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. 2022 Jul 2;21(1):210.
doi: 10.1186/s12936-022-04230-6.

Evaluation of the residual efficacy and physical durability of five long-lasting insecticidal nets (LLINs) in Senegal

El Hadji Diouf  1 , Mbaye Diouf  2 , Constentin Dieme  2 , Isabel Swamidoss  3 , El Hadji Malick Ngom  4 , Massila Wagué Senghor  2 , Modou Mbaye  5 , Abdoulaye Konaté  2 , Youssouph Coulibaly  2 , Dome Tine  5 , Ibrahima Dia  4 , Ellen Marie Dotson  3 , Ousmane Faye  2 , Lassana Konaté  2
Affiliations

Evaluation of the residual efficacy and physical durability of five long-lasting insecticidal nets (LLINs) in Senegal

El Hadji Diouf et al. Malar J. .

Abstract

Background: The preventive and curative strategies of malaria are based on promoting the use of long-lasting insecticidal nets (LLINs) and treating confirmed cases with artemisinin-based combination therapy. These strategies have led to a sharp decline in the burden of malaria, which remains a significant public health problem in sub-Saharan countries. The objective of this study was to determine and compare the residual efficacy of LLINs recommended by the World Health Organization.

Methods: The study was conducted in six villages in two sites in Senegal located in the Sahelo-Sudanian area of the Thiès region, 70 km from Dakar and in Mbagame, a semi-urban zone in the Senegal River Valley. A census was conducted of all sleeping places in each household to be covered by LLINs. Five brands of LLIN were distributed, and every six months, retention rates, net use, maintenance, physical integrity, insecticide chemical content, and biological efficacy were examined for each type of LLIN.

Results: A total of 3012 LLINs were distributed in 1249 households in both sites, with an average coverage rate of 94% (95% CI 92.68-95.3). After 36 months, the average retention rate was 12.5% and this rate was respectively 20.5%, 15.1%, 10%, 7%, and 3% for Olyset Net®, Dawa Plus® 2.0, PermaNet® 2.0, NetProtect® and Life Net®, respectively. The proportion of LLINs with holes and the average number of holes per mosquito net increased significantly during each follow-up, with a large predominance of size 1 (small) holes for all types of LLINs distributed. During the three-year follow-up, bioassay mortality rates of a susceptible strain of insectary reared Anopheles coluzzii decreased in the following net types: in Dawa Plus® 2.0 (100% to 51.7%), PermaNet® 2.0 (96.6% to 83%), and Olyset Net® (96.6% to 33.3%). Mortality rates remained at 100% in Life Net® over the same time period. After 36 months, the average insecticide content per brand of LLIN decreased by 40.9% for Dawa Plus® 2.0, 31% for PermaNet® 2.0, 39.6% for NetProtect® and 51.9% for Olyset Net® and 40.1% for Life Net.

Conclusions: Although some net types retained sufficient insecticidal activity, based on all durability parameters measured, none of the net types survived longer than 2 years.

Keywords: Durability; LLINs; Residual biological efficacy; Retention; Senegal.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Localities where LLINs were distributed and durability monitored
Fig. 2
Fig. 2
Retained proportions not removed (red), retention after sampling (blue) and cumulative number of nets removed by type and semester after 3 years
Fig. 3
Fig. 3
Categories of holes by type and semester after 3 years. Size 1, size 2, size 3
Fig. 4
Fig. 4
Insecticide concentration in mg/m2 according to the type LLINs and semester
Fig. 5
Fig. 5
Correlation of chemical and bioassay results by type of LLIN and semester
Fig. 5
Fig. 5
Correlation of chemical and bioassay results by type of LLIN and semester
See this image and copyright information in PMC

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