necessary before attributing the observed resistance to agricultural practices.