Longitudinal evaluation of repellent activity of Ocimum gratissimum (Labiatae) volatile oil against Simulium damnosum

Abstract

To determine the repellent activity of Ocimum gratissimum volatile oil against Simulium damnosum (blackflies), a 12 month (January-December 2003) field study was conducted in three onchocerciasis endemic communities (Idomido, Ohio camp, and Ikot Adaha) in Ini Local Government Area of Akwa Ibom State, Nigeria. The result revealed that topical application of 20% (v/v) concentration of the oil with liquid paraffin as a base, reduced the biting rate of S. damnosum by 90.2, 81.6, and 79.7%, in Idomido, Obiocamp, and Ikot Adaha respectively. The oil gave protection against the bite of S. damnosum for at leant 3 h. A total of 710 adult.i S. damnosum were caught by individuals treated with Ocimum oil, an against 4296 caught by the control group. When the flies caught by the treated individuala were dissected none of them was infected with microfilariae of Onchocerca volvulus. Humanvector contact and onchocerciasis transmission could be reduced by the topical application of the volatile oil during the peak biting periods of the vector.