scholarly journals Efficacy of Long-lasting Insecticidal Nets With Declining Physical and Chemical Integrity on Aedes aegypti (Diptera: Culicidae)

2019 ◽  
Author(s):  
Josué Herrera-Bojórquez ◽  
Emilio Trujillo-Peña ◽  
José Vadillo-Sánchez ◽  
Martin Riestra-Morales ◽  
Azael Che-Mendoza ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Residual Activity ◽  
Blood Feeding ◽  
Chemical Effect ◽  
Feeding Inhibition ◽  
Mosquito Mortality ◽  
Field Deployment ◽  
Deployment Time ◽  
Long Lasting Insecticidal Nets ◽  
Over Time

Abstract Fitting long-lasting insecticidal nets (LLIN) as screens on doors/windows has a significant impact on indoor-adult Aedes aegypti (L.), with entomological reductions measured in a previous study being significant for up to 2 yr post-installation, even in the presence of pyrethroid-resistant Aedes populations. To better understand the mode of LLIN protection, bioassays were performed to evaluate the effects of field deployment (0, 6, and 12 mo) and damage type (none, central, lateral, and multiple) on LLIN efficacy. Contact bioassays confirmed that LLIN residual activity (median knockdown time, in minutes, or MKDT) decreased significantly over time: 6.95 (95% confidence interval [CI]: 5.32–8.58) to 9.24 (95% CI: 8.69–9.79) MKDT at 0- and 12-mo age, respectively, using a pyrethroid-susceptible Aedes strain. Tunnel tests (exposing human forearm for 40 min as attractant) showed that deployment time affected negatively Aedes passage inhibition from 54.9% (95% CI: 43.5–66.2) at 0 mo to 35.7% (95% CI: 16.3–55.1) at 12 mo and blood-feeding inhibition from 65.2% (95% CI: 54.2–76.2) to 48.9% (95% CI: 26.4–71.3), respectively; both the passage/blood-feeding inhibition increased by a factor of 1.8–2.9 on LLINs with multiple and central damages compared with nets with lateral damage. Mosquito mortality was 74.6% (95% CI: 65.3–83.9) at 0 mo, 72.3% (95% CI: 64.1–80.5) at 6 mo, and 59% (95% CI: 46.7–71.3) at 12 mo. Despite the LLIN physical integrity could be compromised over time, we demonstrate that the remaining chemical effect after field conditions would still contribute to killing/repelling mosquitoes.

scholarly journals Bio-efficacy and wash resistance of MAGNet long-lasting insecticidal net against wild populations of Anopheles funestus in experimental huts in Muheza, Tanzania

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Eliningaya J. Kweka ◽  
Patrick K. Tungu ◽  
Aneth M. Mahande ◽  
Humphrey D. Mazigo ◽  
Subira Sayumwe ◽  
...  
Keyword(s):  
Anopheles Funestus ◽  
Blood Feeding ◽  
Personal Protection ◽  
Feeding Rates ◽  
Feeding Inhibition ◽  
Experimental Huts ◽  
Host Seeking ◽  
Mosquito Mortality ◽  
Resistant Population ◽  
Long Lasting Insecticidal Nets

Abstract Background The decline in malaria cases and vectors is major milestone in fighting against malaria. The efficacy of MAGNet long-lasting insecticidal nets (MAGNet LLIN), an alpha-cypermethrin incorporated long-lasting net, with the target dose ± 25% of 5.8 g active ingredient (AI)/kg (4.35–7.25 g AI/kg) was evaluated in six veranda-trap experimental huts in Muheza, Tanzania against freely flying wild population of Anopheles funestus. Methods MAGNet LLINs were tested against wild, free-flying, host-seeking An. funestus mosquitoes over a period of 6 weeks (total of 36 nights in the huts). MAGNet LLIN efficacy was determined in terms of mosquito mortality, blood-feeding inhibition, deterrence, induced exiting, personal protection, and insecticidal killing over 20 washes according to WHO standardized procedures. Efficacy was compared with reference to a WHOPES recommended approved LLINs (DuraNet) and to a net conventionally treated (CTN) treated with alpha-cypermethrin at WHO-recommended dose and washed to just before cut-off point. The efficacy of MAGNet was evaluated in experimental huts against wild, free-flying, pyrethroid-resistant An. funestus. The WHO-susceptibility method was used to detect resistance in wild Anopheles exposed to 0.75% permethrin. Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets and standard LLINs. Blood-feeding rates were recorded and compared between the 20 times washed; blood-feeding rates between 20 times washed MAGNet LLIN and 20 times washed WHOPES-approved piperonyl butoxide (PBO)/pyrethroid were not statistically different (p > 0.05). Results The results have evidently shown that MAGNet LLIN provides similar blood-feeding inhibition, exophily, mortality, and deterrence to the standard approved LLIN, thus meeting the WHOPES criteria for blood feeding. The significantly high feeding inhibition and personal protection over pyrethroid-resistant An. funestus recorded by both unwashed and 20 times washed MAGNet compared to the unwashed DuraNet, the WHOPES-approved standard pyrethroid-only LLIN provides proof of MAGNet meeting Phase II WHOPES criteria for a LLIN. Conclusion Based on this study, MAGNet has been shown to have a promising impact on protection when 20 times washed against a highly resistant population of An. funestus.

