The oregano, Origanum onites L., essential oil (EO) was tested in laboratory behavioural bioassays for repellent activity against Amblyomma americanum (L.) and Aedes aegypti (L.). The O. onites EO was characterised using GC-FID and GC-MS. Carvacrol (75.70%), linalool (9.0%), p-cymene (4.33%) and thymol (1.9%) were the most abundant compounds. At a concentration of 0.413 mg oil/cm2 of filter paper, O. onites EO repelled 100% of the ticks tested and at 0.103 mg oil/cm2 of filter paper, 66.7% of the ticks were repelled. At 0.075 mg oil/cm2 filter paper, thymol repelled 66.7% of the ticks compared to 28.7% by carvacrol at that same concentration. Against Ae. aegypti, O. onites EO was repellent at the minimum effective dosage (MED) of 0.011 (±0.00) mg/cm2 in the cloth patch assay compared to the reference control, N,N-dimethyl-3-methylbenzamide (DEET) with a MED = 0.007 ± (0.003) mg/cm2.
Keywords: (−)-linalool; Aedes aegypti; Amblyomma americanum; Origanum onites; carvacrol; natural repellency; terpinolene; thymol; α-humulene.