Prevalence intensity and the factors associated with intestinal schistosomiasis in preschool children in Ukerewe island Mwanza region Tanzania

Abstract

Recent evidence indicates that preschool children (PSC) living in S. mansoni highly endemic areas are at similar risk of schistosomiasis infection and morbidity as their school aged counterparts. Recognizing this fact, the World Health Organization (WHO) is considering including this age group in control programs using mass drug administration (MDA), in the highly endemic areas. However, detailed epidemiological information on S. mansoni infection among PSC is lacking for many endemic areas, including in Tanzania. This study was conducted to determine the prevalence and intesnsity of S. mansoni infection among PSC in Lake Victoria’s Ukerewe Island, in North-Western Tanzania, and the factors associated with infection in this age group.This was a cross-sectional study involving 400 PSC aged 1- 6 years of age. The Kato-Katz (K-K) technique and the point of care circulating cathodic antigen (CCA) immunodiagnostic test were used to diagnose S. mansoni infection in stool and urine samples, respectively, and a pre-tested questionnaire was used to collect demographic data and water contact behaviour of the children through their parents/guardians. GPS data of the households of study participants and water contact points nearest to their homesteads was obtained. Data collected was entered into data collection forms, notebooks, and then transferred into the Microsoft Excel software for consistency data checks and data cleaning. Analysis was done using STATA 13 and ArcGIS ArcMap 10.2.2. Chi squared test for difference in frequencies were performed. Potential associations were assessed at a bivariate level; then, factors with P-value <0.2 were entered into multivariate model. Sex and age group term were entered as a priori into the multivariate model. Stepwise backward logistic regression was used to determine whether these variables were independent factors of S. mansoni. Independent risk factors of faecal egg counts were identified in a linear regression model using a log-transformed egg per gram of faeces (epg) as outcomes variable and social demographic factors as explanatory variables. The odd ratios of each of the risk factors associated with faecal egg counts were obtained by taking the antilogarithm of the regression coefficient. Based on the K-K technique, 44.4% (95% CI: 39.4-49.4) preschool children were infected with S. mansoni and the overall geometric mean eggs per gram of faeces (GM-epg) was 110.6 epg with 38.2% and 14.7% having moderate and heavy intensity infections respectively. Based on the CCA, 80.1%, (95% CI: 76.0-84.0) were infected if a trace was considered positive, and 45.9%, (95% CI: 40.9-50.9), were infected if a trace was considered negative. Reported history of lake visit (AOR= 2.31, 95% CI 1.06 - 5.01, P<0.03) and the proximity to the lake shore (<500m) (AOR= 2.09, 95% CI: 1.05-4.14, P<0.03) were significantly associated with S. mansoni infection. Reported lake visit frequency (4 -7days/week) was associated with heavy intensities of S. mansoni infection (P<0.00).The prevalence of S. mansoni infection in the study population using K-K and CCA trace is negative was moderate. The frequency of lake visits, the proximity to the lake shore were associated with the infection of S. mansoni and its intensity. These findings call for the need to include the PSC in MDA programs, public health education and provision of safe water for bathing.