Necator americanus infection: a longitudinal study of an urban area in Nigeria.

A longitudinal study was carried out in Owerri, capital of Imo State, Nigeria, to assess the pattern of Necator americanus infection during a 27-month period. The mean annual prevalence fell from 59.0% in 1978, to 55.5% in 1979 and 51.1% in 1980. The egg count (apparent intensity of infection) fell in a similar pattern. Maximum and minimum conversion rates were 55.2 and 13.7%, respectively, and conversion rates fell by approximately 20% between 1979 and 1980. The highest reversion rate was 55.0% between 1979 and 1980. The population density of available third-stage larvae fluctuated seasonally and this was significant in determining the pattern of infection.