Chemical composition and acaricidal activity of Eucalyptus globulus essential oil against the vector of tropical bovine piroplasmosis, Rhipicephalus (Boophilus) annulatus.

Ticks are of great economic importance to humans and animals due to their role in disease transmission. The application of synthetic, chemical acaricides on the animal and/or the environment (the most used tick control method globally) has led to the selection of tick populations that are resistant. Their adverse effects on ecology and human and animal health cannot be overemphasised. As a result, the search for alternatives that are natural and can overcome these adverse effects are strongly indicated. Using gas chromatography-mass spectrometry (GC-MS) and adult immersion test (AIT), this study evaluated the chemical composition and acaricidal activity, respectively, of Eucalyptus globulus essential oil (EO) on Rhipicephalus (Boophilus) annulatus ticks. This is a major tick species implicated for the transmission of bovine piroplasmosis in Nigeria. The acaricidal activity was evaluated using different concentrations (0.625, 1.25, 2.5, 5 and 10%) of E. globulus EO. Amitraz (1 and 2%) and cypermethrin (2%) served as the positive control and 2% dimethylsulfoxide in distilled water was the negative control. Three replicates of 10 engorged female ticks each were immersed in the test samples for 2 min and the experiment was done twice. The GC-MS analysis identified the major constituents of E. globulus EO as eucalyptol (1,8-cineole) (78%), menthol (20%) and menthone (3%). Eucalyptus globulus EO caused 97% acaricidal mortality at 10% concentration. The lower concentrations reduced tick fecundity up to 90% in a dose-dependent manner. This study provides support for plant EOs as alternative tick control strategy for humans and animals.