Effectiveness of larviciding as a supplementary malaria vector control intervention in the lake endemic zone: A case study of Busia county, Kenya, 2022-2023

Abstract

Background: Malaria is a leading cause of morbidity and mortality globally, mostly in tropical countries, accounting for more than one  million deaths annually. Community-based larval source management using larviciding was recently introduced as a complementary tool  within the context of existing Integrated Vector Management strategies. This study aimed at generating evidence on the effectiveness of  microbial larvicides in reduction of mosquito larval densities in the mapped aquatic habitats to improve malaria control.

Methods: The  biolarvicides BACTIVEC® Bacillus thuringiensis var. israelensis and GRISELESF® Bacillus sphaericus were used. Products applications were  made aquatic habitats findable and fixed in selected areas of seven sub-counties in Busia County during the period of January to  December 2022. Larval densities were determined using a standard WHO protocol at each study area prior to and after larviciding.

Results: Anophilines and Culicines larval species of mosquitoes were both present in all the surveyed accumulated open water bodies.  The larval type of breeding habitat predominance rates was in the order; Rice fields (24%), Dams (23%), Swamps (21%), Puddles (12%),  Lagoon (9%), Fishpond (4%), Streams and Seepage pool (3%) each respectively, and Rivers (1%). Prior and post larviciding, the average  reduction in relative larvae colonization rate in all habitats aggregated was 95% (P <0.001).

Conclusions: The study showed the potential  effect of larviciding using biolarvicides of bacillus group to control vectors of mosquito borne diseases and its integration with indoor  residual spraying and insecticide treated nets in malaria prevention.