Acaricide effect of native and exotic plants from the Brazilian savanna on Rhipicephalus microplus-resistant ticks with notes on the acaricide resistance of tick populations collected in southeast Brazil

Abstract

Rhipicephalus microplus is among the most important ectoparasites for livestock. The use of chemical acaricides has raised some concerns due to the selection of tick populations that are resistant to acaricides and environmental contamination. Therefore, plant extracts have been used as alternatives for the treatment of animals infested with ticks. In this study, R. microplus populations from seven different dairy farms were collected and assessed for their resistance to acaricides. Larvae of the most resistant population was used in assays to evaluate the acaricide effect of extracts from leaves or the latex of eight plant species commonly found in Brazilian dairy farms. The most active extracts were also tested against fully engorged females. Among seven tick populations, five and three showed resistance level ≥ III for cypermethrin or trichlorfon, respectively. The most resistant population was used in mortality assays with the plants Piptadenia viridiflora, Annona crassiflora, Caryocar brasiliense, Ximenia americana, Schinopsis brasilienses, Mangifera indica, Tithonia diversifolia, and Calotropis procera. C. procera was the most effective against larvae with mortalities of 62.9 and 44.9% at 100 mg/mL with the latex and aqueous extract, respectively. The ethanolic extracts of C. brasiliense, S. brasilienses, and X. americana also had acaricide effects higher or similar to cypermethrin. When fully engorged females were tested, the aqueous extract of C. procera showed a 96.8% efficiency. Four of the plants tested showed promising results, and further studies should be carried out for the development of tools to control R. microplus in cattle.