Pyrethroid-treated bed nets impair blood feeding performance in insecticide resistant mosquitoes

Barreaux, Priscille; Ranson, Hilary; Foster, Geraldine M.; McCall, Philip

doi:10.1038/s41598-023-35958-z

Cited by 7 publications

(4 citation statements)

References 52 publications

(61 reference statements)

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“…Finally. as observed by other studies [44][45][46][47][48][49] pyrethroid-only nets still provided some protection in this area of pyrethroid resistance. Non-users of nets in clusters where chlorfenapyr-pyrethroid nets were used were better protected than non-users in clusters where pyrethroid only nets were used, but even the more effective nets did not adequately control malaria and infection prevalence was still very high even amongst users of these nets.…”

Section: Discussionsupporting

confidence: 78%

Community benefits of mass distribution of three types of dual-active-ingredient long-lasting insecticidal nets against malaria prevalence in Tanzania: evidence from a 3-year cluster-randomized controlled trial

Lukole,

Cook,

Mosha

et al. 2024

Preprint

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Background Long-lasting insecticidal nets (LLINs) were once fully effective for the prevention of malaria; however, mosquitoes have developed resistance to pyrethroids, the main class of insecticides used on nets. Dual active ingredient LLINs (dual-AI LLINs) have been rolled out as an alternative to pyrethroid (PY)-only LLINs to counteract this. Understanding the minimum community usage at which these novel nets generate an effect that also benefits non-net users against malaria infection is vital for planning net distribution strategies and mobilization campaigns. Methods We conducted a secondary analysis of a 3-year randomized controlled trial (RCT) in 84 clusters in North-western Tanzania to evaluate the effectiveness of three dual-AI LLINs: pyriproxyfen and alpha(α)-cypermethrin (pyriproxyfen-PY), chlorfenapyr and α-cypermethrin (chlorfenapyr-PY), and the synergist piperonyl-butoxide and permethrin (PBO-PY) compared to α-cypermethrin only nets (PY-only). We measured malaria infection prevalence using 5 cross-sectional surveys between 2020 and 2022. We assessed net usage at the cluster level and malaria infection in up to two children aged between 6 months and 14 years in 45 households per cluster and compared infection prevalence between net users and non-users with the different net types and usage levels. Findings A total of 22,479 children from 12,654 households were tested for malaria using rapid diagnostic tests in January 2020, 2021, & 2022 and July 2020 & 2021. In all surveys combined, 23% (5,062/22,479) of children reported not using a net the night before the surveys. The proportion of non-net users was highest in the later surveys. Across all study arms and at each time point, users of nets had significantly lower malaria infection than non-users. Overall, malaria prevalence was 52% (2649/5062) among non-net users and 32% (5572/11845) among users (of any net). Among non-net users, community-level usage of >40% of dual-AI LLIN was significantly associated with protection against malaria infection: chlorfenapyr-PY (OR: 0.44 (95% CI: 0.27-0.71), p=0.0009), PBO-PY (OR: 0.55 (95% CI: 0.33-0.94), p=0.0277) and pyriproxyfen-PY (OR: 0.61 (95% CI: 0.37-0.99), p=0.0470) compared with non-users in clusters with >40% usage of PY-only LLINs. There was weak evidence of protection against malaria infection to non-net users in the chlorfenapyr-PY arm when community-level usage was ≤40% (OR: 0.65 (95% CI: 0.42-1.01), p=0.0528) compared to those living in clusters with >40% usage of pyrethroid-only LLINs. The study was limited to non-users which were defined as participants who did not sleep under any net the night before. This might not capture occasional net usage during the week. Conclusion Our study demonstrated that at a community usage of 40% or more of dual-AI LLINs, non-net users benefited from the presence of these nets. Noticeably, even when usage was ≤40% in the chlorfenapyr-PY arm, non-users were better protected than non-users in the higher coverage PY-only arm. The greater difference in malaria risk observed between users and non-users across all study arms indicates that nets play a crucial role in providing personal protection against malaria infection for the people using the net and that net usage needs to be maximized to realize the full potential of all nets.

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Section: Discussionsupporting

confidence: 78%

Community benefits of mass distribution of three types of dual-active-ingredient long-lasting insecticidal nets against malaria prevalence in Tanzania: evidence from a 3-year cluster-randomized controlled trial

Lukole,

Cook,

Mosha

et al. 2024

Preprint

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“…Fatou and Müller [24] found that while permethrin-treated nets had no detectable repellent effect on mosquitoes, they elicited a strong irritant response resulting in contact disengagement, allowing both susceptible and resistant forms to pass more easily through holes in treated nets than untreated nets. Barreaux et al [25] recently reported that although the duration of bloodfeeding was significantly reduced when feeding through an ITN, A. gambiae s.l. could compensate by increasing its ingested blood flow rate by 35%.…”

Section: Discussionmentioning

confidence: 99%

“…Barreaux et al . [ 25 ] recently reported that although the duration of bloodfeeding was significantly reduced when feeding through an ITN, A. gambiae s.l. could compensate by increasing its ingested blood flow rate by 35%.…”

Section: Discussionmentioning

confidence: 99%

Video-tracked Anopheles arabiensis entry and exit behaviour at washed and damaged pyrethroid-treated bednets