scholarly journals Long-lasting insecticidal nets retain bio-efficacy after five years of storage: implications for malaria control programmes 

2020 ◽  
Author(s):  
Jeremiah John Musa ◽  
Sarah Moore ◽  
Jason Moore ◽  
Emmanuel Mbuba ◽  
Edgar Mbeyela ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Malaria Control ◽  
Blood Feeding ◽  
Sensu Stricto ◽  
World Health ◽  
Small Scale ◽  
Feeding Inhibition ◽  
Control Programmes ◽  
Endemic Areas ◽  
Long Lasting Insecticidal Nets

Abstract Background: Long-lasting insecticidal nets (LLINs) are the most sustainable and effective malaria control tool currently available. Global targets are for 80% of the population living in malaria endemic areas to have access to (own) and use a LLIN. However, current access to LLINs in endemic areas is 56% due to system inefficiencies and budget limitations. Thus, cost-effective approaches to maximize access to effective LLINs in endemic areas are required. This study evaluated whether LLINs that had been stored for five years under manufacturer’s recommended conditions may be optimally effective against Anopheles mosquitoes, to inform malaria control programmes and governments on the periods over which LLINs may be stored between distributions, in an effort to maximize use of available LLINs. Methods: Standard World Health Organization (WHO) bioassays (cone and tunnel test) were used to evaluate the bio-efficacy and wash resistance of Olyset® and DawaPlus® 2.0 (rebranded Tsara® Soft) LLINs after five years of storage at 25°C to 33.4°C and 40% to 100% relative humidity. In addition, a small scale Ifakara Ambient Chamber test (I-ACT) was conducted to compare the bio-efficacy of one long stored LLINs to one new LLIN of the same brand, washed or unwashed. LLINs were evaluated using laboratory reared fully susceptible Anopheles gambiae sensu stricto (s.s.) (Ifakara strain) and pyrethroid resistant Anopheles arabiensis (Kingani strain). Results: After five years of storage, both unwashed and washed, Olyset® and DawaPlus® 2.0 (Tsara® Soft) LLINs passed WHO bio-efficacy criteria on knockdown (KD60) ≥95%, 24-hour mortality ≥80% and ≥90% blood-feeding inhibition in WHO assays against susceptible An. gambiae s.s. DawaPlus® 2.0 LLINs also passed combined WHO bioassay criteria against resistant An. arabiensis. Confirmatory I-ACT tests using whole nets demonstrated that long-stored LLINs showed higher efficacy than new LLINs on both feeding inhibition and mortality endpoints against resistant strains.Conclusions: Even after long-term storage of around 5 years, both Olyset® and DawaPlus® 2.0 LLINs remain efficacious against susceptible Anopheles mosquitoes at optimal storage range of 25°C to 33.4°C for temperature and 40% to 100% relative humidity measured by standard WHO methods. DawaPlus® 2.0 (Tsara® Soft) remained efficacious against resistant strain.

scholarly journals Efficacy of indoor residual spraying with broflanilide (TENEBENAL), a novel meta-diamide insecticide, against pyrethroid-resistant anopheline vectors in northern Tanzania: An experimental hut trial

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0248026
Author(s):  
Janneke Snetselaar ◽  
Mark W. Rowland ◽  
Baltazari J. Manunda ◽  
Ezekia M. Kisengwa ◽  
Graham J. Small ◽  
...  
Keyword(s):  
Residual Activity ◽  
Indoor Residual Spraying ◽  
Concrete Surface ◽  
Blood Feeding ◽  
Cross Resistance ◽  
Feeding Inhibition ◽  
Experimental Hut ◽  
Northern Tanzania ◽  
Residual Efficacy ◽  
Diamide Insecticide

