Influence of pyrethroïd-treated bed net on host seeking behavior of Anopheles gambiae s.s. carrying the kdr allele

Porciani, Angélique; Diop, Malal Mamadou; Moiroux, Nicolas; Kadoke-Lambi, Tatiana; Cohuet, Anna; Chandre, Fabrice; Dormont, Laurent; Pennetier, Cédric

doi:10.1371/journal.pone.0164518

Cited by 25 publications

(24 citation statements)

References 44 publications

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“…sinensis populations exposed to long-term insecticide selection pressure. Similarly, altered avoidance behaviour has been described in many other pyrethroid-resistant mosquitoes following contact with pyrethroid-treated bed nets [25–29].…”

Section: Discussionmentioning

confidence: 84%

“…Stimulus-dependent behaviours can also be modified by the selection pressure exerted by long-term insecticide use. The avoidance behaviour of pyrethroid-resistant mosquitoes weakens or disappears following contact with pyrethroid-treated bed nets, leading to significantly altered host-seeking behaviours [25–29]. Both stimulus-dependent and stimulus-independent behaviours have strong effects on host contact by aggressive malaria vectors.…”

Section: Introductionmentioning

confidence: 99%

“…Both stimulus-dependent and stimulus-independent behaviours have strong effects on host contact by aggressive malaria vectors. A change in the response to insecticide-treated surfaces can alter host-seeking behaviour, and thus threaten the effectiveness of indoor vector control tools [8, 29].…”

Section: Introductionmentioning

confidence: 99%

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Modification of contact avoidance behaviour associated with pyrethroid resistance in Anopheles sinensis (Diptera: Culicidae)

Zhang

Shi

et al. 2019

Malar J

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Background Anopheles sinensis is the primary vector of vivax malaria in China and its control is under great threat as the development of insecticide resistance. In contrast to physiological resistance, there is no report of behavioural modifications of resistant An. sinensis after long-term insecticide use, despite their huge potential impact on malaria transmission. Methods Larvae or pupae of An. sinensis were collected from Yuanyang, Bishan, and Wuhe counties from southwestern to eastern China. Resistance to deltamethrin was assayed using the standard World Health Organization (WHO) susceptibility test. The frequency distribution of the kdr allele of the para -type sodium channel gene was determined by polymerase chain reaction (PCR) amplification and DNA sequencing. Contact repellency to deltamethrin-impregnated bed nets was evaluated using a modified WHO cone bioassay. Results All contemporary field populations for all three geographic locations were resistant to deltamethrin, with mortality ranging from 6.00 to 26.79%. Three kdr genotypes with either an L1014F or L1014C substitution with frequencies of 76.10–100% were identified in the Bishan and Wuhe populations, but no kdr mutations were detected in the Yuanyang samples despite high phenotypic resistance. The susceptible mosquitoes exhibited significantly longer flying time and more takeoffs on deltamethrin-treated bed nets (DTN) than on untreated bed nets (UTN), suggestive of robust avoidance behaviour. However, no significant increases in the frequency of takeoffs or flying time were observed in deltamethrin-resistant An. sinensis populations when exposed on DTNs, regardless of the presence of a kdr mutation. Moreover, the first takeoff from DTNs by resistant mosquitoes significantly lagged behind compared to susceptible mosquitoes. Conclusion The An. sinensis populations were highly resistant to deltamethrin and exhibited decreased avoidance behaviour. Behavioural modification significantly associated with deltamethrin resistance, but not directly related to the presence of kdr mutations, indicating that there are additional factors contributing to the changes.

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Section: Discussionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

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Modification of contact avoidance behaviour associated with pyrethroid resistance in Anopheles sinensis (Diptera: Culicidae)

Zhang

Shi

et al. 2019

Malar J

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“…The quantitative loss of community effect by not introducing an insecticide in an insecticide susceptible population is not presently known, and in the face of the current widespread insecticide resistance this loss may even be negligible. Moreover, evidence suggest that hosts under an LLIN could be more attractive to resistant mosquitoes (kdr homozygous) than those sleeping under an untreated net [28]. A randomized controlled trial could tease out the role of the barrier versus the role of the insecticide(s).…”

Section: Could Insecticide-free Nets Still Protect the Community?mentioning

confidence: 99%

Taking the ‘I’ out of LLINs: using insecticides in vector control tools other than long-lasting nets to fight malaria

