Bio-efficacy, physical integrity, community usage and washing practices of mosquito nets treated with ICON MAXX long-lasting insecticidal treatment in India

Background Vector control for malaria prevention relies most often on the use of insecticide-treated bed net (ITNs) and indoor residual spraying. Little is known about the longevity of long-lasting insecticidal nets (LLINs) in the Americas. The physical integrity and insecticide retention of LLINs over time were monitored after a bed net distribution campaign to assess community practices around LLIN care and use in Waspam, northeastern Nicaragua. Methods At least 30 nets were collected at 6, 12, 24, and 36 months post distribution. Physical integrity was measured by counting holes and classifying nets into categories (good, damaged, and too torn) depending on a proportionate hole index (pHI). Insecticide bioefficacy was assessed using cone bioassays, and insecticide content measured using a cyanopyrethroid field test (CFT). Results At 6 months, 87.3 % of LLINs were in good physical condition, while by 36 months this decreased to 20.6 %, with 38.2 % considered ‘too torn.’ The median pHI increased from 7 at the 6-month time point to 480.5 by 36 months. After 36 months of use, median mortality in cone bioassays was 2 % (range: 0–6 %) compared to 16 % (range: 2–70 %) at 6 months. There was a decrease in the level of deltamethrin detected on the surface of the LLINs with 100 % of tested LLINs tested at 12 months and 24 months crossing the threshold for being considered a failed net by CFT. Conclusions This first comprehensive analysis of LLIN durability in Central America revealed rapid loss of chemical bioefficacy and progressive physical damage over a 36-month period. Use of these findings to guide future LLIN interventions in malaria elimination settings in Nicaragua, and potentially elsewhere in the Americas, could help optimize the successful implementation of vector control strategies.

Section: Discussionsupporting

confidence: 58%

Evaluation of the durability and use of long‐lasting insecticidal nets in Nicaragua

Villalta

Bravo²,

Vizcaino

et al. 2021

“…India contributes two third (n = 1,087,285) of the total malaria cases in South East Asia during 2016 [2]. The malaria burden in the country has been sustained by the presence of efficient vectors that maintain high levels of transmission [3]. Vector control remains an essential component and a fundamental element of malaria control strategy in India [4].…”

Section: Introductionmentioning

confidence: 99%

“…Due to the hurdles of achieving high coverage and quality, IRS was replaced with ITNs in most of the areas during 1990′s and has been accepted as a touchstone for malaria vector control [7]. ITNs were well received since last three decades and have been proven to give protection against malaria in many countries including India [3, 6]. However, successful implementation of ITNs was hampered by several technical, operational, economic and social factors [5].…”

Section: Introductionmentioning

confidence: 99%

“…To overcome this problem, use of long-lasting insecticidal nets (LLINs) has been encouraged by the World Health Organization (WHO) and extended to hard core malarious areas since last one decade [5]. In most of the LLINs made in the factory, insecticide is either incorporated into the fibres or coated on the fibres [3]. LLINs usually retain insecticidal bio-efficacy for 3 years without re-treatment and withstand 20 washes [8].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evaluation of MAGNet, a long-lasting insecticidal mosquito net against Anopheles fluviatilis in experimental huts in India

