Exposure of Rhipicephalus sanguineus sensu lato Latreille, 1806 (Acari: Ixodidae) to hexane extract of Acmella oleracea (Jambu): semi-engorged and engorged ticks.

The present study analyzed the efficacy of hexane extract of Acmella oleracea against Rhipicephalus sanguineus sensu lato. After exposure of R. sanguineus s. l. female ticks to 14 different concentrations of the hexane extract of A. oleracea, the LC ₅₀ was established as 18.135 mg/mL (limits: 16.251-22.675). The effects of the extract were more significant in the ovary of the semi-engorged females, that presented damages in most oocytes. Since such changes would not be repaired, the oocytes could not advance to further stages of development (I-V), thereby causing the inhibition of ovary development, interruption of vitellogenesis, oocyte death and, consequently, infertility. The semi-engorged females also presented extensive damages in the midgut cells, which would prevent (totally or partially) these cells from functioning properly (blood intake and release of nutrients), impairing the ectoparasite nutrition and the viability of the individual. Thus, the hexane extract of A. oleracea can be considered as a promising alternative to chemical control of pests of medical and veterinary importance, due to its efficient acaricidal activity and lesser environmental impact, when used against female ticks in the middle feeding stage.
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