Paaijmans

Huijben

2020

Malar J

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Long-lasting insecticidal nets, or LLINs, have significantly reduced malaria morbidity and mortality over the past two decades. The net provides a physical barrier that decreases human-mosquito contact and the impregnated insecticide kills susceptible mosquito vectors upon contact and may repel them. However, the future of LLINs is threatened as resistance to pyrethroids is now widespread, the chemical arsenal for LLINs is very limited, time from discovery of next-generation insecticides to market is long, and persistent transmission is frequently caused by vector populations avoiding contact with LLINs. Here we ask the question whether, given these challenges, insecticides should be incorporated in nets at all. We argue that developing long-lasting nets without insecticide(s) can still reduce vector populations and provide both personal and community protection, if combined with other approaches or technologies. Taking the insecticide out of the equation (i) allows for a faster response to the current pyrethroid resistance crisis, (ii) avoids an LLIN-treadmill aimed at replacing failing bed nets due to insecticide resistance, and (iii) permits the utilization of our current and future insecticidal arsenal for other vector control tools to target persistent malaria transmission.

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“…Knockdown resistance (kdr) mechanism is associated with reduced irritant effects of pyrethroids, implying that resistant mosquitoes tend to search longer to feed, remain in contact with treated surfaces longer before taking off and acquire more insecticide through contact. This may result in a total dose picked up to be high enough to kill even homozygous kdr resistant mosquitoes [20,21,22]. On the other hand, mosquitoes with metabolic resistance mechanisms may detoxify the insecticides faster than susceptible mosquitoes and while this is advantageous for survival, resistance is often thought to be associated with fitness costs to the insect [23].…”

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confidence: 99%

Determination of the amount of insecticide picked up by mosquitoes from treated nets

Kristan

Lines

Kaur

2020

Preprint

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Background: Insecticides used in vector control mostly rely on vectors being exposed through contact with treated surfaces, yet little is known about the amount picked up by the insect. Measuring this amount is relevant not only for determining the actual doses that are lethal to the mosquito, but also for understanding effects on the physiology and vector competence of mosquitoes. Insecticides at sub-lethal doses can affect both parasites developing inside mosquitoes and mosquito microbiota, hence it is important to understand the processes by which parasites are exposed to insecticide inside the insect. These doses will inevitably depend on the amount of insecticide that mosquitoes pick up when they come into contact with treated nets. Methods: Three to five days old non-blood fed female Anopheles coluzzii mosquitoes were exposed to a long-lasting insecticidal net (PermaNet 2.0 containing 55 mg/m2 deltamethrin), using a wire ball frame, for 0.5-5.0 minutes. Our in-house developed colorimetric test was used to visually detect the amount of deltamethrin on different parts of the mosquito (legs, heads, thoraxes, abdomens) following exposure to the net. The amount of insecticide picked up by mosquitoes from the net over a range of exposure times was measured using a high-performance liquid chromatography with diode array detection (HPLC-DAD). Results: The colorimetric test, designed to only detect the type 2 pyrethroids (i.e deltamethrin, α-cypermethrin and λ-cyhalothrin) on fabrics (e.g. ITNs) and sprayed walls, was successfully used for the first time to detect deltamethrin on mosquitoes following exposure to the net. The confirmatory HPLC-DAD analysis determined that after 2 min exposure up to 12 ng of deltamethrin adhered to mosquitoes following exposure to PermaNet 2.0 (mean = 5.2 ng/mosquito, SE = 1.9) and that the final dose depends on the length of exposure time. Conclusions: This study demonstrated the potential of a screening (type 2 pyrethroid colorimetric test) and a confirmatory test (HPLC-DAD) to determine the amount of insecticide that adheres to mosquitoes on contact with treated surfaces. This has implications for a precise lethal dose determination and detection of specific insecticide that causes the greatest mosquito mortality in circumstances where mixtures of insecticides may be used to maximise effectiveness of interventions.

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Influence of pyrethroïd-treated bed net on host seeking behavior of Anopheles gambiae s.s. carrying the kdr allele

Cited by 25 publications

References 44 publications

Modification of contact avoidance behaviour associated with pyrethroid resistance in Anopheles sinensis (Diptera: Culicidae)

Modification of contact avoidance behaviour associated with pyrethroid resistance in Anopheles sinensis (Diptera: Culicidae)

Taking the ‘I’ out of LLINs: using insecticides in vector control tools other than long-lasting nets to fight malaria

Determination of the amount of insecticide picked up by mosquitoes from treated nets

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