Abundance and biting habits of anopheline mosquitoes, and malaria incidence in Rwandan lowlands: analysis of 9 years data from two entomological surveillance sentinel sites

Abstract

Abstract Background Studies have explored sociodemographic factors that drive malaria morbidity in Rwanda. Little is known about the contribution of entomology in the transmission of malaria in the endemic lowlands of Rwanda. This study aimed to assess the composition, and behavior of anopheles species, and the dynamics of malaria transmission in Eastern Province, Rwanda. Methods This cross-sectional study used data captured by the national entomological surveillance system from January 2012 to December 2020. Mosquitoes were collected twice monthly in three different villages at each sentinel site, using Human Landing Catches (HLC) method. This data together with monthly malaria incidence was used for the descriptive analyses. Results Anopheles gambiae species was the most abundant at Rukara (72.92%), and Mimuri (99.23%) sentinel sites. Rukara recorded 15 different anopheline species, while the Mimuri site recorded only 2 species. The vector abundance has decreased tremendously over the study period, but malaria incidence remains high in the Rukara sentinel site, where anopheline species are unevenly distributed, while the incidence has significantly reduced at the Mimuri site. An. Gambiae spp, the most abundant anopheline species were exophagic (mean endophagic index < 0.5), and their mean human biting rates were 18.5 ± 20.52 and 65.7 ± 94.83 bites/ person/ night at Rukara and Mimuri, respectively. Conclusion These results highlight that an. gambiae complex anophelines are the most important malaria vectors in Eastern Province, and they predominantly bite outdoors. These findings also help us understand why indoor malaria interventions alone will not control malaria. Therefore, interventions that target outdoor mosquito density and bites are recommended.