Empirical and theoretical investigation into the potential impacts of insecticide resistance on the effectiveness of insecticide‐treated bed nets

Glunt, Katey D.; Coetzee, Maureen; Huijben, Silvie; Koffi, Alphonsine A.; Lynch, Penelope A.; N’Guessan, Raphaël; Oumbouke, Welbeck A.; Sternberg, Eleanore D.; Thomas, Matthew B.

doi:10.1111/eva.12574

Cited by 54 publications

(66 citation statements)

References 46 publications

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“…Females that were exposed to deltamethrin fed less than females that were not exposed. Our findings were consistent with Glunt et al, [26] and contrary to what was observed by Tchakounte et al, [27] who showed that exposure of mosquitoes to PermaNet 2.0 deltamethrintreated bednet presented no effect of on their blood feeding ability. From an epidemiological point of view, our findings can be translated into a reduction in transmission as the drop in the rate of mosquito bites also means less risk of infection with plasmodium.…”

Section: Discussionsupporting

confidence: 93%

Impact of sublethal pyrethroid exposure on resistant Anopheles gambiae mosquitoes’ fitness

Kropf

Fodjo

Zoh

et al. 2020

Preprint

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Background : There is increasing evidence of insecticide resistance spreading among wild mosquito populations, which is widely believed to compromise vector control once it reaches a threshold that enables mosquitoes to survive exposure to long lasting treated bed-net (LLIN) or indoor residual spraying (IRS). However, very little is known about the long-term impact of insecticide resistance on malaria transmission, which makes the consequence of insecticide resistance spreading difficult to predict. Methods: To gain more clarity, we have assessed five life-history traits of a resistant Anopheles gambiae laboratory strain that was repeatedly exposed to a LLIN and compared with individuals issued from the same strain but exposed to an untreated bed-net. Results: The non-parametric Kruskal-Wallis test did not show any significant impact of gonotrophic cycle on the five traits. However, the Kolmogorov-Smirnov non-parametric test revealed a significant (i) drop in blood feeding mean rates (D = 0.800; P< 0.0001), (ii) increase in 24-hours post-exposure (D = 0.600; P< 0.001) and (iii) end of gonotrophic cycle mortality (D = 0.611; P <0.006), and (iv) drop in egg laying rate (D = 0.730, P< 0.0001) when mosquitoes were exposed. Surprisingly, there was rather an upward trend in the number of L3 larvae/female mosquito for the exposed group comparing to the unexposed one, although the difference was not significant (D = 0.417, P> 0.05). Conclusion: Our study shows that in a context of widespread of resistance to insecticides, current pyrethroid-based vector control tools can still confer protection against malaria.

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Section: Discussionsupporting

confidence: 93%

Impact of sublethal pyrethroid exposure on resistant Anopheles gambiae mosquitoes’ fitness

Kropf

Fodjo

Zoh

et al. 2020

Preprint

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“…Studies have shown that deltamethrin-treated nets reduced blood-feeding of Anopheles, suggesting that this inhibition could be due to contact irritancy [37,40]. In a similar study to ours, Glunt et al [11] also found blood-feeding inhibition in SENN-DDT (1×), FUMOZ (5×), and FUMOZ-R (10×) when mosquitoes were given access to a host after LLIN exposure (and not during exposure). Surprisingly, our results show a much higher feeding compliance in FUMOZ-R on the LLIN than on the untreated net in the tent assay, for which we do not have a good explanation.…”

