J. Dossou-Yovo¹ , J. Chabi¹ , G. Carnevale² , P. Carnevale³

1 Pierre Richet Institute; BP 1500; Bouaké; Côte d'Ivoire
2 Jalan Raya Sakah, Batuan, Sukawati; 80582, Bali, Indonesia
3 Le Majoral building Portiragnes France (Director of Pierre Richet Institute at the time of the study)
Author    Correspondence author
Journal of Mosquito Research, 2026, Vol. 16, No. 4   
Received: 24 Aug., 2026    Accepted: 18 Sep., 2026    Published: 29 Sep., 2026

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The efficacy of lambdacyhalothrin-treated nets (« λITN”) on malaria transmission and disease was assessed, for the first time at villages level, in Anopheles gambiae pyrethroid resistance areas of N Côte d’Ivoire The base line data were obtained during a survey on rice cultivation, malaria transmission and morbidity, considering villages in three agroecosystems of Northern Côte d’Ivoire: (i) uncultivated lowlands “R0”, (ii) lowlands with one annual rice cultivation, in the rainy season, “R1” and (iii) developed lowlands with two annual rice cultivation cycles, “R2”. It appeared that the density of “main vectors”, mainly An. gambiae and An. funestus in R0; mainly An. gambiae in R1 and R2, increased with rice cultivation but the average yearly entomological inoculation rate (around 150 infective bites/human being) were almost similar.

The study on lambdacyhalothrin-treated mosquito nets (λITN) entomological and epidemiological efficacy was then carried out in this zone of An. gambiae high level of kdr resistance to deal with the burning issue of efficacy of treated nets when vectors are pyrethroid resistant.

From the list of villages surveyed during the study “rice cultivation and malaria” four paired villages (four villages of R2; two villages in R1 and two villages in R0) were selected and matched according to demographic, sociological, and ecological criteria. Among each pair, a village was randomly allocated to receive lambdacyhalothrin insecticide treated mosquito nets while the four other villages remained in their original state for one year, and considered as “control”, they received λITNs the following year.

The entomological impact of the treated nets was evaluated simultaneously with epidemiological studies in the same villages. Epidemiological information was already published showing that lambdacyhalothrin-treated nets induced a 56% reduction of malaria disease in children below 60-month-old. Up to now entomological data were not yet published as the first author passed after a long disease. We decided to publish the data in attrition to Dr Dossou-Yovo.

Entomological surveys were based on night capture on human being inside their houses. The main vectors were always An. gambiae in the three agroecosystems plus An. funestus in R0.

After implementation of λITN the “entomological inoculation rate” (EIR) due to An. gambiae decreased in the four villages receiving λITN, by an average of 90%; while in the villages without λITN the EIR naturally decreased by 47%; meaning a 48% gained efficacy with λITN implementation.

Adding data of the two main vectors showed that installation of λITN reduced the entomological inoculation rate two times more than what naturally occurred without such nets (relative reduction of 52.8%). This entomological level efficacy was remarkably similar the 56% reduction of the malaria incidence rate, a level comparable to the one observed almost everywhere with implementation of classical Long-lasting insecticide-treated nets in insecticide susceptible vectors areas.

Malaria vector control at village scale level; Kdr pyrethroid resistant Anopheles gambiae; Entomological evaluation; lambdacyhalothrin-treated nets