Endemic Paragonimus infection in upper Igwun Basin, Nigeria: a preliminary report on a renewed outbreak.

In a 24-month longitudinal study on a renewed outbreak of Paragonimus infection in Igwun Basin, Nigeria 1973 individuals were examined. A total of 332 (16.8%) individuals were found infected with Paragonimus uterobilateralis. There was evidence of increasing annual prevalence rates from 15.0% in 1983 to 16.7% in 1984, and 18.7% in 1985. Infection was present in all age groups, with prevalence of 18.9% in males and 14.5% in females. 12.3% of the infections were of high intensity, over 100 eggs in 5 ml of sputum; 20.5% were moderate infections, 50-100 eggs in 5 ml of sputum; the remaining 67.2% were of low intensity, less than 50 eggs in 5 ml of sputum. The increasing annual prevalence rates and intensity of infection resulted from increased crab consumption. The commonest crab was Sudanautes africanus, whose population and level of infection with metacercariae showed seasonal fluctuations with peaks during the dry season months. There was evidence that snails of the genus Melania are involved in the transmission of P. uterobilateralis in the area.