Assessment of Malaria Vectors in Three ecological zones of Kigali City

Abstract

Background: Vectors, biologically defined as insects that transmit pathogens to humans, play a critical role in disease transmission. Among them, mosquitoes are considered an important class of vectors. Malaria remains a major public health concern, and understanding vector ecology is essential for effective control. This study 
aimed to assess malaria vectors in three ecological zones of Kigali city: Kabuye,  Niboye, and Vuganyana. Methods: A cross-sectional study was conducted in the three sites. Malaria vectors were collected using the Human Landing Catch (HLC) mosquito sampling method. Identification of Anopheles species was performed at the Kicukiro sentinel site entomology laboratory using entomological microscopy and morphological identification keys. ELISA tests were conducted at the National Entomological Laboratory of the Rwanda Biomedical Center to determine sporozoite infectivity. Results: The results of the study revealed clear variations across the three ecological zones. At the Kabuye site, An. gambiae s.l. was the dominant species, with a density of 7.1 b/p/n, accounting for 72% of the total collections, and showing a sporozoite rate of 0.55%. Other vectors identified included An. coustani (2.26%) and An. ziemanni (1.69%). At the Niboye site, An. gambiae s.l. had a density of 1.33 b/p/n, representing 13.53% of the total collections, but with zero sporozoite rate; additional  
species included An. coustani (3.17%) and An. ziemanni (2.74%). The Vuganyana site recorded the lowest density of An. gambiae s.l. at 0.16 b/p/n, representing 1.69% of the total collections, also with zero sporozoite rate, alongside An. coustani (1.69%) and An. ziemanni (2.11%). Overall, An. gambiae s.l. emerged as the major malaria 
vector, particularly dominant in Kabuye, an ecosystem characterized by rice cultivation. The Entomological Inoculation Rate (EIR) was calculated at 14, underscoring the high transmission potential in this area. Conclusion: This study demonstrates that An. gambiae s.l. is the primary malaria vector in Kigali’s ecological zones, with significant infectivity observed in Kabuye. Other species, including An. coustani and An. ziemanni, were present but showed no sporozoite infectivity. Given the high transmission risk in marshy and rice cultivation areas, effective malaria control strategies should include mosquito nets, indoor residual spraying, 
environmental management, repellents (coils, vaporizers), and larvicides. Future research should further investigate the ecology and infectivity potential of secondary vectors to strengthen malaria prevention efforts in Rwanda.