Evaluation of the durability of long‐lasting insecticidal nets in Guatemala

Abstract

Background Insecticide-treated bed nets (ITNs) are widely used for the prevention and control of malaria. In Guatemala, since 2006, ITNs have been distributed free of charge in the highest risk malaria-endemic areas and constitute one of the primary vector control measures in the country. Despite relying on ITNs for almost 15 years, there is a lack of data to inform the timely replacement of ITNs whose effectiveness becomes diminished by routine use. Methods The survivorship, physical integrity, insecticide content and bio-efficacy of ITNs were assessed through cross-sectional surveys conducted at 18, 24 and 32 months after a 2012 distribution of PermaNet® 2.0 in a malaria focus in Guatemala. A working definition of ‘LLIN providing adequate protection’ was developed based on the combination of the previous parameters and usage of the net. A total of 988 ITNs were analysed (290 at 18 months, 349 at 24 months and 349 at 32 months). Results The functional survivorship of bed nets decreased over time, from 92% at 18 months, to 81% at 24 months and 69% at 32 months. Independent of the time of the survey, less than 80% of the bed nets that were still present in the household were reported to have been used the night before. The proportion of bed nets categorized as “in good condition” per World Health Organization (WHO) guidelines of the total hole surface area, diminished from 77% to 18 months to 58% at 32 months. The portion of ITNs with deltamethrin concentration less than 10 mg/m2 increased over time. Among the bed nets for which bioassays were conducted, the percentage that met WHO criteria for efficacy dropped from 90% to 18 months to 52% at 32 months. The proportion of long-lasting insecticidal nets (LLINs) providing adequate protection was 38% at 24 months and 21% at 32 months. Conclusions At 32 months, only one in five of the LLINs distributed in the campaign provided adequate protection in terms of survivorship, physical integrity, bio-efficacy and usage. Efforts to encourage the community to retain, use, and properly care for the LLINs may improve their impact. Durability assessments should be included in future campaigns.

Efficacy of Interceptor G2, Royal Guard and PermaNet 3.0 against pyrethroid- resistant Anopheles gambiae s.l. from Za-Kpota, Southern Benin: an experimental hut trial

“…This study also showed that while inducing high mortality compared to P2, IG2 aged induced signi cantly low mortality compared to new IG2. This could be due to a decrease in the insecticide content over time of ITNs in operational use, as demonstrated in several studies (43,44). In contrast, Martin et al(45) have demonstrated that after 20 washes (supposed to mimic a 36 months eld net) IG2 washed did not induce a signi cantly different mortality from IG2 unwashed, con rming the wash resistance of this net.…”

Coating formulation change leads to inferior performance of long-lasting insecticidal nets in Papua New Guinea

“…gambiae, Anopheles stephensi, Anopheles albimanus, Anopheles culicifacies, Anopheles arabiensis, Aedes aegypti and Culex quinquefasciatus from across various continents (Oceania, Asia, Africa and the Americas), as well as in mosquito colonies reared in European laboratories. A non-exhaustive list of these studies with confirmed pre-2013 PermaNet ® 2.0 nets includes the following studies (24 h mortality rates obtained with WHO cone bioassays are provided in parentheses): Katusele et al (100%) [ 20 ]; Kilian et al (100%) [ 21 ]; Castellanos et al (100%) [ 22 ]; Graham et al (100%) [ 23 ]; Kweka et al (100%) [ 24 ]; Okia et al (100%) [ 25 ]; Sreehari et al (100%) [ 26 ]; Kayedi et al (100%) [ 27 ]; Jarramillo et al (100%) [ 28 ]; Dery et al (100%) [ 29 ], and Sood et al (100%) [ 30 ].…”

Quantitative analysis of insecticides in long-lasting insecticidal nets using liquid chromatography mass spectrometry (LC-MS) and X-ray fluorescence (XRF) spectroscopy

“…One of the most promising alternative methods is x-ray fluorescence (XRF) spectroscopy. Researchers in Ghana, Ethiopia and Guatemala have demonstrated the utility of XRF for fast quantification of deltamethrin in the field, specifically, for durability assessment of PermaNet® LLINs after (3 -38) months of use [8, 24, 25]. While XRF has been shown to be able to quantify deltamathrin, little is known if this concept has been applied to other insecticides even though this is theoretically possible using the same methodology.…”