Abstract
The continuous and indiscriminate use of insecticides has been responsible for the emergence of insecticide resistant vector insect populations, especially in Aedes aegypti. Thus, it is urgent to find natural insecticide compounds with novel mode of action for vector control. The goal of this study was to investigate the larvicidal activity of essential oils (EOs) from Piper species against A. aegypti characterized as resistant and susceptible strains to pyrethroids. The EOs from leaves of 10 Piper species were submitted to the evaluation of larvicidal activity in populations of A. aegypti in agreement with the (World Health Organization, 2005) guidelines. The resistance of the strains characterized by determining the lethal concentrations (LCs) with the insecticide deltamethrin (positive control). The major compounds of the EOs from Piper species was identified by GC-MS. The EOs from Piper aduncum, P. marginatum, P. gaudichaudianum, P. crassinervium, and P. arboreum showed activity of up to 90% lethality at 100 ppm (concentration for screening). The activities of the EOs from these 6 species showed similar LCs in both susceptible strain (Rockefeller) and resistant strains (Pampulha and Venda Nova) to pyrethroids. The major compounds identified in the most active EO were available commercially and included β-Asarone, (E)-Anethole, (E)-β-Caryophyllene, γ-Terpinene, p-Cymene, Limonene, α-Pinene, and β-Pinene. Dillapiole was purified by from EO of P. aduncum. The phenylpropanoids [Dillapiole, (E)-Anethole and β-Asarone] and monoterpenes (γ-Terpinene, p-Cymene, Limonene, α-Pinene, and β-Pinene) showed larvicidal activity with mortality between 90 and 100% and could account for the toxicity of these EOs, but the sesquiterpene (E)-β-Caryophyllene, an abundant component in the EOs of P. hemmendorffii and P. crassinervium, did not show activity on the three populations of A. aegypti larvae at a concentration of 100 ppm. These results indicate that Piper's EOs should be further evaluated as a potential larvicide, against strains resistant to currently used pesticides, and the identification of phenylpropanoids and monoterpenes as the active compounds open the possibility to study their mechanism of action.
Highlights
Aedes aegypti (Linnaeus, 1762) (Mattingly et al, 1962) is a mosquito species known to transmit arboviruses such as dengue, chikungunya, and zika virus worldwide
Based on the bioassays with Deltamethrin, the strains of Pampulha and Venda Nova were shown to be resistant to this insecticide, with the population of Pampulha (RR95 = 26.073) being more resistant than the population of Venda Nova (RR95 = 20.512)
The resistance observed in these populations of A. aegypti for Deltamethrin is expected for pyrethroids in general, because of the similarity of the mode of action
Summary
Aedes aegypti (Linnaeus, 1762) (Mattingly et al, 1962) is a mosquito species known to transmit arboviruses such as dengue, chikungunya, and zika virus worldwide. It is a diurnal mosquito extremely adapted to urban and domestic environments (Macielde-Freitas et al, 2012). The control of A. aegypti populations still represents the best line of defense This strategy has focused on controlling the mosquito’s population by means of using insecticides such as the larvicide Pyriproxyfen (Juvenil Hormone Analog– JHA), the adulticides malathion (organophosphate) and Cielo R , an insecticide containing imidacloprid (neonicotinoid) and paletrine (pyrethroid) (Valle et al, 2019). In the last decades, the indiscriminate use of synthetic insecticides (for example, domestic use of pyrethroid insecticides available in the retail market, especially in epidemic periods), together with the lack of coordinated programs in multi-endemic areas, have led to the emergence of populations of A. aegypti resistant to different insecticides used (Maciel-de-Freitas et al, 2012; Macoris et al, 2018)
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