Do holes in long-lasting insecticidal nets compromise their efficacy against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus? Results from a release–recapture study in experimental huts

Randriamaherijaona, Sanjiarizaha; Briët, Olivier J. T.; Boyer, Sébastien; Bouraïma, Aziz; N’Guessan, Raphaël; Rogier, Christophe; Corbel, Vincent

doi:10.1186/s12936-015-0836-7

Cited by 30 publications

(33 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Though useful, this entomological measure should not be considered as a measure of the effectiveness of pyrethroid LLINs. The personal protection provided by sleeping under an LLIN is likely to be substantial even at very high levels of resistance ( Strode et al, 2014 ; Randriamaherijaona et al, 2015 ). Any reduction in mosquito mortality will likely reduce the community impact of LLINs though it may be hard to detect, especially in areas with new LLINs (the public health impact of resistance is likely to be greater in older nets, Figure 3E ).…”

Section: Discussionmentioning

confidence: 99%

The impact of pyrethroid resistance on the efficacy and effectiveness of bednets for malaria control in Africa

Churcher

Lissenden

Griffin

et al. 2016

eLife

241

254

View full text Add to dashboard Cite

Long lasting pyrethroid treated bednets are the most important tool for preventing malaria. Pyrethroid resistant Anopheline mosquitoes are now ubiquitous in Africa, though the public health impact remains unclear, impeding the deployment of more expensive nets. Meta-analyses of bioassay studies and experimental hut trials are used to characterise how pyrethroid resistance changes the efficacy of standard bednets, and those containing the synergist piperonyl butoxide (PBO), and assess its impact on malaria control. New bednets provide substantial personal protection until high levels of resistance, though protection may wane faster against more resistant mosquito populations as nets age. Transmission dynamics models indicate that even low levels of resistance would increase the incidence of malaria due to reduced mosquito mortality and lower overall community protection over the life-time of the net. Switching to PBO bednets could avert up to 0.5 clinical cases per person per year in some resistance scenarios.DOI: http://dx.doi.org/10.7554/eLife.16090.001

show abstract

Section: Discussionmentioning

confidence: 99%

The impact of pyrethroid resistance on the efficacy and effectiveness of bednets for malaria control in Africa

Churcher

Lissenden

Griffin

et al. 2016

eLife

241

254

View full text Add to dashboard Cite

show abstract

“…Despite insecticide effects, it has been shown experimentally that people sleeping under holed treated nets may be bitten by insecticide-susceptible mosquitoes even though the mosquitoes are eventually killed by net contact (e.g. [ 16 , 17 ]).…”

Section: Discussionmentioning

confidence: 99%

How many holes is too many? A prototype tool for estimating mosquito entry risk into damaged bed nets

Sutcliffe

Yin

2017

Malar J

View full text Add to dashboard Cite

BackgroundInsecticide-treated bed nets (ITNs) have played an integral role in malaria reduction but how insecticide depletion and accumulating physical damage affect ITN performance is poorly understood. More accurate methods are needed to assess damage to bed nets so that they can be designed, deployed and replaced optimally.MethodsVideo recordings of female Anopheles gambiae in near approach (1–½ cm) to occupied untreated rectangular bed nets in a laboratory study were used to quantify the amount of mosquito activity (appearances over time) around different parts of the net, the per-appearance probability of a mosquito coming close to holes of different sizes (hole encounter) and the per-encounter probability of mosquitoes passing through holes of different sizes (hole passage).ResultsAppearance frequency on different parts of the net reflected previously reported patterns: the area of the net under greatest mosquito pressure was the roof, followed by the bottom 30 cm of the sides, followed by the 30 cm area immediately above this, followed by the upper two-thirds of the sides. The ratio of activity in these areas was (respectively) 250:33:5:1. Per-appearance probability of hole encounter on all parts of the net was strongly predicted by a factor combining hole perimeter and area. Per-encounter probability of hole passage, in turn, was strongly predicted by hole width. For a given width, there was a 20% greater risk of passage through holes on the roof than holes on the sides.DiscussionAppearance, encounter and passage predictors correspond to various mosquito behaviours that have previously been described and are combined into a prototype mosquito entry risk tool that predicts mosquito entry rates for nets with various amounts of damage. Scenarios that use the entry risk tool to test the recommendations of the WHOPES proportionate hole index (pHI) suggest that the pHI hole size categories and failure to account for hole location likely sometimes lead to incorrect conclusions about net serviceability that could be avoided by using an entry risk tool of the form presented here instead. Practical methods of collecting hole position, shape and size information for bed net assessments using the tool in the field are discussed and include using image analysis and on-line geometric analysis tools.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-017-1951-4) contains supplementary material, which is available to authorized users.

