Anopheles gambiae populations from Burkina Faso show minimal delayed mortality after exposure to insecticide-treated nets

Hughes, Angela; Lissenden, Natalie; Viana, Mafalda; Toé, Hyacinthe K.; Ranson, Hilary

doi:10.1186/s13071-019-3872-2

Cited by 47 publications

(49 citation statements)

References 33 publications

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“…In our setting, the longevity was expressed by the mortality both at 24 hours post exposure, and at the end of the gonotrophic cycle. These two mortalities were affected by exposure to LLIN at each gonotrophic cycle contrary to observation made in Burjina Faso where following single and multiple exposures to a PermaNet 2.0 LLIN only one of the four mosquito populations tested showed evidence of delayed mortality [38].in our study, it increases by twice between the first and fourth gonotrophic cycles in unexposed mosquitoes, while it tripled over the same interval in the exposed group. By the end of gonotrophic cycle 4, mosquitoes were aged 25 to 28 days.…”

Section: Discussioncontrasting

confidence: 99%

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: Discussioncontrasting

confidence: 99%

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

Kropf

Fodjo

Zoh

et al. 2020

Preprint

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“…With the exception of chlorfenapyr, which is known to be a slow-acting insecticide, we did not detect any delayed mortality effects for 72 hours following insecticidal exposure; the format and dose used for clothianidin testing (another slow-acting insecticide [45]) was instead intended to measure acute toxicity within a minute exposure period. Previous mathematical models using resistant mosquito colonies have suggested that sub-lethal insecticide treatment may still reduce vector lifespan and inhibit blood-feeding and host-seeking behaviours, thereby interrupting malaria transmission [46,47]. Our observations are more compatible with reports from Burkina Faso where different exposure regimens of wild, resistant An.…”

Section: Malaria Prevalencesupporting

confidence: 89%

“…populations to deltamethrin LLINs did not induce any delayed mortality [47]. To date there is a paucity of data regarding the interactions between insecticide resistance and Plasmodium development [48].…”

Section: Malaria Prevalencementioning

confidence: 95%

Reduced long-lasting insecticidal net efficacy and pyrethroid insecticide resistance are associated with over-expression ofCYP6P4, CYP6P3andCYP6Z1in populations ofAnopheles coluzziifrom South-East Côte d’Ivoire

Meiwald

Clark

Kristan

et al. 2020

Preprint

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BackgroundResistance to major public health insecticides in Côte d’Ivoire has intensified and now threatens the long-term effectiveness of malaria vector control interventions.MethodsThis study evaluated the bioefficacy of conventional and next-generation long-lasting insecticidal nets (LLINs), determined resistance profiles, and characterized molecular and metabolic mechanisms in wild Anopheles coluzzii from South-East Côte d’Ivoire in 2019.ResultsPhenotypic resistance was intense: more than 25% of mosquitoes survived exposure to ten times the doses of pyrethroids required to kill susceptible populations. Similarly, 24-hour mortality to deltamethrin-only LLINs was very low and not significantly different to an untreated net. Sub-lethal pyrethroid exposure did not induce significant delayed vector mortality 72 hours later. In contrast, LLINs containing the synergist piperonyl butoxide (PBO), or new insecticides, clothianidin and chlorfenapyr, were highly toxic to An. coluzzii. Pyrethroid-susceptible An. coluzzii were significantly more likely to be infected with malaria, compared to those that survived insecticidal exposure. Pyrethroid resistance was associated with significant over-expression of CYP6P4, CPY6Z1 and CYP6P3.ConclusionsStudy findings raise concerns regarding the operational failure of standard LLINs and support the urgent deployment of vector control interventions incorporating PBO, chlorfenapyr or clothianidin in areas of high resistance intensity in Côte d’Ivoire.

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“…Births can only occur into generation i = 0 and vectors are assumed to survive up to a maximum of 10 gonotrophic cycles [42]. Using this model it is possible to calculate the parity of the population.…”

Section: Age Structurementioning

confidence: 99%

A novel age-structured mosquito model for assessing the mechanisms behind vector control success

Davis¹,

Hollingsworth

Keeling

2020

Preprint

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Background: Vector control is a vital tool utilised by malaria control and elimination programmes worldwide, and as such it is important that we can accurately quantify the expected public health impact of a range of vector control methods. There are very few previous models that consider vector control induced changes in the age-structure of the vector population and the resulting impact this will have on transmission.Methods: The steady-state solution of a novel age-structured deterministic compartmental model describing the mosquito gonotrophic cycle is analytically derived, with the age of each mosquito measured in the number of gonotrophic cycles (or successful blood meals) completed. From this model we derive analytical expressions for key transmission measures, such as the effective reproductive ratio under control, Rc, and investigate the impact of combinations of commonly used vector control methods on the age-structure of the vector population.Results: Our model output is an explicit solution that can be used to directly quantify key transmission statistics and investigate the age-structured impact of vector control. Application of this model confirms current knowledge thatadult-acting interventions, such as IRS or LLINs, can be highly effective at reducing transmission, due to the dual effects of repelling and killing mosquitoes. However, we demonstrate how larval measures can be implemented in addition to adult-acting measures to reduce Rc and mitigate the impact of waning insecticidal efficacy. We also find that mid-ranges of LLIN coverage see the largest effect of reduced net integrity on transmission.Conclusions: Whilst well-maintain adult-acting vector control measures are substantially more effective than larval-based interventions, incorporating larval control in existing LLIN or IRS programmes could substantially reduce transmission. This would most benefit areas with low coverage or poor maintenance of interventions.

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Anopheles gambiae populations from Burkina Faso show minimal delayed mortality after exposure to insecticide-treated nets

Cited by 47 publications

References 33 publications

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

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

Reduced long-lasting insecticidal net efficacy and pyrethroid insecticide resistance are associated with over-expression ofCYP6P4, CYP6P3andCYP6Z1in populations ofAnopheles coluzziifrom South-East Côte d’Ivoire

A novel age-structured mosquito model for assessing the mechanisms behind vector control success

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