Parker,

Kakilla,

Nelwin

et al. 2024

R. Soc. Open Sci.

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Insecticide-treated nets (ITNs) are the most effective method for malaria prevention in Africa. Using near-infrared video tracking in a laboratory environment, we recorded and assessed bednet entry and exit by a northern Tanzanian population of Anopheles arabiensis at a human-occupied untreated net and a PermaNet® 2.0 ITN. Both had 12 holes, each 10 cm in diameter, punctured at specific locations, and the ITN was washed 20 times to further simulate the wear and tear of ageing. Washing reduced the insecticide content of ITNs by 61%, which then showed similar rates to the untreated nets for net entry (39% entered untreated net and 41% entered ITN; p = 0.84) and exit (37% and 43%, respectively; p = 0.67). Regardless of treatment, approximately 40% of mosquitoes entered nets within 20 s of first appearing in the field of view and reached the volunteer’s skin within 5 s of entering the net. Mortality rates post-exposure were significantly higher ( p = 0.048) at ITNs (26.6%; 95% CI 13.4%–39.7%) than at untreated controls (6.4%; 95% CI 1.8%–14.6%). The washed and aged ITN provided little additional personal protection for the sleeper over an untreated net. Simple adjustments to materials and design that could extend the effective lifespan of ITNs are discussed.

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“…The latter could trigger an avoidance behaviour in the vectors [ 48 ], affecting their ability to take a blood meal. As a key parameter influencing malaria transmission potential [ 49 ], blood-feeding behaviour observed with new nets could benefit malaria vector control interventions [ 42 – 44 ]. This result confirms that high-dose pyrethroids would continue to play a valuable role in blood-feeding inhibition and personal protection [ 50 ].…”

Section: Discussionmentioning

confidence: 99%

Efficacy of Interceptor G2, Royal Guard and PermaNet 3.0 against pyrethroid-resistant Anopheles gambiae s.l. from Za-Kpota, southern Benin: an experimental hut trial

Sovegnon,

Akoton,

Stopard

et al. 2024

Parasites Vectors

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Background The widespread use of insecticide-treated nets (ITNs) has significantly contributed to the reduction in malaria cases and deaths observed across Africa. Unfortunately, this control strategy is threatened by the rapid spread of pyrethroid resistance in malaria vectors. Dual-active-ingredient insecticidal nets are now available to mitigate the impact of pyrethroid resistance. To facilitate evidence-based decisions regarding product selection in specific use settings, data are needed on the efficacy of these different nets against local mosquito populations. Methods Two experimental hut trials were performed in Za-Kpota, southern Benin in 2021 to evaluate the performance of Interceptor G2 (BASF), Royal Guard (Disease Control Technologies) and PermaNet 3.0 (Vestergaard Frandsen), all dual-active-ingredient bednets, in comparison to untreated or standard pyrethroid-treated bednets, against free-flying wild Anopheles gambiae mosquitoes. The performance of some of these next-generation nets was compared to the same type of nets that have been in use for up to 2 years. Mosquitoes collected in the huts were followed up after exposure to assess the sublethal effects of treatments on certain life-history traits. Results The predominant species in the study site was Anopheles gambiae sensu stricto (An. gambiae s.s.). Both Anopheles coluzzii and An. gambiae s.s. were resistant to pyrethroids (deltamethrin susceptibility was restored by piperonyl butoxide pre-exposure). In the experimental hut trials, the highest blood-feeding inhibition (5.56%) was recorded for the Royal Guard net, relative to the standard PermaNet 2.0 net (44.44% inhibition). The highest 72-h mortality rate (90.11%) was recorded for the Interceptor G2 net compared to the PermaNet 2.0 net (56.04%). After exposure, the risk of death of An. gambiae sensu lato (An. gambiae s.l.) was 6.5-fold higher with the Interceptor G2 net and 4.4-fold higher with the PermaNet 3.0 net compared to the respective untreated net. Lower mosquito mortality was recorded with an aged Interceptor G2 net compared to a new Interceptor G2 net. Oviposition rates were lower in mosquitoes collected from huts containing ITNs compared to those of untreated controls. None of the mosquitoes collected from huts equipped with Royal Guard nets laid any eggs. Conclusions The Royal Guard and Interceptor G2 nets showed a potential to significantly improve the control of malaria-transmitting vectors. However, the PermaNet 3.0 net remains effective in pyrethroid-resistant areas. Graphical Abstract

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Pyrethroid-treated bed nets impair blood feeding performance in insecticide resistant mosquitoes

Cited by 7 publications

References 52 publications

Community benefits of mass distribution of three types of dual-active-ingredient long-lasting insecticidal nets against malaria prevalence in Tanzania: evidence from a 3-year cluster-randomized controlled trial

Community benefits of mass distribution of three types of dual-active-ingredient long-lasting insecticidal nets against malaria prevalence in Tanzania: evidence from a 3-year cluster-randomized controlled trial

Video-tracked Anopheles arabiensis entry and exit behaviour at washed and damaged pyrethroid-treated bednets

Efficacy of Interceptor G2, Royal Guard and PermaNet 3.0 against pyrethroid-resistant Anopheles gambiae s.l. from Za-Kpota, southern Benin: an experimental hut trial

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