Section: Discussionsupporting

confidence: 81%

“…Other studies, however, have found that LLINs are still more effective in preventing both clinical and subclinical malaria infections than untreated nets in areas with high pyrethroid resistance [5][6][7][8], including a 4-year WHO-coordinated 5-country cohort study that found no association between pyrethroid resistance and malaria incidence or prevalence in the field [9]. While observational studies need to be treated with caution as they cannot control for various factors and tend to only assess personal protection (a modeling analysis suggests that there could be loss of community protection even if levels of personal protection from LLINs remains high [10]), there are clearly complexities in interpreting the epidemiological consequences of resistance [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…First, LLINs provide a physical barrier that can reduce biting rate regardless of insecticidal activity. Secondly, there may be sub-lethal effects to insecticide exposure, so that when a resistant mosquito contacts insecticide, it might experience a decrease in its ability to blood-feed and host-seek [11], or even incubate the parasite [13,14]. Thirdly, alleles that confer resistance in mosquitoes might also reduce vector competence in the absence of insecticide exposure [15].…”

Section: Introductionmentioning

confidence: 99%

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Use of alternative bioassays to explore the impact of pyrethroid resistance on LLIN efficacy

et al. 2020

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Background: There is substantial concern that the spread of insecticide resistance will render long-lasting insecticide-treated nets (LLINs) ineffective. However, there is limited evidence supporting a clear association between insecticide resistance and malaria incidence or prevalence in the field. We suggest that one reason for this disconnect is that the standard WHO assays used in surveillance to classify mosquito populations as resistant are not designed to determine how resistance might impact LLIN efficacy. The standard assays expose young, unfed female mosquitoes to a diagnostic insecticide dose in a single, forced exposure, whereas in the field, mosquitoes vary in their age, blood-feeding status, and the frequency or intensity of LLIN exposure. These more realistic conditions could ultimately impact the capacity of "resistant" mosquitoes to transmit malaria. Methods: Here, we test this hypothesis using two different assays that allow female mosquitoes to contact a LLIN as they host-seek and blood-feed. We quantified mortality after both single and multiple exposures, using seven different strains of Anopheles ranging in pyrethroid resistance intensity. Results: We found that strains classified as 1×-resistant to the pyrethroid insecticide deltamethrin in the standard WHO assay exhibited > 90% mortality over 24 h following more realistic LLIN contact. Mosquitoes that were able to blood-feed had increased survival compared to their unfed counterparts, but none of the 1×-resistant strains survived for 12 days post-exposure (the typical period for malaria parasite development within the mosquito). Mosquitoes that were 5×-and 10×-resistant (i.e. moderate or high intensity resistance based on the WHO assays) survived a single LLIN exposure well. However, only about 2-3% of these mosquitoes survived multiple exposures over the course of 12 days and successfully blood-fed during the last exposure. Conclusions: These results suggest that the standard assays provide limited insight into how resistance might impact LLIN efficacy. In our laboratory setting, there appears little functional consequence of 1×-resistance and even mosquitoes with moderate (5×) or high (10×) intensity resistance can suffer substantial reduction in transmission potential. Monitoring efforts should focus on better characterizing intensity of resistance to inform resistance management strategies and prioritize deployment of next generation vector control products.

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“…Glunt et al. () further discuss the challenges of insecticide resistance in the context of malaria, with a specific focus on pyrethroids impregnated long‐lasting insecticidal bed nets (LLINs) and their efficacy in preventing malaria. About 1 billion LLINs, a major vector control tool, have been distributed in Africa in the last 10 years.…”

Section: Themes Of the Special Issuementioning

confidence: 99%

Evolutionary perspectives on human infectious diseases: Challenges, advances, and promises

Echaubard

Rudge

Lefèvre

2018

Evolutionary Applications

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Empirical and theoretical investigation into the potential impacts of insecticide resistance on the effectiveness of insecticide‐treated bed nets

Cited by 54 publications

References 46 publications

Impact of sublethal pyrethroid exposure on resistant Anopheles gambiae mosquitoes’ fitness

Impact of sublethal pyrethroid exposure on resistant Anopheles gambiae mosquitoes’ fitness

Use of alternative bioassays to explore the impact of pyrethroid resistance on LLIN efficacy

Evolutionary perspectives on human infectious diseases: Challenges, advances, and promises

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