Efficacité des traitements larvicides pour le contrôle des anophèles vecteurs de paludisme dans la ville de Yaoundé

Abstract

Vector control is becoming less effective due to the expansion of insecticides resistance, changes in mosquito biting and resting behaviour, and the low use of insecticide-treated nets. This situation requires additional measures to improve malaria control. Larviciding may be a complementary intervention capable of improving the effectiveness of current measures, but to date very few larviciding control trials have been conducted in Africa. In this study, we assessed the effectiveness of larval control, using vectoMax G larvicide in controlling mosquito populations in the city of Yaounde.This study was carried out over a 13 months period (november 2018 to november 2019) in 14 clusters in the city of Yaoundé, seven of which belonged to the control group and seven to the treated group. In treated clusters, all water bodies with or without larvae were treated with vectoMax G (combining the released species of Bacillus thuringiensis israelensis and Bacillus sphaericus) once every two weeks. Quality control of treatments were conducted 24 to 48 hours after treatment. Checking of water bodies were conducted in control clusters as well, once a month. Larval collection was done using the dipping method. During larval surveys, the presence and density of larvae and their stages of development were recorded. Anopheles larvae were collected from at least five breeding sites per clusters. They were preserved in 100% alcohol for morphological and molecular identifications by the PCR technique.The results showed that the use of vectoMax G larvicide in water bodies significantly decreased the presence and density of anopheline larvae. Reduction rates of more than 90% were observed at Essos, Shell Obili, Mendong and Mvog-Besti. A high reduction in the number of mosquito breeding sites was recorded in the dry season compared to the rainy season. Anopheles gambiae s.s. and Anopheles coluzzii were the two members of the Anopheles gambiae s.l. complex found in our study sites. Larviciding had no impact on the distribution of these two species. With frequencies greater than 85%, An. coluzzii remained the predominant species in treated and control areas before and during treatment.This study showed the effectiveness of larval control using VectoMax G biolarvicide, which should now be included in the interventions to be advocated in the context of malaria prevention in Cameroon.