Background: Long-lasting insecticidal nets (LLINs) are essential for malaria control, but their effectiveness is threatened by increasing resistance of Anopheles to pyrethroids. In 2021, Côte d'Ivoire distributed both standard and new-generation LLINs during its mass distribution campaign. This study assessed the physical integrity and residual efficacy of these nets 3 y after their distribution.
Methods: A cross-sectional survey was conducted in 10 health districts chosen for ecological diversity. A total of 570 LLINs were withdrawn from randomly selected households and evaluated through WHO cone bioassays using both the susceptible Anopheles gambiae strain, Kisumu, and a local pyrethroid-resistant strain from Tiassalé. Multivariate analysis was performed to explore factors influencing mosquito mortality.
Results: LLIN coverage remained high (2.49 nets per household; 86.6% usage). However, 58.25% of LLINs had at least one hole, especially among standard LLINs in the North. While full efficacy was retained against the Kisumu strain, mortality dropped to 50% against the resistant strain. New-generation LLINs were more effective in the North, whereas standard LLINs were more effective in the South.
Conclusion: These findings underscore the importance of adapting LLIN distribution strategies to local resistance profiles and maintaining regular monitoring to ensure sustained protection and guide vector control policies.
Keywords: Anopheles gambiae; Côte d’Ivoire; insecticide resistance; long-lasting insecticidal nets; physical durability; residual efficacy.
© The Author(s) 2025. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene.