Is biological larviciding against malaria a starting point for integrated multi-disease control? Observations from a cluster randomized trial in rural Burkina Faso

Abstract

Objectives To evaluate the impact of anti-malaria biological larviciding with Bacillus thuringiensis israelensis on non-primary target mosquito species in a rural African setting. Methods A total of 127 villages were distributed in three study arms, each with different larviciding options in public spaces: i) no treatment, ii) full or iii) guided intervention. Geographically close villages were grouped in clusters to avoid contamination between treated and untreated villages. Adult mosquitoes were captured in light traps inside and outside houses during the rainy seasons of a baseline and an intervention year. After enumeration, a negative binomial regression was used to determine the reductions achieved in the different mosquito species through larviciding. Results Malaria larviciding interventions showed only limited or no impact against Culex mosquitoes; by contrast, reductions of up to 34% were achieved against Aedes when all detected breeding sites were treated. Culex mosquitoes were captured in high abundance in semi-urban settings while more Aedes were found in rural villages. Conclusions Future malaria larviciding programs should consider expanding onto the breeding habitats of other disease vectors, such as Aedes and Culex and evaluate their potential impact. Since the major cost components of such interventions are labor and transport, other disease vectors could be targeted at little additional cost.

Larviciding intervention targeting malaria vectors also affects Culex mosquito distribution in the city of Yaoundé, Cameroon

“…The larval control trial was associated with 36% reduction of adult Culex mosquito densities. Similar reductions have been reported previously in Burkina Faso and Tanzania ( Geissbühler et al, 2009 ; Dambach et al, 2021 ). The low reduction rate compared to anophelines ( Antonio-Nkondjio et al, 2021 ) could be associated to the complex ecology of Culex mosquitoes in urban settings.…”

Larviciding intervention targeting malaria vectors also affects Culex mosquito distribution in the city of Yaoundé, Cameroon.

“…The larval control trial was associated with 36% reduction of adult Culex mosquito densities. Similar reductions have been reported previously in Burkina Faso and Tanzania [27,28]. The low reduction rate compared to anophelines [20] could be associated to the complex ecology of Culex mosquitoes in urban settings.…”

The impact of Bacillus thuringiensis var israelensis (Bti) larvicide sprayed using drones for bio-control of malaria vectors in rice fields of Kigali Sub-Urban, Rwanda

“…The larviciding trial with VectorMax® G conducted in Yaoundé, Cameroon found out an impact both on malaria vectors and culex mosquitoes with reduction of 69% and 36.6% in aquatic habitats and adult density inside houses for culex species, respectively (Talipouo et al, 2023). The impact on other mosquito species such as Aedes spp and Culex mosquitoes was also found to be limited in some settings (Dambach et al, 2021). The timing of larviciding, exhaustive and accurate geo-locations and types of mosquito habitats were the primary hindrances to optimize the impact of LSM, and thus requiring the new technologies (Hardy et al, 2017(Hardy et al, & 2023.…”