Efficacy of essential oils of Egletes viscosa and Lippia schaueriana on the reproductive biology of Rhipicephalus sanguineus sensu lato engorged females

Ticks are important vectors of many diseases that affect humans, domestic animals, and livestock, causing significant economic losses. On a global scale, the damages caused by these ectoparasites represent an economic burden of 20–30 billion per year (Lew-Tabor and Rodriguez Valle, 2016). Many factors must be considered in determining the global impact of ticks, mainly due to their feeding habits, which can cause tissue damage and anemia by blood loss, directly affecting cattle milk and meat production, in addition to creating conditions for secondary bacterial infections or myiasis on their hosts (Jongejan and Uilenberg, 2004).

The brown dog tick, Rhipicephalus sanguineus sensu lato (s. l.), represents a threat to public health in all stages of development as a vector of Ehrlichia canis (ehrlichiosis), Babesia canis (babesiosis) and Hapatozoon canis (hepatozoonosis), which cause diseases that affect a large number of dogs worldwide (Dantas-Torres, 2010; Dantas-Torres and Otranto, 2015). Furthermore, this parasite transmits several bacteria, such as Rickettsia spp., the causative agent of Rocky Mountain Spotted Fever in Europe (R. conorii) and USA (R. rickettsii) (Borges et al., 2007). In Brazil, R. sanguineus s.l. was reported to be infected with R. parkeri, another etiologic agent of Brazilian Spotted Fever (BSF) (Cunha et al., 2009; Moerbeck et al., 2016; Silva et al., 2017).

The use of chemical acaricides, mainly synthetic ones, is the most common and widely used strategy to control ticks. Despite their efficiency, synthetic acaricides cause significant environmental damage, contaminating soils and water streams (Camargo-Mathias, 2018). Furthermore, these chemicals can also affect non-target organisms, including animals and humans, since most of them present high levels of toxicity (Cunha et al., 2017).

The rate at which tick species can develop resistance to an acaricide has been a challenge, mainly for developing countries where the indiscriminate and inappropriate use of synthetic products is a common practice (Higa et al., 2015; Lew-Tabor and Rodriguez Valle, 2016). The search for new alternatives to control these ectoparasites has stimulated the studies with essential oils (EOs), since they contain an arsenal of secondary metabolites that are part of plant defense strategies (Castro et al., 2018) and have been proven effective to control pests (Anholeto et al., 2017; Nolan, 1985; Oliveira and Camargo-Mathias, 2018).

Egletes viscosa (L.) Less. (Asteraceae) is an endemic species to tropical America including the northeast of Brazil (Lorenzi and Mattos, 2008) and is popularly known as “macela” or “macela-da-terra” (Pereira et al., 2018). E. viscosa contains compounds with pharmacological properties, including insecticide and acaricide activity (Guimarães et al., 2011; Jamuna et al., 2015; Prats et al., 2006; Rao et al., 2003; Tripathi et al., 2011; Zhou et al., 2019).

Lippia schaueriana Mart. (Verbenaceae) is a Caatinga endemic species, mainly found in the states of Bahia and Pernambuco (Brazil), although it can also be found in other states of the northeast, more specifically in transitional vegetation zones (Lorenzi and Mattos, 2008; Souza et al., 2018). In the northeast of Brazil, this plant is popularly known as “alecrim-de-mocó” or “lipia-da-serra”. Although the literature does not present data on the acaricide effect of L. schaueriana, several studies have addressed the acaricide effect of Lippia plants against larvae, nymphs and adults of R. sanguineus s. l., Amblyomma cajennense, Dermacentor nitens (Gomes et al., 2012, 2014) and R. microplus (Costa-Júnior et al., 2016; Cruz et al., 2013; Lage et al., 2013; Peixoto et al., 2015).

Thus, the objective of the present study was to bring data regarding the acaricide effect of essential oils extracted from the leaves and flowers of two tropical American plant species, Egletes viscosa Less. (Asteraceae) and Lippia schaueriana Mart. (Verbenaceae) and study their effects on the reproductive biology of R. sanguineus s.l. engorged females.

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