Durability study of Veeralin®, Olyset® Plus and MAGNet® insecticide-treated nets (ITNs) in Kurnool district, Andhra Pradesh, India.

BACKGROUND

India plans to eliminate malaria by 2030, targeting zero local cases by 2027. However, malaria remains prevalent in endemic regions. As a means of addressing this issue, insecticide-treated nets (ITNs) are crucial for prevention. In areas with pyrethroid-resistant vectors, studies indicate that ITNs containing pyrethroids and piperonyl butoxide (PBO) are more effective. However, their physical and chemical durability and bioefficacy in this setting require further evaluation. This study assessed the durability of two pyrethroid-PBO-treated nets and one pyrethroid-only-treated net to determine whether they met the World Health Organization (WHO)'s 3-year operational performance criteria for "long-lasting" classification.

METHODS

A total of 7570 ITNs-2664 Veeralin® (alpha-cypermethrin and PBO), 2246 Olyset® Plus (permethrin and PBO), and 2660 MAGNet® (alpha-cypermethrin)-were distributed among 4186 households, following village randomization in Kurnool district, Andhra Pradesh, India. Following the baseline survey, all distributed ITNs were followed up annually for 36 months to measure ITN survival and bioefficacy.

RESULTS

The median functional survival period of the ITNs was estimated at 8 years (interquartile range [IQR] 7.00-9.00 years) for Veeralin®, 5.67 (IQR 5.00-6.33) years for MAGNet®, and 2.51 (IQR 2.19-2.88) years for Olyset® Plus. Bioassays conducted 36 months post-distribution using susceptible mosquito strains revealed 24-h mortality rates of 93.5% (91.8-95.3) for Veeralin® ITNs, 45.0% (33.7-56.4) for MAGNet® ITNs, and 59.3% (50.7-68.70) for Olyset® Plus ITNs. The "optimally insecticidal" period (24-h mortality > 80%) was 30 months for Veeralin® ITNs (84.0% [77.3-90.9] mortality), 18 months for MAGNet® ITNs (94.6% [92.2-97.2] mortality), and 12 months for Olyset® Plus ITNs (98.2% [97.5-98.9] mortality). Bioassays using an alpha-cypermethrin-resistant strain at 36 months showed 68.5% (64.9-72.0) mortality for Veeralin® ITNs and 58.1% (52.0-64.2) mortality for Olyset® Plus ITNs. Community acceptability at 36 months was 88.5% for Veeralin® ITNs, 86.7% for MAGNet® ITNs, and 56.3% for Olyset® Plus ITNs.

CONCLUSIONS

In the Indian geographic setting, Veeralin® ITNs met the criterion to be considered long-lasting insecticidal nets, remaining in serviceable condition (96.1%) for more than 3 years. They remained optimally insecticidal against pyrethroid-resistant mosquitoes and susceptible mosquitoes for 3 years.