Chemicals, Climate, and Control: Increasing the Effectiveness of Malaria Vector Control Tools by Considering Relevant Temperatures

Glunt, Katey D.; Blanford, Simon; Paaijmans, Krijn P.

doi:10.1371/journal.ppat.1003602

Cited by 41 publications

(35 citation statements)

References 36 publications

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“… Susceptibility tests: Insecticide susceptibility as determined with standard bioassays may not reflect susceptibility under actual field conditions as such tests are performed with young (2‐ to 5‐day‐old) female mosquitoes following single, limited‐time exposure to an insecticide under constant insectary conditions. As a result, the effect of natural mosquito traits such as sex, age, blood‐feeding status and circadian rhythm (Kulma, Saddler, & Koella, ; Oliver & Brooke, ) but also climatic variables (Glunt, Blanford, & Paaijmans, ) on the toxicity of insecticides is not captured, neither are sublethal effects on blood‐feeding and host‐seeking factors (Glunt et al., unpublished), infection with entomopathogens such as Plasmodium (Alout et al., ), or delayed mortality (Viana, Hughes, Matthiopoulos, Ranson, & Ferguson, ). Vector species: Resistance is typically characterized for a few major malaria vectors in a given area, but there may be several other malaria vectors present. Although we have always assumed that there are roughly 30‐40 malaria vectors worldwide, recently molecular tools show us we may be dealing with a larger diversity of vector species as well as population diversity within one species (Lobo et al., ). Behavioural changes: Apart from the conventional resistance mechanism (target site, metabolic or cuticular resistance), vectors that can avoid contact with insecticides have a clear selective advantage.…”

Section: Antimalarial Interventions and Their Evolutionary Consequencesmentioning

confidence: 99%

Putting evolution in elimination: Winning our ongoing battle with evolving malaria mosquitoes and parasites

Huijben

Paaijmans

2017

Evolutionary Applications

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Since 2000, the world has made significant progress in reducing malaria morbidity and mortality, and several countries in Africa, South America and South‐East Asia are working hard to eliminate the disease. These elimination efforts continue to rely heavily on antimalarial drugs and insecticide‐based interventions, which remain the cornerstones of malaria treatment and prevention. However, resistance has emerged against nearly every antimalarial drug and insecticide that is available. In this review we discuss the evolutionary consequences of the way we currently implement antimalarial interventions, which is leading to resistance and may ultimately lead to control failure, but also how evolutionary principles can be applied to extend the lifespan of current and novel interventions. A greater understanding of the general evolutionary principles that are at the core of emerging resistance is urgently needed if we are to develop improved resistance management strategies with the ultimate goal to achieve a malaria‐free world.

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Section: Antimalarial Interventions and Their Evolutionary Consequencesmentioning

confidence: 99%

Putting evolution in elimination: Winning our ongoing battle with evolving malaria mosquitoes and parasites

Huijben

Paaijmans

2017

Evolutionary Applications

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“…The efficacy of a chemical against its target is also a function of the formulation, the biology of the insect, and the environment in which these interact [ 7 ]. Thus, it is difficult to predict how an insecticide susceptibility test in a laboratory or insectary, where insecticide dose, mosquito physiological status (e.g., age, blood feeding, larval nutrition) and climate are controlled [ 8 ], translates to the efficacy of an insecticide in the field [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

The impact of temperature on insecticide toxicity against the malaria vectors Anopheles arabiensis and Anopheles funestus

