Residual efficacy of standard and new-generation long-lasting insecticidal nets 3 years after mass distribution in Côte d'Ivoire.

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 A total of 570 LLINs were withdrawn from randomly selected households and evaluated through WHO cone bioassays using both the susceptible Anopheles gambiae strain, Kisumu, and a local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.