Characterization of malaria vectors in Huye District, Southern Rwanda

Background: Effective control of malaria requires knowledge of vector species, their feeding and resting behaviour as well as breeding habitats. The objective of this study was to determine malaria vector species abundance and identify their larval habitats in Huye district, southern Rwanda. Methods: Adult mosquitoes were collected indoors using light trap and pyrethrum spray catch techniques, and outdoors using light traps. Female Anopheles mosquitoes were identified to species level by morphological characteristics. Enzyme-linked Immunosorbent Assay (ELISA) was used to screen for Plasmodium falciparum circumsporozoite protein and host blood meal sources. Anopheles larvae were sampled using dippers and raised into adult mosquitoes which were identified morphologically. Results: Anopheles gambiae sensu lato comprised of 70% of the 567 Anopheles collected. Other Anopheles species identified were An. funestus 4%, An. squamosus 16.5%, An. maculipalpis 6.5%, An. ziemanni 1.7%, An. pharoensis 1.2 % and An. coustani 0.1%. The majority, 63.5% of the collected mosquitoes were from indoors collections. The overall human blood index was 0.509. The P. falciparum circumsporozoite protein was found in 11 mosquitos including 8 Anopheles gambiae s.l. and 3 secondary vectors out of the 567 tested. The overall sporozoite rate was 1.9%. A total of 661 Anopheline larvae from 22 larval habitats were collected. They comprised of An. gambiae s.l. (89%) and An. ziemanni (11%). The absolute breeding index was 86.4%. The most common larval habitats were in full sunlight with still water like rice paddies and pools of stagnant water. Conclusion: These findings show that Anopheles gambiae s.l. is the dominant malaria vector in the area with other vectors playing a secondary role in malaria transmission. Malaria interventions need to be strengthened to reduce even further the malaria transmission in the area.