Survival of eight LLIN brands 6, 12, 24 and 36 months after a mass distribution campaign in rural and urban settings in Senegal

Abstract

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 inaccording to arbitrary thresholds households under different field conditions. This study investigated survival of different LLIN brands in Senegal. Methods Ten thousand six hundred eight LLINs were distributed in five 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 models were used to estimate independent survival by net type (Interceptor®, Life Net®, MAGNet™, Netprotect®, Olyset® Net, PermaNet® 2.0 R, PermaNet® 2.0 C, Yorkool® LN) and by area (rural/urban). In addition to survival, median survival time and attrition of each LLIN brand was determined. Attrition was defined as nets that were missing because they were reported given away, destroyed and thrown away, 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 3 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 weak physical integrity and its median survival due to wear and tear was below 3 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. In this study in Senegal, conical PermaNet® 2.0 were retained in households while rectangular PermaNet® 2.0 had lower retention, suggesting that net shape may play a role in retention and should be further investigated. Distribution of preferred LLIN shape, accompanied by good communication on care and repair, could lead to increased effective lifespan, and allow for longer intervals between universal coverage campaigns.

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

“…This relationship was measured by the median index and revealed that more than half of Olyset Net ® type LLINs were in poor condition compared to Dawa Plus ® 2.0; all thirty Olyset Net ® sampled at 36 months had lost their physical barrier. This result corroborates those found recently in Senegal [ 39 ].…”

“…The low retention rate of the LLINs deployed in our study could be explained by the mass distribution campaign implemented in the area during the fifth semester or by the gifting of nets to relatives or friends observed during the first six months. A study has shown that, in Senegal, loss due to moving away is the most important during the first month post-distribution [ 39 ]. However other attrition factors related the loss and deterioration of LLINs are observed in the field during surveys.…”

Population knowledge, attitudes and practices towards malaria prevention in the locality of Makenene, Centre-Cameroon

“…In contrary, results by Talipouo et al [ 5 ] in Yaoundé (Cameroon) reported more than half of the LLINs in use in good condition. Diouf et al [ 48 ] concluded that the rapid degradation of mosquito nets would largely depends on their improper use (washing, drying, threading), which also depends on the year of acquisition. Messages about LLIN washing procedures should be disseminated in the locality to help maintain their integrity, effectiveness and sustainability.…”

Malaria prevention knowledge, attitudes, and practices (KAP) among adolescents living in an area of persistent transmission in Senegal: Results from a cross-sectional study

“…The low proportion of bed net ownership reported in this study could be explained by the fact that the study was conducted several years after a mass LLIN campaign where the majority of the distributed nets are likely no longer being used or functional. Indeed, while LLIN are expected to last at least 3 years, studies on LLIN durability, revealed that under routine conditions LLIN can lose effectiveness because they are physically damaged, repurposed or discarded [54,55]. Routine distribution of LLINs is also carried out at community level and in health facilities [14].…”