Physical integrity and survivorship of long-lasting insecticidal nets distributed to households of the same socio-cultural community in Benin, West Africa

Abstract

Background: Long-lasting insecticidal nets (LLINs) are designed to survive and sustain their physical barrier for 3 years in household conditions. However, studies have shown that most of these nets are usually torn or no longer present in the households in less than 3 years. This study was initiated in Benin to compare the survivorship and physical integrity of seven types of LLINs in a same socio-geographic area. Methods: In August 2017, 1890 households were selected in 9 villages in the municipality of Zagnanado in central Benin. Each one of the selected households received one of the seven LLIN products: Aspirational ® , DawaPlus ® 2.0, OlysetNet ® , PermaNet ® 2.0, PermaNet ® 3.0, Royal Sentry ® and Yorkool ®. Overall, 270 LLINs of each type were freely distributed in Zagnanado, at a rate of 30 LLINs per type per village. These bed nets have been monitored and evaluated every 6 months to identify the most resilient and preferred LLINs in the community. Net survivorship was assessed using the rate of net loss and physical condition. Results: The survivorship of all types of LLIN was estimated at 92% (95% CI 90.33-92.96) after 6 months and 70% (95% CI 67.25-71.81) after a year of use. At 12 months, all bed nets monitored were below the NetCalc model threshold of 92.8% for an LLIN with a lifespan of 3 years. Only 1.73% of all types of LLIN had a visible loss of integrity after 6 months with a median proportionate hole index (PHI) estimated at zero. The percentage significantly increased after 12 months with 10.41% of damaged nets (all types of LLINs). The median PHI for each brand of net was 23, 196, 141, 23, 23, 121 and 72, respectively for Aspirational ® , DawaPlus ® 2.0, OlysetNet ® , PermaNet ® 2.0, PermaNet ® 3.0, Royal Sentry ® and Yorkool ®. A significant difference was noted between the PHI at 6 and 12 months (p < 0.0001). After 12 months, the DawaPlus ® 2.0, OlysetNet ® and Royal Sentry ® suffered significantly more damage compared to the others (p < 0.001). Conclusion: The results of this study showed that after a year of use, the survivorship of the 7 LLIN products in households was lower than expected. However, all the LLIN products successfully met WHO standards for physical integrity after 12 months of use. The monitoring continues. The next steps will help to identify the most sustainable LLINs.

Variation of physical durability between LLIN products and net use environments: summary of findings from four African countries

“…While estimated median survival in serviceable condition was the same for PermaNet ® 2.0 and Netprotect ® with 2.6 years, there was strong statistical evidence that median survival for Olyset™ Net was lower with 2.0 years (p < 0.001). A study in Benin randomly distributed seven LLIN brands in one sub-district, four polyester-based, one polyester LLIN with enforced border and polyethylene roof (PermaNet 3.0) and two polyethylene-based LLIN and follow-up data up to 12 months did not suggest any differences by brand [ 23 ]. Finally, a recent secondary analysis and modelling of data from 3-year durability monitoring from seven countries involving between one and seven LLIN brands per country and using vectorial capacity as the primary outcome found more variability in decline of protection over time by country than by LLIN brand [ 24 ].…”

Digitalized mass distribution campaign of insecticide-treated nets (ITNs) in the particular context of Covid-19 pandemic in Benin: challenges and lessons learned

“…The NMCP of Benin has adopted a policy of mass distribution since 2011, on a triennial basis, considering the lifespan of ITNs, as previously evaluated in the country [ 8 ], and as recommended by the WHO [ 9 – 12 ]. The 4th mass distribution campaign took place in 2020 and has been digitized.…”

Digitalized mass distribution campaign of insecticide-treated nets (ITNs) in the particular context of Covid-19 pandemic in Benin: challenges and lessons learned

“…The NMCP of Benin has adopted a policy of mass distribution since 2011, on a triennial basis, considering the lifespan of ITNs, as previously evaluated in the country [8], and as recommended by the WHO [9][10][11][12]. The 4 th mass distribution campaign took place in 2020 and has been digitized.…”