Abstract
A study of the social, environmental and parasitological factors involved in the transmission of schistosomiasis among 1834 residents of a small settlement within an agricultural establishment near Yola, Nigeria, was carried out between June 1991 and May 1992. Water-contact rates and the prevalences of urinary schistosomiasis and intestinal schistosomiasis (40·0% of all contacts, 98% and 79%, respectively) were highest among children of 5–12 years, who were also the major contributors to the contamination of the Lake Geriyo environment with faeces and urine. The frequency and duration of water contact followed a seasonal pattern and seemed to be influenced by physiological and social needs such as defecation, urination and avoidance of harsh weather conditions. The interplay between a need for water contact, sanitation, freshwater snails and a supportive environment ensures a recycling of parasites within the studied community. This, in turn, helps to maintain a parasite bank from which infection is probably spread to other areas of the state. The present study is part of a series, on the dynamics of schistosomiasis transmission, which began with a study of the ecology of the freshwater snails in the same area.