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Randomized Controlled Trial
. 2021 Aug 24;11(1):17101.
doi: 10.1038/s41598-021-96362-z.

High efficacy of microbial larvicides for malaria vectors control in the city of Yaounde Cameroon following a cluster randomized trial

Christophe Antonio-Nkondjio  1   2 , P Doumbe-Belisse  3   4 , L Djamouko-Djonkam  3   5 , C S Ngadjeu  3   4 , A Talipouo  3   4 , E Kopya  3   4 , R Bamou  3   5 , M P Audrey Mayi  5 , N Sonhafouo-Chiana  3   6 , D L Nkahe  4 , R Tabue  7 , D Achu Fosah  7 , Jude D Bigoga  8   9 , P Awono-Ambene  3 , Charles S Wondji  10   11
Affiliations
Randomized Controlled Trial

High efficacy of microbial larvicides for malaria vectors control in the city of Yaounde Cameroon following a cluster randomized trial

Christophe Antonio-Nkondjio et al. Sci Rep. .

Abstract

The rapid expansion of insecticide resistance and outdoor malaria transmission are affecting the efficacy of current malaria control measures. In urban settings, where malaria transmission is focal and breeding habitats are few, fixed and findable, the addition of anti-larval control measures could be efficient for malaria vector control. But field evidences for this approach remains scarce. Here we provide findings of a randomized-control larviciding trial conducted in the city of Yaoundé that support the efficacy of this approach. A two arms random control trial design including 26 clusters of 2 to 4 km2 each (13 clusters in the intervention area and 13 in the non-intervention area) was used to assess larviciding efficacy. The microbial larvicide VectoMax combining Bacillus thuringiensis var israelensis (Bti) and Bacillus sphaericus in a single granule was applied every 2 weeks in all standing water collection points. The anopheline density collected using CDC light traps was used as the primary outcome, secondary outcomes included the entomological inoculation rate, breeding habitats with anopheline larvae, and larval density. Baseline entomological data collection was conducted for 17 months from March 2017 to July 2018 and the intervention lasted 26 months from September 2018 to November 2020. The intervention was associated with a reduction of 68% of adult anopheline biting density and of 79% of the entomological inoculation rate (OR 0.21; 95% CI 0.14-0.30, P < 0.0001). A reduction of 68.27% was recorded for indoor biting anophelines and 57.74% for outdoor biting anophelines. No impact on the composition of anopheline species was recorded. A reduction of over 35% of adult Culex biting densities was recorded. The study indicated high efficacy of larviciding for reducing malaria transmission intensity in the city of Yaoundé. Larviciding could be part of an integrated control approach for controlling malaria vectors and other mosquito species in the urban environment.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Distribution of aquatic habitats with anopheline larvae before and during the larviciding intervention ((Non-larviciding intervention area (Non LCI), Larvicidng Intervention area (LCI)).
Figure 2
Figure 2
Fluctuation of anopheline biting density before and during larviciding intervention (Non-larviciding intervention area (Non LCI), Larvicidng Intervention area (LCI)).
Figure 3
Figure 3
A map of the city of Yaoundé presenting intervention and non-intervention sites. The administrative division of Cameroon is available in open access on the OpenStreetMap platform (https://www.openstreetmap.org/search?query=cameroon#map=6/ 7.406/12.283). ArcGIS version 10.2.2 sofware (ESRI, Redland, CA, USA; https://www.esri.com/enus/arcgis/about-arcgis/overview) was used to generate the map showing study sites in Yaoundé.
Figure 4
Figure 4
Trial profile design (RCT: Random Control Trial).
Figure 5
Figure 5
Duration of activities planned during the larviciding trial in the city of Yaounde.
See this image and copyright information in PMC

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