Seasonal variations in the biting densities of Simulium damnosum complex (Diptera: Simuliidae) in Enugu state, Nigeria: implications for farmers

Abstract

Seasonal variations in the biting densities of Simulium damnosum complex were studied in Uzo-Uwani Local Government Area of Enugu State, Nigeria, with the objectives of discovering the season with the highest biting densities and relating the seasonal biting densities with the farming seasons of the people. The study was carried out in different seasons of the year between April, 1999 and March, 2000. Two human baits were used to catch biting flies between 6.00a.m. and 7.00p.m. on each fly-catching day. The average numbers of flies caught per man per hour and per man per day were recorded. The results showed variations between the different seasons studied. The highest average biting densities of 30 flies/man/day were recorded during the dry season with harmattan but biting activities of the flies were concentrated in the evenings. The second highest average biting densities of about 25 flies/man/day were recorded during the early rainy season and biting activities were spread throughout the day with morning and evening peaks. Low average biting densities of about 4 flies/man/day and about 11 flies/man/day were recorded during the dry season without harmattan and late rainy season respectively. The probability of finding biting flies at any given hour was highest (0.91) during the early rainy season. This very high probability of man-fly contact coupled with the most intense farming activities (clearing and cultivation) within this season makes it very dangerous to farmers. It is recommended that the farmers take such precautions as covering themselves better and using repellents to prevent man-fly contact during farm work..

Keywords: Seasonal variations, biting densities, Simulium damnosum, onchocerciasis

Agro-Science Vol. 4 (1) 2005: pp. 10-13