EPIDEMIOLOGICAL STUDY OF SCHISTOSOMA HAEMATOBIUM INFECTION IN A COASTAL AREA OF KENYA-THE IMPORTANCE OF WATER CONTACT PATTERNS IN RELATION TO S. HAEMATOBIUM INFECTION

Water contact observation and urine examination were carried out on a population in an endemic area of Schistosoma haematobium infection, Mwachinga, Kwale district, Kenya. The change in the mean level of water contact with age and the ageprevalence or age-intensity distribution of S. haematobium infection showed similar trends, but not a direct quantitative relationship. Therefore, a mathematical model was applied in the attempt to analyze the relationship between the intensity of S. haematobium infection and the level of water contact. The worm burden, number of paired worms and proportion of hosts with paired worms were estimated from the level of water contact, annual incidence, and the proposed life-span of S. haematobium by using an immigrationdeath model on the basis of simple assumptions. These estimated values were compared with the observed prevalence and intensity of infection. The results showed a linear correlation between observed data and estimated values. We conclude that the characteristic shape of the age-egg output curve for S. haematobium in the community is satisfactorily explained solely in terms of 'the change in water contact with age.