The effects of pennyroyal oil and other natural insect repellants used in a rabbit experimental housing system

Abstract

Pennyroyal (Mentha pulegium, Lamiaceae family) has been extensively used in the past for its repellent activity against insects and mites, particularly in local dwellings. A recent study was conducted on the repellent activity of pennyroyal against mosquitoes. The aim of this project was to determine whether the essential oil of Mentha pulegium exhibited a repellent activity in a household amateur rabbitry. The oil was extracted from plant samples obtained locally, using the B.P. Steam distillation equipment and a semi-industrial brass distiller. A household amateur rabbitry was set up in a local garage and an insect trap was constructed. Seven rabbits were introduced in the setup and after acclimatization; insect repellency tests were conducted using pennyroyal oil, against citronella oil, basil oil, tea tree oil and two negative controls (no treatment). For each treatment or control, a week application was used. Daily records of temperature, humidity and insect/mites trapped were recorded. From this study, it was observed that there was no significant difference between the extraction of pennyroyal oil using the B.P. Method and the semi-industrial brass distiller. All essential oils tested exhibited a repellent activity against one or more insect and mite species. Citronella oil was repellent to seven species, followed by tea tree (six), then pennyroyal (four) and finally basil oil (three). The probable constituents that were mainly repellent in the different oils include methyl cinnamate and methyl eugenol in mainly basil oil, geraniol and citronella! mainly in citronella oil, pulegone mainly in pennyroyal oil, and terpinen-4-ol and y-terpinene in tea tree oil. A constituent that probably exhibited attraction to some species was limonene. It could be concluded that the oils tested exhibited a potential repellent activity in an animal setup, using natural products.