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

Abdou Talipouo; Patricia Doumbe-Belisse; Carmène S Ngadjeu; Landre Djamouko-Djonkam; Elysée Nchoutpouen; Roland Bamou; Nadège Sonhafouo-Chiana; Audrey Paul Marie Mayi; Gisèle Aurélie Dadji Foko; Parfait Awono-Ambene; Sévilor Kekeunou; Charles S Wondji; Christophe Antonio-Nkondjio

doi:10.1016/j.crpvbd.2023.100136

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

Curr Res Parasitol Vector Borne Dis. 2023 Jul 28:4:100136. doi: 10.1016/j.crpvbd.2023.100136. eCollection 2023.

Authors

Abdou Talipouo^{1

2}, Patricia Doumbe-Belisse^{1

2}, Carmène S Ngadjeu^{1

2}, Landre Djamouko-Djonkam^{1

3}, Elysée Nchoutpouen⁴, Roland Bamou^{1

3}, Nadège Sonhafouo-Chiana^{1

5}, Audrey Paul Marie Mayi^{1

3}, Gisèle Aurélie Dadji Foko⁶, Parfait Awono-Ambene¹, Sévilor Kekeunou², Charles S Wondji^{4

7}, Christophe Antonio-Nkondjio^{1

7}

Affiliations

¹ Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.
² Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon.
³ Faculty of Sciences, University of Dschang, Box 337, Dschang, Cameroon.
⁴ Centre for Research in Infectious Disease (CRID), Yaoundé, P.O. Box 13591, Cameroon.
⁵ Faculty of Health Sciences, University of Buea, Buea, Cameroon.
⁶ Laboratory of Zoology, Higher Teacher Training College, University of Yaoundé I, P.O. Box 47, Yaoundé, Cameroon.
⁷ Vector Biology Liverpool School of Tropical Medicine Pembroke Place, Liverpool, L3 5QA, UK.

Abstract

Although Culex species are considered to be equally affected by control measures targeting malaria vectors, there is still not enough evidence of the impact of interventions such as larviciding on the distribution of these mosquito species. The present study assessed the impact of a larviciding trial targeting malaria vectors on Culex mosquito species in the city of Yaoundé, Cameroon. A cluster randomized trial comparing 13 treated clusters and 13 untreated clusters was implemented. Data were collected at baseline and during the larviciding intervention, from March 2017 to November 2020. The microbial larvicide VectoMax G was applied once every 2 weeks in the intervention areas. Adult mosquitoes were collected using CDC light traps in both intervention and non-intervention areas and compared between arms. Globally, larviciding intervention was associated with 69% reduction in aquatic habitats with Culex larvae and 36.65% reduction of adult Culex densities in houses. Adult Culex densities were reduced both indoors (35.26%) and outdoors (42.37%). No change in the composition of Culex species was recorded. The study suggests a high impact of larviciding on Culex mosquito species distribution. The impact of the intervention can be improved if typical Culex breeding habitats including pit latrines are targeted.

Keywords: Bacillus sphaericus; Bacillus thuringiensis; Culex; Larviciding; Yaoundé.