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. 2018 Aug 25;11(1):481.
doi: 10.1186/s13071-018-3064-5.

Geographical and behavioral risks associated with Schistosoma haematobium infection in an area of complex transmission

Teckla Angelo  1   2 , Joram Buza  3 , Safari Methusela Kinung'hi  4 , Henry Curtis Kariuki  5 , Joseph Rogathe Mwanga  4 , David Zadock Munisi  3 , Shona Wilson  6
Affiliations

Geographical and behavioral risks associated with Schistosoma haematobium infection in an area of complex transmission

Teckla Angelo et al. Parasit Vectors. .

Abstract

Background: Schistosoma haematobium infection in endemic areas varies depending on the nature and complexity of the transmission networks present. Studies of micro-geographical transmission of S. haematobium infection indicate that discrepancy in prevalence between households is associated with diverse water contact behaviors and transmission that is restricted to particular sites harboring snail intermediate hosts. Detection of variations in the transmission sources with complex transmission networks of water bodies is required for optimization of malacological control. Longitudinal parasitological and malacological surveys were conducted to investigate geographical variations in transmission of urogenital schistosomiasis in Ikingwamanoti village, Shinyanga District, Tanzania.

Methods: Urine samples were collected at baseline and follow-up time points from 282 school-aged children and examined microscopically for the presence of S. haematobium eggs. Malacological surveys involved collection of Bulinus nasutus every month from 30 sites. Snails were examined for patent infections. Global positioning system was used to map household distances from S. haematobium transmission sites, while water contact behavior was assessed using a questionnaire.

Results: Schistosoma haematobium infection was observed to be prevalent among older children (12-14 years) compared to younger groups prior to treatment, but no significant difference in infection prevalence was observed at one-year. Boys were highly infected than girls at both time points. No spatial influence was observed between children's infection and the distance from child's residence to the nearby snail habitats nor was any significant association observed between children's reported water contact behavior with S. haematobium infection. However, malacological surveys with cercarial shedding combined with GPS data detected significant variation among different water sources in the transmission of S. haematobium with children living in households near to ponds with high B. nasutus populations having the highest prevalence of infection.

Conclusions: Interaction between malacological surveys with cercarial shedding combined with GPS mapping in endemic settings can help detection of transmission sources even in areas with complex transmission networks. Subsequent studies are needed to determine whether the combination of GPS mapping and parasitology screens can aid the detection of transmission hotspots across varied transmission settings to enhance schistosomiasis control programmes.

Keywords: GPS; Malacological surveys; Urogenital schistosomiasis; Water contact behavior.

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Conflict of interest statement

Ethics approval and consent to participate

This study was approved by the Medical Research Coordination Committee (MRCC) of the National Institute for Medical Research (NIMR), Tanzania (ethics clearance certificate no. NIMR/HQ/R.8a/Vol.IX/2107) and the University of Cambridge Human Biology Research Ethics Committee (HBREC.2015.28). The purpose of the study and procedures for sample collection were explained to the school children, adults in the communities, local leaders, school administrators, education personnel, teachers and health personnel before requesting for urine samples. Inclusion criteria for school children were based on the provision of assent for participation. Parents/guardians of school children attending Ikingwamanoti primary school were asked to provide signed/marked consent for their children to be included in the study. Only children who assented to participate and had parental or guardian’s consent were eligible for inclusion. Each child recruited into the study was assigned with a unique identification number that linked samples and results. All data relating to the study participants were entered into a confidential file to which only members of the research team had access.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Household allocation to snail site and mean household intensity of infection of S. haematobium infection. The assignment of households to central coordinates of the nearest habitat is shown, as are the mean pre-treatment infection intensities, grouped according to no infection, light infection (1–49 eggs/10 ml of urine) or high infection intensity (≥ 50 eggs/10 ml of urine), recorded for each household
Fig 2
Fig 2
Prevalence of S. haematobium in school children in relation to intermediate host site, numbers and patent infections. Scatter plots of the prevalence of S. haematobium infection within school children assigned to their nearest snail habitat, indicated numerically, against the accumulated snail count for that habitat (a), or the accumulated number of snails that shed Schistosoma spp. cercariae (b)
See this image and copyright information in PMC

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