Novel chemistry for vector control is urgently needed to counter insecticide resistance in mosquitoes. Here a new meta-diamide insecticide, broflanilide (TENEBENALTM), was evaluated in East African experimental huts in Moshi, northern Tanzania. Two consecutive experimental hut trials with broflanilide 50WP were conducted; the first evaluating the efficacy of three concentrations, 50 mg/m2, 100 mg/m2, and 200 mg/m2 using a prototype formulation, and the second trial evaluating an improved formulation. The IRS treatments were applied on both mud and concrete surfaces and efficacy was monitored over time. The mortality, blood-feeding inhibition and exiting behaviour of free-flying wild mosquitoes was compared between treatment arms. Additionally, cone assays with pyrethroid-susceptible and resistant mosquito strains were conducted in the huts to determine residual efficacy. The first trial showed a dosage-mortality response of the prototype formulation and 3–8 months of residual activity, with longer activity on concrete than mud. The second trial with an improved formulation showed prolonged residual efficacy of the 100 mg/m2 concentration to 5–6 months on mud, and mosquito mortality on the concrete surface ranged between 94–100% for the full duration of the trial. In both trials, results with free-flying, wild Anopheles arabiensis echoed the mortality trend shown in cone assays, with the highest dose inducing the highest mortality and the improved formulation showing increased mortality rates. No blood-feeding inhibition or insecticide-induced exiting effects were observed with broflanilide. Broflanilide 50WP was effective against both susceptible and pyrethroid-resistant mosquito strains, demonstrating an absence of cross resistance between broflanilide and pyrethroids. The improved formulation, which has now been branded VECTRONTM T500, resulted in a prolonged residual efficacy. These results indicate the potential of this insecticide as an addition to the arsenal of IRS products needed to maintain both control of malaria and resistance management of malaria-transmitting mosquitoes.

The First GLP Compliant Study in Africa for the Evaluation of LLIN’s; Efficacy of SafeNet® and SafeNet NF®

2021 ◽  
Author(s):  
Salum Azizi ◽  
Janneke Snetselaar ◽  
Robert Kaaya ◽  
Johnson Matowo ◽  
Hudson Onen ◽  
...  
Keyword(s):  
Universal Coverage ◽  
Blood Feeding ◽  
World Health ◽  
Manufacturing Cost ◽  
Feeding Inhibition ◽  
Evaluation Scheme ◽  
Residual Efficacy ◽  
Good Laboratory ◽  
Health Organization ◽  
Long Lasting Insecticidal Nets

Abstract Background: To attain and sustain the universal Long-Lasting Insecticidal Nets (LLINs) coverage, cheap nets that provides equivalent or better protection than the standard LLINs, are required. While it is essential to follow the World Health Organization (WHO) guidelines for the evaluation of LLINs, adherence to the Good Laboratory Practice (GLP) is necessary to generate reliable and reproducible data that will facilitate efficient LLINs to be speedy registered. Adherence to GLP obviate the need to duplicate the assessment and ensures substandard LLINs are not reaching the market. This study aimed to evaluate efficacy of SafeNet NF® and SafeNet® LLIN in accordance to the WHO Pest Evaluation Scheme (WHOPES) and the GLP guidelines. Both candidate LLINs were manufactured with less fabrics to cut down manufacturing costs, motivated by the need for cheaper LLINs to achieve universal coverage. Materials & Methods: SafeNet NF® and SafeNet® LLIN, were assessed in experimental huts against wild, pyrethroid-resistant Anopheles arabiensis mosquitoes. Efficacy in terms of mosquito blood-feeding inhibition and mortality, was compared with Interceptor® LLIN and an untreated net. All nets were washed and artificially holed to simulate a used torn net. The GLP guidelines were followed throughout this study.Results: The mortality of mosquitoes exposed to SafeNet NF® and SafeNet® LLIN were equivalent to that of the reference net. Blood-feeding inhibition was only evident in Interceptor® LLIN. Adherence to GLP was observed throughout the study.Conclusions: Step-wise procedures to conduct LLIN evaluation in compliance to both WHOPES and GLP guidelines are elaborated in this study. SafeNet NF® and SafeNet® LLIN offers equivalent protection as Interceptor® LLIN and can facilitate universal LLIN coverage due to its low manufacturing cost. However, further research is needed to understand durability, acceptability and residual efficacy of these nets in field environments.

scholarly journals Long-Lasting Insecticidal Nets retain bio-efficacy after five years of storage: implications for malaria control programmes

