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

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.

Evaluation of Durability as a Function of Fabric Strength and Residual Bio-Efficacy for the Olyset Plus and Interceptor G2 LLINs after 3 Years of Field Use in Tanzania

“…The current proliferation of several LLIN brands in the market, although aimed at providing affordable LLINs owing to an increased demand, need to be subjected to appropriate and stringent checks to sieve out lower quality LLINs [ 46 ]. Data on LLIN durability under field conditions, that are provided by qualified testing laboratories, should serve to determine LLINs’ functional life and actual impact; they should also be used by the manufacturers to improve the quality of nets produced [ 45 , 47 ].…”

Nanosilver For Anopheles Control In Endemic Malaria

“…The ITN control method relies on pyrethroids, besides that a study conducted by Diouf in Senegal reported that the lack of effectiveness of using mosquito nets in controlling malaria is related to the washing of mosquito nets and patterns of good net conditions such as restless children's sleeping behavior, the size of mosquito nets that too small for a bed and conducive to stretching. 31 Evaluation and development of mosquito vector control carried out in ve regions in sub-Saharan Africa, namely by using multiple ITNs with ITN dual-AI types relative to standards, pyrethroids are only ITNs that still provide protection from malaria, especially when access and use are high. 32 While the IRS method is non-pyretorid and is effectively used for scale endemic areas considering that the insecticide will last a long time and the costs required are very economical.…”