Infectivity and transmission dynamics of simulium damnosum s. 1 around Owena dam (Ondo State).

A twelve month study on the infectivity and transmission dynamics of simulium damnosum s.1 around Owena dam was conducted as part of a longitudinal study of onchocerciasis in the community living in the vicinity of the dam. A total of 3,133 flies (49.6% nilliparous, 50.4% parous) were caught during the period of study and dissected. The annual biting rate per year was recorded as 33,663 flies while the parous biting rate was recorded as 16,780 for these flies. 0.4% of the flies were infected with Onchocerca volvulus larvae while 0.3% of these had the infective larvae. However 0.3% of the nulliparous flies were found to be infected with mermithid larvae and 0.5% with trematodes. The biting activity of the fly was observed to be bimodal with a small peak in the morning hours (10.00-11.00 hours) and a more pronounced peak in the evening (16.00-17.00 hours). An annual transmission potential of 109 larvae per man per year was recorded with 64% of the infection being recorded during the early dry season when the parous rate was very high. The implications of these findings to the study area are discussed.