Studies on the distribution, infective rate and relative abundance of copepods-Cyclops, the intermediate host of guinea worm (Dracumculus medinensis) were carried out in 42 sources of drinking water. These were sources commonly used by the residents in 18 randomly selected guinea worm endemic communities in three Local Governments namely Ekiti West; Ekiti South West ado Ekiti Central (Ado-Local Government), all in Ekiti State. 21,405 cyclops were examined between 2003/2004, out of which 8.0% were found infected with larvae of Dracunculus medinensis and during 2004/2005, 5.7% of 11,982 cyclops were infected.

The density of infected Cyclops was highest in April, 2004, 11.1% with a density of 469/litre while infected Cyclops population was highest in March, 2005, 8.3% with a density of 334/litre.

The mean intensity of infection for 2003/2004 was 95.4±87.4 while that for 2004/2005 was 37.6±20.1. There wes a significant (P<0.05) yearly reduction in the percentage/population of infected Cyclops between 2003/2004 and 2004/2005. There was a positive correlation (r=0.63; P<0.05) between vector infectivity and prevalence of the disease in the study area. Three species of Cyclops encountered are Cyclops leuckarti. Thermocyclops inopinus and Halicyclops. These are vectors of guinea worm that play a significant role in the transmission of the disease.