The insecticidal activity of essential oil constituents against pyrethroid-resistant Anopheles funestus (Diptera: Culicidae)

Thankhoe A Rants'o; Lizette L Koekemoer; Robyn L van Zyl

doi:10.1016/j.parint.2023.102749

The insecticidal activity of essential oil constituents against pyrethroid-resistant Anopheles funestus (Diptera: Culicidae)

Parasitol Int. 2023 Aug:95:102749. doi: 10.1016/j.parint.2023.102749. Epub 2023 Mar 9.

Authors

Thankhoe A Rants'o¹, Lizette L Koekemoer², Robyn L van Zyl³

Affiliations

¹ Pharmacology Division, Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; WITS Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. Electronic address: thankhoe.rantso@wits.ac.za.
² WITS Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.
³ Pharmacology Division, Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; WITS Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.

PMID: 36898498
DOI: 10.1016/j.parint.2023.102749

Abstract

Malaria vector control relies on the use of insecticides for indoor residual spraying and long-lasting bed nets. However, insecticide resistance to pyrethroids among others, has escalated. Anopheles funestus, one of the major African malaria vectors, has attained significant levels of resistance to pyrethroids. Overexpressed P450 monooxygenases have been previously identified in pyrethroid resistant An. funestus. The escalating resistance against conventional insecticides signals an urgent need for identification of novel insecticides. Essential oils have gained recognition as promising sources of alternative natural insecticides. This study investigated six essential oil constituents, farnesol, (-)-α-bisabolol, cis-nerolidol, trans-nerolidol, methyleugenol, santalol (α and β isomers) and essential oil of sandalwood, for the adulticidal effects against pyrethroid-resistant An. funestus strain. The susceptibility against these terpenoids were evaluated on both pyrethroid-susceptible and resistant An. funestus. Furthermore, the presence of overexpressed monooxygenases in resistant An. funestus was confirmed. Results showed that both the pyrethroid-susceptible and resistant An. funestus were susceptible to three EOCs; cis-nerolidol, trans-nerolidol and methyleugenol. On the other hand, the pyrethroid-resistant An. funestus survived exposure to both farnesol and (-)-α-bisabolol. This study however does not show any direct association of the overexpressed Anopheles monooxygenases and the efficacy of farnesol and (-)-α-bisabolol. The enhanced activity of these terpenoids against resistant An. funestus that has been pre-exposed to a synergist, piperonyl butoxide, suggests their potential effectiveness in combination with monooxygenase inhibitors. This study proposes that cis-nerolidol, trans-nerolidol and methyleugenol are potential agents for further investigation as novel bioinsecticides against pyrethroid-resistant An. funestus strain.

Keywords: Insecticides; Malaria; Monooxygenases; Synergy; Terpenoids.

MeSH terms

Animals
Anopheles*
Farnesol / pharmacology
Insecticides* / pharmacology
Malaria*
Mixed Function Oxygenases
Mosquito Control
Mosquito Vectors
Oils, Volatile* / pharmacology
Pyrethrins* / pharmacology

Substances

Insecticides
Pyrethrins
nerolidol
bisabolol
Oils, Volatile
methyleugenol
Farnesol
Mixed Function Oxygenases