2019 ◽  
Author(s):  
Jeremiah John Musa ◽  
Sarah Moore ◽  
Jason Moore ◽  
Emmanuel Mbuba ◽  
Edgar Mbeyela ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Malaria Control ◽  
Blood Feeding ◽  
World Health ◽  
Small Scale ◽  
Anopheles Gambiae S.S ◽  
Feeding Inhibition ◽  
Anopheles Mosquitoes ◽  
Endemic Areas ◽  
Long Lasting Insecticidal Nets

Abstract Background: Long Lasting Insecticidal Nets (LLINs) are the most sustainable and effective malaria control tool currently available. Global targets are for 80% of the population living in malaria endemic areas to have access to (own) and use a LLIN. However, current access to LLINs in endemic areas is 56% due to system inefficiencies and budget limitations. Thus, cost-effective approaches to maximize access of effective LLINs in endemic areas are required. This study evaluated whether LLINs that had been stored for five years under manufacturer’s recommended conditions may be optimally effective against Anopheles mosquitoes, to inform malaria control programs and governments on the periods over which LLINs may be stored between distributions, in an effort to maximise use of available LLINs. Methods: Standard World Health Organization (WHO) bioassays (cone and tunnel test) were used to evaluate the bio-efficacy and wash resistance of Olyset® and DawaPlus® 2.0 (rebranded Tsara® Soft) LLINs after five years of storage at 25°C - 33.4°C and 40% - 100% relative humidity. In addition a small scale, Ifakara Ambient Chamber tests (I-ACT) were conducted to compare the bio-efficacy of one long stored LLINs to one new LLIN of the same brand, washed or unwashed. LLINs were evaluated using laboratory reared fully susceptible Anopheles gambiae s.s. (Ifakara) and pyrethroid resistant Anopheles arabiensis (Kingani). Results: After five years of storage, both unwashed and washed, Olyset® and DawaPlus® 2.0 LLINs passed WHO bio-efficacy criteria on knockdown (KD60) ≥95%, 24-hour mortality ≥80% and ≥90% blood-feeding inhibition in WHO assays against susceptible An. gambiae s.s. DawaPlus® 2.0 LLINs also passed combined WHO bioassay criteria against resistant An. arabiensis. Confirmatory I-ACT tests using whole nets demonstrated that long stored LLINs showed higher efficacy than new LLINs on both feeding inhibition and mortality endpoints against resistant strains. Conclusions: Even after long-term storage of around 5 years, Olyset® and DawaPlus® 2.0 LLINs remain efficacious against susceptible Anopheles mosquitoes at optimal storage range of 25°C - 33.4°C for temperature and 40% - 100% relative humidity measured by standard WHO methods.

scholarly journals Assessing the impact of low-technology emanators alongside long-lasting insecticidal nets to control malaria

2020 ◽  
Vol 376 (1818) ◽  
pp. 20190817 ◽  
Author(s):  
Joel Hellewell ◽  
Ellie Sherrard-Smith ◽  
Sheila Ogoma ◽  
Thomas S. Churcher
Keyword(s):  
Disease Transmission ◽  
Pyrethroid Resistance ◽  
Control Strategies ◽  
Indoor Residual Spraying ◽  
Additional Benefit ◽  
Sub Saharan Africa ◽  
Outdoor Biting ◽  
Mosquito Mortality ◽  
The Impact ◽  
Long Lasting Insecticidal Nets

Malaria control in sub-Saharan Africa relies on the widespread use of long-lasting insecticidal nets (LLINs) or the indoor residual spraying of insecticide. Disease transmission may be maintained even when these indoor interventions are universally used as some mosquitoes will bite in the early morning and evening when people are outside. As countries seek to eliminate malaria, they can target outdoor biting using new vector control tools such as spatial repellent emanators, which emit airborne insecticide to form a protective area around the user. Field data are used to incorporate a low-technology emanator into a mathematical model of malaria transmission to predict its public health impact across a range of scenarios. Targeting outdoor biting by repeatedly distributing emanators alongside LLINs increases the chance of elimination, but the additional benefit depends on the level of anthropophagy in the local mosquito population, emanator effectiveness and the pre-intervention proportion of mosquitoes biting outdoors. High proportions of pyrethroid-resistant mosquitoes diminish LLIN impact because of reduced mosquito mortality. When mosquitoes are highly anthropophagic, this reduced mortality leads to more outdoor biting and a reduced additional benefit of emanators, even if emanators are assumed to retain their effectiveness in the presence of pyrethroid resistance. Different target product profiles are examined, which show the extra epidemiological benefits of spatial repellents that induce mosquito mortality. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases’.

