Quality Control of Long-Lasting Insecticidal Nets: Are We Neglecting It?

Karl, Stephan; Katusele, Michelle; Freeman, Timothy W.; Moore, Sarah

doi:10.1016/j.pt.2021.03.004

Cited by 25 publications

(46 citation statements)

References 21 publications

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“…The bioe cacy endpoints of KD60 or M24 are sensitive to small changes in insecticide surface concentration, with the critical ranges for bioe cacy differing between, and sometimes within, products [30]. Indeed, it has been shown that total insecticide content does not always correlate with bioe cacy [31].…”

Section: Introductionmentioning

confidence: 99%

Cone Bioassays Provide Reproducible Bioefficacy Estimates with Different Anopheline Mosquitoes and Can Be Used for Quality Assurance of Pyrethroid Insecticide Treated Nets

Mbwambo

Bubun

Mbuba

et al. 2022

Preprint

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Background Quality assurance (QA) of insecticide-treated nets (ITNs) delivered to malaria-endemic countries is conducted by measuring physiochemical parameters, but not bioefficacy against malaria mosquitoes. The cone bioassay provides a simple evaluation of ITN bioefficacy and its conditions and parameters are prescribed by the World Health Organization (WHO). This study explored utility of cone bioassays for pre-delivery QA of pyrethroid ITNs in two test facilities using different mosquito species to test the assumption that cone bioassays are consistent and reproducible across locations, mosquito strains, and laboratories. Methods Double-blinded bioassays were conducted on unused pyrethroid ITNs of 4 brands (5 nets/brand, 5 subsamples/net) that had been delivered for mass distribution in Papua New Guinea (PNG) having passed physiochemical testing of chemical content. Cone bioassays were performed on adjacent net pieces following WHO guidelines at the PNG Institute of Medical Research (PNGIMR) using pyrethroid susceptible Anopheles farauti s.s. and at Ifakara Health Institute (IHI), Tanzania using pyrethroid susceptible Anopheles gambiae s.s. Additionally, WHO tunnel tests was conducted at IHI on ITNs that did not meet cone bioefficacy thresholds. Results from IHI and PNGIMR were compared using Spearman’s Rank, Bland Altman and Cohen’s kappa. A literature review on the utility of cone bioassays for unused pyrethroid ITNs testing was also conducted. Results In cone bioassays, 13/20 nets (65%) met WHO bioefficacy criteria at IHI and 8/20 (40%) at PNGIMR. All nets met WHO bioefficacy criteria on combined cone/tunnel tests. Results from IHI and PNGIMR correlated on 60-minute knockdown (rs=0.6,p=0.002,n=20) and 24-hour mortality (rs=0.9,p<0.0001,n=20) but there was systematic bias between the results measured by Bland Altman. Of the 5 nets with discrepant result between IHI and PNGIMR, three had confidence intervals overlapping the 80% mortality threshold, with averages within 1-3% of the threshold. The agreement between the results to predict ITN failure was good with kappa=0.79 (0.53-1.00) and 90% accuracy. Conclusions WHO cone is a reproducible means to measure pyrethroid ITN bioefficacy using a combination of knockdown and mortality. In the absence of an alternative tests, cone tests could be used to assess the availability of active ingredients at the surface of ITN (where mosquitoes encounter it) as part of pre-delivery QA.

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Section: Introductionmentioning

confidence: 99%

Cone Bioassays Provide Reproducible Bioefficacy Estimates with Different Anopheline Mosquitoes and Can Be Used for Quality Assurance of Pyrethroid Insecticide Treated Nets

Mbwambo

Bubun

Mbuba

et al. 2022

Preprint

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“…The number of LLIN products available to donors has increased considerably over the last 10 years 4 . Normally, new candidate LLIN products undergo WHO-supervised assessment in a prequalification (PQ) process.…”

Section: Introductionmentioning

confidence: 99%

“…Normally, new candidate LLIN products undergo WHO-supervised assessment in a prequalification (PQ) process. The PQ process involves extensive validation of candidate product bioefficacy, and chemical and physical properties under laboratory and operational conditions 4,5 . The most widely used and robust tests to measure LLIN bioefficacy in the WHO prequalification process and in post-marketing surveillance, are standardized WHO cone bioassays in which pyrethroid susceptible mosquito strains are exposed to LLIN samples for 3 minutes 5 .…”

