Molecular epidemiology and phylogeography of Schistosoma mansoni around Lake Victoria.

Intestinal schistosomiasis continues to be a major public health problem in sub-Saharan Africa, and is endemic in communities around Lake Victoria. Interest is growing in the molecular evolution and population genetic structure of Schistosoma mansoni and we describe a detailed analysis of the molecular epidemiology and phylogeography of S. mansoni from Lake Victoria. In total, 388 cytochrome oxidase 1 (COI) sequences were obtained from 25 sites along the Ugandan, Tanzanian and Kenyan shorelines of Lake Victoria, and 122 unique barcodes were identified; 9 corresponded to previously discovered barcodes from Lakes Victoria and Albert. A subset of the data, composed of COI sequences from miracidia from 10 individual children, was used for population genetics analyses; these results were corroborated by microsatellite analysis of 4 isolates of lab-passaged adult worms. Overall, 12 barcodes were found to be shared across all 3 countries, whereas the majority occurred singly and were locally restricted. The population genetics analyses were in agreement in revealing high diversity at the level of the human host and negligible population structuring by location. The lack of correlation between genetic distance and geographical distance in these data may be attributed to the confounding influence of high intra-individual diversity as well as human migration between communities.

Performance of circulating cathodic antigen (CCA) urine-dipsticks for rapid detection of intestinal schistosomiasis in schoolchildren from shoreline communities of Lake Victoria.

ABSTRACT: For disease surveillance and mapping within large-scale control programmes, RDTs are becoming popular. For intestinal schistosomiasis, a commercially available urine-dipstick which detects schistosome circulating cathodic antigen (CCA) in host urine is being increasingly applied, however, further validation is needed. In this study, we compared the CCA urine-dipstick test against double thick Kato-Katz faecal smears from 171 schoolchildren examined along the Tanzanian and Kenyan shorelines of Lake Victoria. Diagnostic methods were in broad agreement; the mean prevalence of intestinal schistosomiasis inferred by Kato-Katz examination was 68.6% (95% confidence intervals (CIs) = 60.7-75.7%) and 71.3% (95% CIs = 63.9-78.8%) by CCA urine-dipsticks. There were, however, difficulties in precisely 'calling' the CCA test result, particularly in discrimination of 'trace' reactions as either putative infection positive or putative infection negative, which has important bearing upon estimation of mean infection prevalence; considering 'trace' as infection positive mean prevalence was 94.2% (95% CIs = 89.5-97.2%). A positive association between increasing intensity of the CCA urine-dipstick test band and faecal egg count was observed. Assigning trace reactions as putative infection negative, overall diagnostic sensitivity (SS) of the CCA urine-dipstick was 87.7% (95% CIs = 80.6-93.0%), specificity (SP) was 68.1% (95% CIs = 54.3-80.0%), positive predictive value (PPV) was 86.1% (95% CIs = 78.8-91.7%) and negative predictive value (NPV) was 71.1% (95% CIs = 57.2-82.8%). To assist in objective defining of the CCA urine-dipstick result, we propose the use of a simple colour chart and conclude that the CCA urine-dipstick is a satisfactory alternative, or supplement, to Kato-Katz examination for rapid detection of intestinal schistosomiasis.

Community's willingness to pay for a school-based chemotherapy programme to control morbidity due to schistosomiasis and soil-transmitted helminthiasis in children in rural Tanzania.

A cross-sectional questionnaire survey was conducted on a random sample of 523 households having at least one child attending primary school in 3 villages in Buchosa Division, Sengerema District, Tanzania. The aim was to determine the community's willingness to pay (WTP) for a school-based chemotherapy programme to control morbidity due to schistosomiasis and soil-transmitted helminthiasis (STH) in schoolchildren and identify socio-economic and cultural factors influencing community's WTP. Results showed that households WTP for a school-based chemotherapy programme varied from Tanzanian Shillings (TShs.) 0-20,000 (US dollars 0-25) per child per year. The community's WTP (median of households WTP) was TSh. 1,000 (US dollars 1.25). The community was also willing to pay extra TSh.100 (US dollars 0.125) per year to cover for the cost of schoolchildren whose parents were unable to pay or who could pay less than the community's WTP. Age of household head and number of schoolchildren in a household had a negative effect on the household's willingness to pay. Households with children in expensive schools had high willingness to pay for the intervention package to control worms in their children. This was also observed in households keeping animals (cattle, goats, sheep, chiken, ducks) and those who cultivated a number of cash crops.