Background: Long lasting insecticidal nets (LLIN) are one of the core components of global malaria prevention and control. The lifespan of LLIN varies widely depending on the population or environment, and randomized studies are required to compare LLIN in households under different field condition. This study investigated survival of different LLIN brands in Senegal.
Methods: 12,608 LLINs were distributed in 5 regions each stratified by rural and urban setting. As part of the longitudinal follow-up, 2222 nets were randomly sampled and monitored from 6 to 36 months. Using random effects for households, Bayesian model were allowed to estimate independent survival by net type and by area (rural/urban). The complement of survival, attrition and median survival time of each LLIN brand, was determined as those nets that were missing because they were reported given away, destroyed and thrown, or repurposed.
Results: Three net types had a proportion of survival above 80% after 24 months: Interceptor®87.8% (95% CI 80-93.4); conical PermaNet® 2.0 86.9% (95% CI 79.3-92.4) and Life Net® 85.6% (95% CI 75-93). At 36 months, conical PermaNet® 2.0 maintained a good survival rate, 79.5% (95% CI 65.9-88.8). The attrition due to redistributed nets showed that the two conical net types (PermaNet® 2.0 and Interceptor®) were more often retained by households and their median retention time was well above three years (median survival time =3.5 years for PermaNet® 2.0 and median survival time =4 years for Interceptor®). Despite this good retention, Interceptor® had a weak physical integrity and its median survival due to wear and tear was below three years (median survival time = 2.4 years). The odds ratio of survival was 2.5 times higher in rural settings than in urban settings (OR 2.5; 95% CI 1.7-3.7).
Conclusions: Differences in survival among LLIN may be driven by brand, shape or environmental setting. It appears that in Senegal, conical nets may be retained longer. This study suggests that a distribution of preferred LLIN brand, accompanied by good communication on care and repair, could lead to increased effective lifespan, and allow for longer intervals between universal coverage campaigns.