Morphotaxonomic Studies and Abundance of Simulium damnosumTheobald (Diptera: Simuliidae) Complex in Two Local Government Areas of Ogun State

Abstract

The sibling species composition of Simulium damnosum sensulato and abundance of these sibling species in two communities (Opeji and Imala-Odo) of Ogun State south-western Nigeria was carried out in the wet months (May to October). Morphological identification of black flies using standard protocol was done from 07:00hr-18:00hr twice every two weeks. Climatic data like temperature, rainfall and relative humidity were documented for each month. A total of 1543 flies were dissected, 1228(79.6%) in Opeji and 315(20.4%) in Imala-Odo with a statistical significance (p<0.05). The result revealed an allopatric existence of forest dwelling flies. All the flies identified had dark fore coxa but there was variation in the colours of their wing tuft where wing tuft grade 05 was predominant and no fly had wing tuft grade 01 and there was significant difference (p<0.05) in the wing tuft colours observed among the flies. In Opeji, 477(38.8%) flies were parous while 155(49.2%) parous flies were recorded in Imala-Odo. However, no black fly was infected with the larva of Onchocerca volvulus. Relative diurnal distribution of flies caught revealed a bimodal peak between 10:00-11:00hr and 15:00-16:00hr in both communities. Monthly data on abundance also revealed a bimodal peak in the study sites in June and September with a significant difference (p<0.05) in the abundance across the months. Highest biting rate was recorded in June (Opeji=4492.5; Imala-Odo=780) while August recorded the lowest monthly biting rates (Opeji=284; Imala-Odo=62). The relationship between flies abundance and climatic data showed no significant relationship in both communities (p>0.05). This study revealed that there is high abundance of forest black flies during wet season which have epidemiological implication on humans living in these areas and efforts should be made towards constant monitoring of the siblings species