Dracontiasis in the Igwun River Basin, Nigeria: its distribution, epidemiology, and transmission dynamics.

In a cross-sectional dracontiasis survey of the Igwun Basin, Nigeria, 879 persons from seven communities were examined. Ninety-five (10.8%) had dracontiasis blisters and ulcers. Male prevalence of 14.9% was significantly higher (P less than 0.001) than the female prevalence of 6.9%. Infection increased with age, rising from 2% in 1-4 years old children to 15.8% in the 35-44 years old adults. Sixty-five percent of infected males had blisters, 34.4% had ulcers. Among females, 48.4% had blisters, 51.6% had ulcers. Among the males, blisters and ulcers showed seasonal variations, with 80% cases of blisters between November and April, and 20% between June and October. Seasonal morbidity pattern in females did not show any significant variation (P greater than 0.20). The density of cyclopoid copepods increased in the dry season in relation to decreasing rainfall. The highest cyclops count was 18 cyclops per litre of water recorded between January and February, while the lowest was zero recorded in July in some areas. The infection rates of cyclops rose from 10% in November to a peak value of 20% between January and February, with the lowest rate of 5% in July. Larval burden of cyclops also rose from 3L3's/cyclops in June, to 5L3's/cyclops in January. Dracontiasis appears to be a relatively new disease in the area, and its spread has been enhanced by the interaction of human behavioural, and parasite-vector ecological factors which are seasonally modulated.