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New insights into the molecular epidemiology and population genetics of Schistosoma mansoni in Ugandan pre-school children and mothers.

ABSTRACT: Significant numbers of pre-school children are infected with Schistosoma mansoni in sub-Saharan Africa and are likely to play a role in parasite transmission. However, they are currently excluded from control programmes. Molecular phylogenetic studies have provided insights into the evolutionary origins and transmission dynamics of S. mansoni, but there has been no research into schistosome molecular epidemiology in pre-school children. Here, we investigated the genetic diversity and population structure of S. mansoni in pre-school children and mothers living in lakeshore communities in Uganda and monitored for changes over time after praziquantel treatment. Parasites were sampled from children (<6 years) and mothers enrolled in the longitudinal Schistosomiasis Mothers and Infants Study at baseline and at 6-, 12- and 18-month follow-up surveys. 1347 parasites from 35 mothers and 45 children were genotyped by direct sequencing of the cytochrome c oxidase (cox1) gene. The cox1 region was highly diverse with over 230 unique sequences identified. Parasite populations were genetically differentiated between lakes and non-synonymous mutations were more diverse at Lake Victoria than Lake Albert. Surprisingly, parasite populations sampled from children showed a similar genetic diversity to those sampled from mothers, pointing towards a non-linear relationship between duration of exposure and accumulation of parasite diversity. The genetic diversity six months after praziquantel treatment was similar to pre-treatment diversity. Our results confirm the substantial genetic diversity of S. mansoni in East Africa and provide significant insights into transmission dynamics within young children and mothers, important information for schistosomiasis control programmes.

SUBMITTER: Betson M

PROVIDER: S-EPMC3861247 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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New insights into the molecular epidemiology and population genetics of Schistosoma mansoni in Ugandan pre-school children and mothers.

Betson Martha M Sousa-Figueiredo Jose C JC Kabatereine Narcis B NB Stothard J Russell JR

PLoS neglected tropical diseases 20131212 12

Significant numbers of pre-school children are infected with Schistosoma mansoni in sub-Saharan Africa and are likely to play a role in parasite transmission. However, they are currently excluded from control programmes. Molecular phylogenetic studies have provided insights into the evolutionary origins and transmission dynamics of S. mansoni, but there has been no research into schistosome molecular epidemiology in pre-school children. Here, we investigated the genetic diversity and population ...[more]

PMID: 24349589

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Project description:BackgroundAnnual mass drug administration with praziquantel has reduced schistosomiasis transmission in some highly endemic areas, but areas with persistent high endemicity have been identified across sub-Saharan Africa, including Uganda. In these areas many children are rapidly reinfected post treatment, while some children remain uninfected or have low-intensity infections. The aim of this mixed-methods study was to better understand variation in water contact locations, behaviours and infection risk in school-aged children within an area with persistent high endemicity to inform additional control efforts.MethodsData were collected in Bugoto, Mayuge District, Uganda. Two risk groups were identified from a longitudinal cohort, and eight children with no/low-intensity infections and eight children with reinfections were recruited. Individual structured day-long observations with a focus on water contact were conducted over two periods in 2018. In all identified water contact sites, four snail surveys were conducted quarterly over 1 year. All observed Biomphalaria snails were collected, counted and monitored in the laboratory for Schistosoma mansoni cercarial shedding for 3 weeks.ResultsChildren came into contact with water for a range of purposes, either directly at the water sources or by coming into contact with water collected previously. Although some water contact practices were similar between the risk groups, only children with reinfection were observed fetching water for commercial purposes and swimming in water sources; this latter group of children also came into contact with water at a larger variety and number of sites compared to children with no/low-intensity infection. Households with children with no/low-intensity infections collected rainwater more often. Water contact was observed at 10 sites throughout the study, and a total of 9457 Biomphalaria snails were collected from these sites over four sampling periods. Four lake sites had a significantly higher Biomphalaria choanomphala abundance, and reinfected children came into contact with water at these sites more often than children with no/low-intensity infections. While only six snails shed cercariae, four were from sites only contacted by reinfected children.ConclusionsChildren with reinfection have more high-risk water contact behaviours and accessed water sites with higher B. choanomphala abundance, demonstrating that specific water contact behaviours interact with environmental features to explain variation in risk within areas with persistent high endemicity. Targeted behaviour change, vector control and safe water supplies could reduce reinfection in school-aged children in these settings.

Project description:BackgroundIn Ghana, pre-school-aged children (PSAC) are at risk of intestinal schistosomiasis and are living in need of praziquantel treatment. To better assess the infection burden within this vulnerable demographic group, we have provided a comparative assessment of the prevalence of Schistosoma mansoni in pre-school-aged children by urine circulating cathodic antigen (CCA) dipsticks, real-time PCR Taqman® faecal assays and Kato-Katz coproscopy.MethodsIn all, 190 pre-school-aged children were sampled from three endemic communities (viz. Tomefa, Torgahkope/Adakope, and Manheam) around Weija dam, Southern Ghana. Fresh stool and urine samples were collected from all participants for diagnosis.ResultsAmong all the three communities, the urine-CCA assay recorded the highest prevalence values of 90.5% (95% CI 80.4-96.4), 87.9% (95% CI 76.7-95), and 81.2% (95% CI 69.9-89.6) in Tomefa, Torgahkope/Adakope, and Manheam respectively. Prevalence by real-time PCR was 50% (95% CI 35.5-64.5), 8% (95% CI 2.2-19.2) and 16.7% (95% CI 8.3-28.5), while by Kato-Katz was 55.6% (95% CI 42.5-68.1), 8.6% (95% CI 2.9-19) and 11.6% (95% CI 5.1-21.6) respectively. Children aged 1 year and over were found to be positive with the urine-CCA assay; by the ages of 3-4, over 50% were urine-CCA patent. The sensitivity and specificity of the POC-CCA dipsticks, when compared against the combined results of Kato-Katz/TaqMan results was found to be 84.1% (95% CI = 72.7-92.1) and 12.9% (95% CI = 6.6-22) respectively.ConclusionsWe propose that the urine-CCA dipstick may be a useful rapid diagnostic tool to estimate the prevalence of intestinal schistosomiasis in PSAC, particularly in rapid identification of at-risk areas. However, our assessment has shown that it possible to record false positives when compared to combined Kato-Katz and qPCR results. To guide PSAC praziquantel treatment needs, we propose the urine CCA assay should be included in routine surveillance of intestinal schistosomiasis alongside other diagnostics such as Kato-Katz and urine filtration.

Dataset Information

New insights into the molecular epidemiology and population genetics of Schistosoma mansoni in Ugandan pre-school children and mothers.

Publications

New insights into the molecular epidemiology and population genetics of Schistosoma mansoni in Ugandan pre-school children and mothers.

Similar Datasets

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