Glunt

Oliver

Hunt

et al. 2018

Malar J

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BackgroundIt is anticipated that malaria elimination efforts in Africa will be hampered by increasing resistance to the limited arsenal of insecticides approved for use in public health. However, insecticide susceptibility status of vector populations evaluated under standard insectary test conditions can give a false picture of the threat, as the thermal environment in which the insect and insecticide interact plays a significant role in insecticide toxicity.MethodsThe effect of temperature on the expression of the standard WHO insecticide resistance phenotype was examined using Anopheles arabiensis and Anopheles funestus strains: a susceptible strain and the derived resistant strain, selected in the laboratory for resistance to DDT or pyrethroids. The susceptibility of mosquitoes to the pyrethroid deltamethrin or the carbamate bendiocarb was assessed at 18, 25 or 30 °C. The ability of the pyrethroid synergist piperonyl-butoxide (PBO) to restore pyrethroid susceptibility was also assessed at these temperatures.ResultsTemperature impacted the toxicity of deltamethrin and bendiocarb. Although the resistant An. funestus strain was uniformly resistant to deltamethrin across temperatures, increasing temperature increased the resistance of the susceptible An. arabiensis strain. Against susceptible An. funestus and resistant An. arabiensis females, deltamethrin exposure at temperatures both lower and higher than standard insectary conditions increased mortality. PBO exposure completely restored deltamethrin susceptibility at all temperatures. Bendiocarb displayed a consistently positive temperature coefficient against both susceptible and resistant An. funestus strains, with survival increasing as temperature increased.ConclusionsEnvironmental temperature has a marked effect on the efficacy of insecticides used in public health against important African malaria vectors. Caution must be exercised when drawing conclusions about a chemical’s efficacy from laboratory assays performed at only one temperature, as phenotypic resistance can vary significantly even over a temperature range that could be experienced by mosquitoes in the field during a single day. Similarly, it might be inappropriate to assume equal efficacy of a control tool over a geographic area where local conditions vary drastically. Additional studies into the effects of temperature on the efficacy of insecticide-based interventions under field conditions are warranted.Electronic supplementary materialThe online version of this article (10.1186/s12936-018-2250-4) contains supplementary material, which is available to authorized users.

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“…This temperature-toxicity relationship can be determined by calculating the temperature coefficient of an insecticide. An insecticide with a positive temperature coefficient becomes more toxic with the increase in temperature, whereas, those with a negative temperature coefficient become more toxic at lower temperatures [17]. Pyrethroid and organophosphate insecticide classes, for example, usually have a negative and positive temperature coefficient, respectively [18].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Temperature on the Toxicity of Insecticides against Musca domestica L.: Implications for the Effective Management of Diarrhea

Khan

Akram

2014

PLoS ONE

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BackgroundDiarrhea is an important cause of childhood mortality in developing countries like Pakistan because of unhygienic conditions, lack of awareness, and unwise use of preventive measures. Mechanical transmission of diarrheal pathogens by house flies, Musca domestica, is believed as the most effective route of diarrhea transmission. Although the use of insecticides as a preventive measure is common worldwide for the management of house flies, success of the measure could be compromised by the prevailing environmental temperature since it significantly affects toxicity of insecticides and thus their efficacy. Peaks of the house fly density and diarrheal cases are usually coincided and season specific, yet little is known about the season specific use of insecticides.Methodology/Principal FindingsTo determine the temperature-toxicity relationship in house flies, the effect of post-bioassays temperature (range, 20–34°C) on the toxicity of seven insecticides from organophosphate (chlorpyrifos, profenofos), pyrethroid (cypermethrin, deltamethrin) and new chemical (emamectin benzoate, fipronil, spinosad) classes was evaluated by using a feeding bioassay method. From 20–34°C, the toxicities of chlorpyrifos, profenofos, emamectin and fipronil increased 2.10, 2.93, 2.40 and 3.82 fold (i.e. positive temperature coefficient), respectively. Whereas, the toxicities of cypermethrin, deltamethrin and spinosad decreased 2.21, 2.42 and 3.16 fold (i.e. negative temperature coefficient), respectively.Conclusion/SignificanceThese findings suggest that for the reduction in diarrheal cases, house flies should be controlled with insecticides according to the prevailing environmental temperature. Insecticides with a positive temperature coefficient may serve as potential candidates in controlling house flies and diarrhea epidemics in hot season and vice versa.

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Chemicals, Climate, and Control: Increasing the Effectiveness of Malaria Vector Control Tools by Considering Relevant Temperatures

Cited by 41 publications

References 36 publications

Putting evolution in elimination: Winning our ongoing battle with evolving malaria mosquitoes and parasites

Putting evolution in elimination: Winning our ongoing battle with evolving malaria mosquitoes and parasites

The impact of temperature on insecticide toxicity against the malaria vectors Anopheles arabiensis and Anopheles funestus

The Effect of Temperature on the Toxicity of Insecticides against Musca domestica L.: Implications for the Effective Management of Diarrhea

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