scholarly journals Exploring alternative insecticide delivery options in a “Lethal House Lure” for malaria vector control

2021 ◽  
Author(s):  
Welbeck A. Oumbouke ◽  
Antoine M.G. Barreaux ◽  
Innocent T. Zran ◽  
Alphonsine A. Koffi ◽  
Yao N’Guessan ◽  
...  
Keyword(s):  
Controlled Trial ◽  
Residual Activity ◽  
Alternative Methods ◽  
Malaria Vector Control ◽  
Rapid Decline ◽  
Mosquito Mortality ◽  
Delivery Options ◽  
Control Technologies ◽  
Cluster Randomized ◽  
The Impact

Abstract The In2Care® EaveTube is a house modification designed to block and kill malaria mosquitoes using an electrostatic netting treated with insecticide powder. A previous study demonstrated prolonged duration of effective action of insecticide-treated electrostatic netting in a semi-field setting. As part of a cluster randomized controlled trial (CRT) of the EaveTube intervention in Cote d’Ivoire, we investigated the residual efficacy of a pyrethroid insecticide deployed in Eave Tubes under village condition of use. We also explored the scope of using existing malaria control technologies including LLINs and IRS as alternative methods to deliver insecticides in the lethal house lure. The efficacy of beta-cyfluthrin was evaluated using the “eave tube bioassay” and was found to be relatively short-lived in the field during the CRT, with mortality of pyrethroid resistant Anopheles gambiae mosquitoes declining below 80% after 4 months. The impact (mosquito mortality) of PVC tubes coated with pirimiphos methyl was similar to that of beta-cyfluthrin treated insert (66.8 vs 62.8%) in release-recapture experiments in experimental huts. Efficacy was significantly lower with all the LLINs tested; however, the roof of PermaNet 3.0 induced significantly higher mosquito mortality (50.4%) compared to Olyset Plus (25.9%) and Interceptor G2 (21.6%) LLINs. The new delivery methods showed a rapid decline in efficacy over time with mortality decreasing below 50% within 2 months in residual activity bioassays. None of the current products appeared superior to the powder treatments but as with the powders, further research and development on formulations and doses are required.

scholarly journals The efficacy of insecticide-treated window screens and eaves against Anopheles mosquitoes: a scoping review

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Beverly I. Anaele ◽  
Karan Varshney ◽  
Francis S. O. Ugwu ◽  
Rosemary Frasso
Keyword(s):  
Scoping Review ◽  
Protective Efficacy ◽  
Blood Feeding ◽  
Bed Nets ◽  
Anopheles Mosquitoes ◽  
Mosquito Mortality ◽  
Binding Agents ◽  
Pirimiphos Methyl ◽  
Mosquito Entry ◽  
Is Value

Abstract Background Female mosquitoes serve as vectors for a host of illnesses, including malaria, spread by the Plasmodium parasite. Despite monumental strides to reduce this disease burden through tools such as bed nets, the rate of these gains is slowing. Ongoing disruptions related to the COVID-19 pandemic may also negatively impact gains. The following scoping review was conducted to examine novel means of reversing this trend by exploring the efficacy of insecticide-treated window screens or eaves to reduce Anopheles mosquito bites, mosquito house entry, and density. Methods Two reviewers independently searched PubMed, Scopus, and ProQuest databases on 10 July, 2020 for peer-reviewed studies using insecticide-treated screens or eaves in malaria-endemic countries. These articles were published in English between the years 2000–2020. Upon collection, the reports were stratified into categories of biting incidence and protective efficacy, mosquito entry and density, and mosquito mortality. Results Thirteen out of 2180 articles were included in the final review. Eaves treated with beta-cyfluthrin, transfluthrin or bendiocarb insecticides were found to produce vast drops in blood-feeding, biting or mosquito prevalence. Transfluthrin-treated eaves were reported to have greater efficacy at reducing mosquito biting: Rates dropped by 100% both indoors and outdoors under eave ribbon treatments of 0.2% transfluthrin (95% CI 0.00–0.00; p < 0.001). Additionally, co-treating window screens and eaves with polyacrylate-binding agents and with pirimiphos-methyl has been shown to retain insecticidal potency after several washes, with a mosquito mortality rate of 94% after 20 washes (95% CI 0.74–0.98; p < 0.001). Conclusions The results from this scoping review suggest that there is value in implementing treated eave tubes or window screens. More data are needed to study the longevity of screens and household attitudes toward these interventions.

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