Effect of essential oils against acaricide-susceptible and acaricide-resistant Rhipicephalus ticks

Abstract

The indiscriminate use of acaricides is a problem worldwide and has increased the selection of acaricide-resistant tick populations. The goal of this study was to evaluate the acaricide effects of two essential oils (from Schinus molle and Bulnesia sarmientoi) using the larval immersion test on three Rhipicephalus tick species. Rhipicephalus evertsi, Rhipicephalus appendiculatus and Rhipicephalus pulchelus ticks collected in Kenya, without history of acaricide exposure, were tested, as well as individuals from two populations of Rhipicephalus microplus (with or without history of acaricide exposure), for comparison. The sample most resistant to the treatments was a population of R. microplus with previous acaricide exposure, whereas the least tolerant sample was a strain of the same species that never had contact with acaricides (Porto Alegre strain). Interestingly, the field tick samples without previous acaricide exposure responded to essential oils with a mortality profile resembling that observed in the acaricide-resistant R. microplus field population, and not the susceptible Porto Alegre strain. The essential oil of B. sarmientoi and its two components tested (guaiol and bulnesol) caused the highest mortality rates in the tested species and are potential molecules for future studies on control methods against these species.

Keywords: Acaricide; Bulnesia sarmientoi; Essential oil; Rhipicephalus spp; Schinus mole; Tick.

Fig. 1

Mean (+ SD; n = 3) mortality of larvae from acaricide-susceptible Rhipicephalus microplus (Porto Alegre strain) after exposure to essential oils and their main components. a Schinus molle essential oil, b α-phellandrene, c sabinene, d Bulnesia sarmientoi essential oil, e bulnesol, and f guaiol. Means capped with the same letter are not significantly different (Tukey test: p > 0.05)

Fig. 2

Mean (+ SD; n = 3) mortality of larvae from acaricide-resistant Rhipicephalus microplus field population after exposure to essential oils and their main components. a Schinus molle essential oil, b α-phellandrene, c sabinene, d Bulnesia sarmientoi essential oil, e bulnesol, and f guaiol. Means capped with the same letter are not significantly different (Tukey test: p > 0.05)

Fig. 3

Mean (+ SD; n = 3) mortality of larvae from Rhipicephalus evertsi African field population after exposure to essential oils and their main components. a Schinus molle essential oil, b α-phellandrene, c sabinene, d Bulnesia sarmientoi essential oil, e bulnesol, and f guaiol. Means capped with the same letter are not significantly different (Tukey test: p > 0.05)

Fig. 4

Mean (+ SD; n = 3) mortality of larvae from Rhipicephalus appendiculatus African field population after exposure to essential oils and their main components. a Schinus molle essential oil, b α-phellandrene, c sabinene, d Bulnesia sarmientoi essential oil, e bulnesol, and f guaiol. Means capped with the same letter are not significantly different (Tukey test: p > 0.05)

Fig. 5

Mean (+ SD; n = 3) mortality of larvae from Rhipicephalus pulchellus African field population after exposure to essential oils and their main components. a Schinus molle essential oil, b α-phellandrene, c sabinene, d Bulnesia sarmientoi essential oil, e bulnesol, and f guaiol. Means capped with the same letter are not significantly different (Tukey test: p > 0.05)

Fig. 6

Heat map of essential oil effects on Rhipicephalus spp. Data are presented as percentage mortality (0–100%) after treatment with essential oils or isolated compounds at concentrations from 0.01 to 10% in larval immersion tests of a laboratory maintained R. microplus strain; b R. microplus field population; c R. evertsi wild population; d R. appendiculatus wild population; and e R. pulchellus wild population. The map shows the drastic difference in xenobiotic resistance between samples with or without history of acaricide exposure, and the resistance in African ticks. Sm, Schinus molle oil; Ap, α-phellandrene; Sn, sabinene; Bs, Bulnesia sarminetoi oil; Bl, bulnesol; Gl, guaiol