Human community ecology of urinary schistosomiasis in relation to snail vector bionomics in the Igwun River Basin of Nigeria.

In a 15-months filed study of the human community ecology of urinary schistosomiasis 15.0% prevalence rate was recorded in 1,625 individuals examined. 37.0% of infected individuals had infections of low intensity. 34.0% were of moderate intensity, while 28.7% had high intensity in infections. Male prevalence of 16.7% was not statistically different (P less than 0.05) from the female prevalence of 13.3%. The population of the Bulinus snail intermediate host showed seasonal fluctuations with a peak in May, and a trough in January. Infection rates of snails rose gradually from 60% in February to 75% in May. Cercarial burdens of snails rose from 500 cercariae per snail per month to a peak count of 900 cercariae per snail per month in June. Water contact activities were either complete and long term, partial and medium term or limited and short term. Age, sex, and occupation were important determinants of the type, duration and period of water contact activities. Results also suggest that high exposure indices were related to high infection prevalence and intensity.