Unabated schistosomiasis transmission in Erinle River Dam, Osun State, Nigeria: evidence of neglect of environmental effects of development projects.

The status of Schistosoma haematobium infection around Erinle Dam in Osun State, Nigeria, was investigated 10 years after the disease was first reported in the area. School children in two rural communities (Ilie and Oba-Ile) were examined for infection and the lake surveyed for snail intermediate host species between March 2000 and February 2001. Overall infection rate among 320 children examined in both communities was 46.6% (52.3% in Ilie and 43.0% in Oba-Ile). Mean intensity of infection ranged between 144.2 +/- 389 and 156.5 +/- 378 eggs per 10 ml urine in Ilie and Oba-Ile respectively (overall: 148.8 +/- 378 eggs per 10 ml urine). Prevalence and intensity were comparable in both communities and between boys and girls, but varied significantly (P < 0.05) with age. Bulinus globosus identified by a previous study as the local intermediate host species was found to be abundant in the lake and occurred throughout the year, in contrast to seasonal occurrence reported previously. Both prevalence and intensity of infection also increased significantly over the levels reported 10 years earlier. These results are clear indications that transmission has remained unabated in the lake during the period. The need for urgent and effective national control programme to reduce the public health importance of schistosomiasis in Erinle and other dams in Nigeria was discussed.