Abstract
The prevalence, intensity and incidence of schistosomiasis in the human population was investigated in 20 sites in the Hijaz highlands and in 10 sites in the Tihamah lowlands. The prevalence rate of S. mansoni in a total of 3092 persons examined in the Hijaz highlands ranged between 0.5 and 22.6% with a mean of 5.98%: males having a greater prevalence than females. In the Hijaz highlands S. haematobium was not recorded. In the Tihamah lowlands S. mansoni was recorded at one site with a prevalence of 0.53% and S. haematobium at two sites with a prevalence of 0.55% and 1.13%. A total of 1771 persons were examined in the Tihamah. The prevalence of S. mansoni in males was maximal in the age group 11-15 years with a decline afterwards and another slight increase at 31 + years old. In females S. mansoni was low in prevalence at early life (1-20 years) and increased from 21 + years onwards. As to intensity of infection (eggs/g stool) 54.05%, 34.05% and 11.9% of the infected persons had light, moderate and heavy intensities. The mean incidence rate of S. mansoni in four sites was 2.94%. The implications of these epidemiological findings in relation to control are discussed.