Section: Introductionmentioning

confidence: 99%

“…Once products have been PQ listed, they are eligible for donor-funded procurement, which drives the vast majority of the LLIN market 3 . Post marketing, LLIN quality assurance monitoring includes predelivery inspections in which total chemical active ingredient (AI) content, wash retention of the AI, and physical strength of LLINs are tested 4 .…”

Section: Introductionmentioning

confidence: 99%

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Effect of short-term heating on bioefficacy of deltamethrin-coated long-lasting insecticidal nets

Bubun

Freeman²,

Laman

et al. 2021

Preprint

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We recently reported that long-lasting insecticidal nets (LLINs) distributed in Papua New Guinea (PNG) between 2013 and 2019, exhibited severely diminished efficacy to knock down and kill susceptible Anopheles mosquitoes. This coincided with a rise in malaria observed in PNG since 2015. Here we show that LLIN bioefficacy is increased by heating LLINs prior to WHO cone bioassays. Unused LLINs with low bioefficacy, delivered to PNG in 2019, were heated to 120 degrees Celsius for 5 minutes. Cone bioassays were performed before and at 1 h, 7 days and 30 days after heating. This led to a significant increase in 24 h mortality (17% to 61%) and 60 min knock down (31% to 72%). The effect was sustained over 30 days. Bioassays are crucial in quality assurance of LLIN products. Our findings indicate that bioassay results can easily be manipulated. This may have implications for quality assurance procedures used to assess LLINs.

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“…SMC requires the administration of the anti-malarial drugs sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) monthly for four months during the high transmission season to prevent malaria and is recommended by WHO across the Sahel Region 7 . Potential explanations for the stagnating progress in malaria control include low ITN usage or lack of ITN bioe cacy and durability [8][9][10][11] , a rise in the resistance of vectors to pyrethroid insecticides used to treat ITNs [12][13][14] , and an increase in outdoor vector biting 14 .…”

Section: Introductionmentioning

confidence: 99%

Risk of Plasmodium falciparum infection in south-west Burkina Faso - potential impact of expanding eligibility for seasonal malaria chemoprevention

Yaro

Tiono

Ouédraogo

et al. 2021

Preprint

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Background Burkina Faso has one of the highest malaria burdens in sub-Saharan Africa despite the mass deployment of insecticide-treated nets (ITNs) and use of seasonal malaria chemoprevention (SMC) in children aged up to 5 years. Identification of risk factors for Plasmodium falciparum infection in rural Burkina Faso could help to identify and target malaria control measures. Methods A cross-sectional survey of 1,199 children and adults was conducted during the peak malaria transmission season in south-west Burkina Faso in 2017. Logistic regression was used to identify risk factors for microscopically confirmed P. falciparum infection. A malaria transmission dynamic model was used to determine the impact on malaria cases averted of administering SMC to children aged 5–15 year old. Results P. falciparum prevalence was 32.8% in the study population. Children aged 5 to < 10 years old were at 3.74 times the odds (95% CI = 2.68–5.22, p < 0.001) and children aged 10 to 15 years old at 3.14 times the odds (95% CI = 1.20–8.21, p = 0.02) of P. falciparum infection compared to children aged less than 5 years old. Administration of SMC to children aged up to 10 years is predicted to avert an additional 57 malaria cases per 1000 population per year (9.4% reduction) and administration to children aged up to 15 years would avert an additional 89 malaria cases per 1000 population per year (14.6% reduction) in the Cascades Region, assuming coverage of pyrethroid-piperonyl butoxide ITNs. Conclusion Malaria infections were high in all age strata, although highest in children aged 5 to 15 years, despite roll out of core malaria control interventions. Given the burden of infection in school-age children, extension of the eligibility criteria for SMC could help reduce the burden of malaria in Burkina Faso and other countries in the region.

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Quality Control of Long-Lasting Insecticidal Nets: Are We Neglecting It?

Cited by 25 publications

References 21 publications

Cone Bioassays Provide Reproducible Bioefficacy Estimates with Different Anopheline Mosquitoes and Can Be Used for Quality Assurance of Pyrethroid Insecticide Treated Nets

Cone Bioassays Provide Reproducible Bioefficacy Estimates with Different Anopheline Mosquitoes and Can Be Used for Quality Assurance of Pyrethroid Insecticide Treated Nets

Effect of short-term heating on bioefficacy of deltamethrin-coated long-lasting insecticidal nets

Risk of Plasmodium falciparum infection in south-west Burkina Faso - potential impact of expanding eligibility for seasonal malaria chemoprevention

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