show abstract

“…Over time, nets become torn with repeated use. While the inclusion of pyrethroid insecticides helps to prevent mosquitoes entering nets to some extent [33], the more holes in a net, the more mosquitoes will enter the net and reduce the protection given to a net user [34]. It is important to understand how much of the net surface area is available for mosquitoes to pass through.…”

Section: Itn Physical Degradation (Serviceability)mentioning

confidence: 99%

The Consequences of Declining Population Access to Insecticide Treated Nets (ITNs) on Net Use Patterns and Physical Degradation of Nets after 22 Months of Ownership

Mboma

Festo

Lorenz

et al. 2020

Preprint

View full text Add to dashboard Cite

BackgroundAs the number of insecticide-treated nets (ITNs) in households (access) declines when nets wear out some household-members are prioritised to use the remaining ITNs. This study assessed how nets are allocated within households to individuals of different age categories as ITNs are lost or damaged and as new ITNs are obtained. The study also explored how ITN allocation affects ITN durability. MethodsA cross-sectional household survey and ITN durability study was conducted among 2,875 households across Tanzania to determine the proportion of nets that remain protective (serviceable) twenty-two months after net distribution aiming for universal coverage. Allocation of study nets within houses and re-allocation of ITNs when new Universal Replacement Campaign (URC) nets arrived in study households in Musoma District was also assessed.ResultsOnly 57.0% [95% CI: 53.9-60.1%] of households had enough ITNs for every household member (assuming one net covers every 2 members). In households with enough nets, 77.5% of members slept under ITNs. In households without enough nets, pregnant women (54.6%), children<5 (45.8%) and adults (42.1%) were prioritised, with fewer school-age children 5-14 (35.9%), youths 15-24 (28.1%) and seniors>65 (32.6%) sleeping under ITNs. Crowding ( 3 people slept under nets) was twice as common among people residing in houses without enough nets for all age groups apart from children<5. Nets were less likely to be serviceable if 3 people slept under them (OR=0.50 [95%CI 0.40-0.63]); if nets were used by school-age children (OR=0.72 [95%CI 0.56-0.93]) and if the net product was Olyset®. One month after the URC, only 23.6% [95%CI 16.7-30.6%] had access to an URC ITN in Musoma district. Householders in Musoma district continued the use of old ITNs even with the arrival of new URC nets.ConclusionUsers determined the useful life of ITNs and prioritized pregnant women and children<5 to serviceable ITNs. When household net access declines, users adjust by crowding under remaining nets, which further reduces ITN lifespan. School-age children that commonly harbour gametocytes that mediate malaria transmission are compelled to sleep under unserviceable nets, crowd under nets or remain uncovered. However, they were accommodated by the arrival of new nets. More frequent ITN delivery through the school-net program in combination with mass distribution campaigns is essential to maximise ITN effectiveness.

show abstract

Do holes in long-lasting insecticidal nets compromise their efficacy against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus? Results from a release–recapture study in experimental huts

Cited by 30 publications

References 48 publications

The impact of pyrethroid resistance on the efficacy and effectiveness of bednets for malaria control in Africa

The impact of pyrethroid resistance on the efficacy and effectiveness of bednets for malaria control in Africa

How many holes is too many? A prototype tool for estimating mosquito entry risk into damaged bed nets

The Consequences of Declining Population Access to Insecticide Treated Nets (ITNs) on Net Use Patterns and Physical Degradation of Nets after 22 Months of Ownership

Contact Info

Product

Resources

About