Evaluation of the toxicity and repellence of an organic fatty acids mixture (C8910) against insecticide susceptible and resistant strains of the major malaria vector Anopheles funestus Giles (Diptera: Culicidae).

Michael Samuel,Basil D Brooke,Maureen Coetzee,Oliver R Wood,Shüné V Oliver

doi:10.1186/s13071-015-0930-2

Michael Samuel, Basil D Brooke + Show 3 more

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https://doi.org/10.1186/s13071-015-0930-2

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Journal: Parasites & vectors	Publication Date: Jun 12, 2015
Citations: 37	License type: CC BY 4.0

Affiliation: University of the Witwatersrand

Abstract

BackgroundMalaria vector control relies principally on the use of insecticides, especially pyrethroids. Because of the increasing occurrence of insecticide resistance in target vector populations, the development of new insecticides, particularly those with novel modes of action, is particularly important, especially in terms of managing insecticide resistance. The C8910 formulation is a patented mixture of compounds comprising straight-chain octanoic, nonanoic and decanoic saturated fatty acids. This compound has demonstrated toxic and repellent effects against several arthropod species. The aims of this study were to measure the insecticidal effects of C8910 against an insecticide susceptible (FANG) and a pyrethroid resistant (FUMOZ-R) laboratory strain of An. funestus as well as against wild-caught An. funestus material from Zambia (ZamF), and to investigate the repellent effects of two formulations of C8910 against these strains.MethodsToxicity against adult females was assessed using a range of concentrations based on the CDC bottle bioassay method and repellence of three different C8910 formulations was assessed using standard choice-chamber bioassays.ResultsC8910 proved equally toxic to adult females of the FUMOZ-R and FANG laboratory strains, as well as to adult females of the wild-caught (ZamF) sample. None of the C8910 formulations tested gave any conclusive indication of repellence against any of the strains.ConclusionC8910 is equally effective as an adulticide against pyrethroid resistant and insecticide susceptible An. funestus. However, the formulations tested did not show any consistent repellence against laboratory reared and wild-caught female samples of this species. Nevertheless, C8910 shows potential as an adulticide that can be used for malaria vector control, particularly in those instances where insecticide resistance management is required.

Highlights

Malaria vector control relies principally on the use of insecticides, especially pyrethroids
The aims of this study were to measure the insecticidal effects of C8910 against insecticide susceptible and pyrethroid resistant laboratory strains of An. funestus as well as against wild-caught An. funestus from Zambia, and to investigate the repellent effects of two formulations of C8910 against these strains
A Tukey HSD post-hoc test of the ZamF 50-250 μg/ml a.i dose range shows that the significant trend (F = 3.4, p = 0.04) indicated by one-way Analysis of variance (ANOVA) does not reflect a significant difference in mean mortalities

Summary

Introduction

Malaria vector control relies principally on the use of insecticides, especially pyrethroids. Anopheles funestus Giles is a primary malaria vector species in the Afrotropical region [2, 3] and is the nominal member of the Funestus Subgroup which comprises four species: An. funestus, An. parensis, An. vaneedeni and An. confusus. These are almost morphologically indistinguishable at all life stages [3, 4]. Anopheles funestus females are highly anthropophilic and endophilic, and often take multiple blood meals These characteristics combined with a relatively high longevity make An. funestus populations especially efficient at malaria transmission, and often show higher Plasmodium falciparum sporozoite infection rates than other vector species [5]

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