Urban schistosomiasis: Morbidity, sociodemographic characteristics and water contact patterns predictive of infection

Abstract

Background. Schistosomiasis (Schistosoma mansoni) is classically described as a rural disease that occurs in areas with poor sanitary conditions. This cross-sectional study was undertaken in a suburban area of a large industrialized city in Brazil (Belo Horizonte), aiming at examining epidemiological characteristics of schistosomiasis in an urban setting. Methods. A simple random sample of 658/1896 dwellings was selected and 3049/3290 (92.7%) residents were submitted to stool examination. Of 518 eligible infected cases and 518 uninfected controls, 87.1% and 89.8% participated in the study, respectively. Results. The prevalence of S. mansoni infection was 20%, predominantly low egg counts in stools; no cases of splenomegaly were found. Signs and symptoms associated with infection were bloody stools (odds ratio [OR] = 8.0) and hardened palpable liver at the middle clavicular and at the middle sternal line (OR = 5.5 and 8.0, respectively). Sociodemographic variables and water contacts predictive of infection were age (10-19 and ≤ 20 yrs; OR = 7.1 and 3.3, respectively), gender (male; OR = 3.1), contacts for swimming and/or playing (twice a month or less and more than twice a month; OR = 2.2 and 3.0, respectively) and residence in Belo Horizonte (born in the City; OR = 2.5). Ninety per cent of dwellings had a piped water supply; no association between water supply and infection was found. Conclusion. Our results emphasize the need for schistosomiasis control measures focusing on water contacts for leisure purposes in this industrialized urban area.