Prevalence and intensity of Schistosoma haematobium and S. mansoni infection in Qalyub, Egypt.

We report the preliminary findings of a comprehensive schistosomiasis survey in the Qalyub region of the Nile Delta. A systematic sample of households in eight villages was studied, and 8,712 individuals submitted stool and urine specimens for parasitologic examinations. The prevalence of Schistosoma mansoni infection (40.5%) was much higher than that reported previously in this area, and the prevalence of S. haematobium (27%) was much lower. The geometric mean egg output for both parasites was surprisingly low. The apparent increase in S. mansoni infection may be largely due to the use of a very sensitive parasitologic technique, but the decrease in S. haematobium prevalence is unexplained. Preliminary results of snail surveys, however, indicate a profound decrease in the population levels of Bulinus species, a phenomenon which may be related to ecological changes since construction of the Aswan High Dam.