Kasinathan

Sahu

Vijayakumar

et al. 2019

Self Cite

Background MAGNet LN is a wash resistant long-lasting insecticidal (polyethylene) net (LLIN) in which the alpha-cypermethrin insecticide is incorporated within the 150 denier high density polyethylene monofilaments of the nets. The bio-efficacy of MAGNet LN was reported to be high even after 25 washes. The LN met the WHO criteria of Phase I evaluation and obtained recommendation from the World Health Organization Pesticide Evaluation Scheme (WHOPES) for Phase II trial. For registration of the LN in India, the current study was conducted to evaluate its efficacy after 20 or 25 washes compared to negative control (untreated net) and positive control (Duranet LN) in experimental huts against a wild, free flying pyrethroid susceptible population of Anopheles fluviatilis in terms of deterrence, blood-feeding inhibition, mortality and induced exophily. Methods The evaluation was carried out in six experimental huts located at Kandhaguda village in Malkangiri district, Odisha state following the WHO guidelines. Results The study showed that 25 times washed MAGNet LN produced 100% mortality in cone bioassays before and after hut evaluation. MAGNet washed 25 times did not differ significantly from all other treated nets in terms of deterring hut entry, induced exophily, blood feeding inhibition and causing mortality of An. fluviatilis. Conclusions MAGNet LN showed extended wash resistance retaining its bio-efficacy up to 25 washes and met the WHOPES requirement of passing Phase II evaluation. Electronic supplementary material The online version of this article (10.1186/s12936-019-2692-3) contains supplementary material, which is available to authorized users.

“…Additional experiments included 1 or 2 g/sq m micro-encapsulated PM without the binding agent. The binding agent is usually provided as part of a lambda-cyhalothrin based product, called Icon Maxx ® (Syngenta AG), used to extend the durability of long-lasting treatment of bed nets [ 20 ]. This dosage of BA was 14 times higher than that recommended for co-treatment with lambda-cyhalothrin, and was calculated based on the example for micro-encapsulated PM described in the patent for this technology [ 21 ].…”

Section: Methodsmentioning

confidence: 99%

Wash-resistance of pirimiphos-methyl insecticide treatments of window screens and eave baffles for killing indoor-feeding malaria vector mosquitoes: an experimental hut trial, South East of Zambia

Chinula

Sikaala

Chanda‐Kapata

et al. 2018

BackgroundThe effectiveness of long-lasting insecticidal-treated nets (LLINs) and indoor residual spraying (IRS) for malaria control is threatened by resistance to commonly used pyrethroid insecticides. Rotations, mosaics, combinations, or mixtures of insecticides from different complementary classes are recommended by the World Health Organization (WHO) for mitigating against resistance, but many of the alternatives to pyrethroids are prohibitively expensive to apply in large national IRS campaigns. Recent evaluations of window screens and eave baffles (WSEBs) treated with pirimiphos-methyl (PM), to selectively target insecticides inside houses, demonstrated malaria vector mortality rates equivalent or superior to IRS. However, the durability of efficacy when co-applied with polyacrylate-binding agents (BA) remains to be established. This study evaluated whether WSEBs, co-treated with PM and BA have comparable wash resistance to LLINs and might therefore remain insecticidal for years rather than months.MethodsWHO-recommended wire ball assays of insecticidal efficacy were applied to polyester netting treated with or without BA plus 1 or 2 g/sq m PM. They were then tested for insecticidal efficacy using fully susceptible insectary-reared Anopheles gambiae mosquitoes, following 0, 5, 10, 15, then 20 washes as per WHO-recommended protocols for accelerated ageing of LLINs. This was followed by a small-scale field trial in experimental huts to measure malaria vector mortality achieved by polyester netting WSEBs treated with BA and 2 g/sq m PM after 0, 10 and then 20 standardized washes, alongside recently applied IRS using PM.ResultsCo-treatment with BA and either dosage of PM remained insecticidal over 20 washes in the laboratory. In experimental huts, WSEBs treated with PM plus BA consistently killed similar proportions of Anopheles arabiensis mosquitoes to PM-IRS (both consistently ≥ 94%), even after 20 washes.ConclusionCo-treating WSEBs with both PM and BA results in wash-resistant insecticidal activity comparable with LLINs. Insecticide treatments for WSEBs may potentially last for years rather than months, therefore, reducing insecticide consumption by an order of magnitude relative to IRS. However, durability of WSEBs will still have to be assessed in real houses under representative field conditions of exposure to wear and tear, sunlight and rain.Electronic supplementary materialThe online version of this article (10.1186/s12936-018-2309-2) contains supplementary material, which is available to authorized users.