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Pennance T, Calvelo J, Tennessen JA, Burd R, Cayton J, Bollmann SR, Blouin MS, Spaan JM, Hoffmann FG, Ogara G, Rawago F, Andiego K, Mulonga B, Odhiambo M, Loker ES, Laidemitt MR, Lu L, Iriarte A, Odiere M, Steinauer ML. The genome and transcriptome of the snail Biomphalaria sudanica s.l.: Immune gene diversification and highly polymorphic genomic regions in an important African vector of Schistosoma mansoni. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.01.565203. [PMID: 37961413 PMCID: PMC10635097 DOI: 10.1101/2023.11.01.565203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Background Control and elimination of schistosomiasis is an arduous task, with current strategies proving inadequate to break transmission. Exploration of genetic approaches to interrupt Schistosoma mansoni transmission, the causative agent for human intestinal schistosomiasis in sub-Saharan Africa and South America, has led to genomic research of the snail vector hosts of the genus Biomphalaria. Few complete genomic resources exist, with African Biomphalaria species being particularly underrepresented despite this being where the majority of S. mansoni infections occur. Here we generate and annotate the first genome assembly of Biomphalaria sudanica sensu lato, a species responsible for S. mansoni transmission in lake and marsh habitats of the African Rift Valley. Supported by whole-genome diversity data among five inbred lines, we describe orthologs of immune-relevant gene regions in the South American vector B. glabrata and present a bioinformatic pipeline to identify candidate novel pathogen recognition receptors (PRRs). Results De novo genome and transcriptome assembly of inbred B. sudanica originating from the shoreline of Lake Victoria (Kisumu, Kenya) resulted in a haploid genome size of ~944.2 Mb (6732 fragments, N50=1.067 Mb), comprising 23,598 genes (BUSCO=93.6% complete). The B. sudanica genome contains orthologues to all described immune genes/regions tied to protection against S. mansoni in B. glabrata. The B. sudanica PTC2 candidate immune genomic region contained many PRR-like genes across a much wider genomic region than has been shown in B. glabrata, as well as a large inversion between species. High levels of intra-species nucleotide diversity were seen in PTC2, as well as in regions linked to PTC1 and RADres orthologues. Immune related and putative PRR gene families were significantly over-represented in the sub-set of B. sudanica genes determined as hyperdiverse, including high extracellular diversity in transmembrane genes, which could be under pathogen-mediated balancing selection. However, no overall expansion in immunity related genes were seen in African compared to South American lineages. Conclusions The B. sudanica genome and analyses presented here will facilitate future research in vector immune defense mechanisms against pathogens. This genomic/transcriptomic resource provides necessary data for the future development of molecular snail vector control/surveillance tools, facilitating schistosome transmission interruption mechanisms in Africa.
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Affiliation(s)
- Tom Pennance
- College of Osteopathic Medicine of the Pacific - Northwest, Western University of Health Sciences, Lebanon OR, USA
| | - Javier Calvelo
- Laboratorio Biología Computacional, Departamento de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Montevideo 11600, Uruguay
| | | | - Ryan Burd
- College of Osteopathic Medicine of the Pacific - Northwest, Western University of Health Sciences, Lebanon OR, USA
| | - Jared Cayton
- College of Osteopathic Medicine of the Pacific - Northwest, Western University of Health Sciences, Lebanon OR, USA
| | | | | | - Johannie M Spaan
- College of Osteopathic Medicine of the Pacific - Northwest, Western University of Health Sciences, Lebanon OR, USA
| | - Federico G Hoffmann
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, Starkville, MS USA
| | - George Ogara
- Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), P. O. Box 1578-40100, Kisumu, Kenya
| | - Fredrick Rawago
- Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), P. O. Box 1578-40100, Kisumu, Kenya
| | - Kennedy Andiego
- Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), P. O. Box 1578-40100, Kisumu, Kenya
| | - Boaz Mulonga
- Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), P. O. Box 1578-40100, Kisumu, Kenya
| | - Meredith Odhiambo
- Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), P. O. Box 1578-40100, Kisumu, Kenya
| | - Eric S Loker
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A
| | - Martina R Laidemitt
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A
| | - Lijun Lu
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A
| | - Andrés Iriarte
- Laboratorio Biología Computacional, Departamento de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la República, Montevideo 11600, Uruguay
| | - Maurice Odiere
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, Starkville, MS USA
| | - Michelle L Steinauer
- College of Osteopathic Medicine of the Pacific - Northwest, Western University of Health Sciences, Lebanon OR, USA
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Andrus PS, Stothard JR, Wade CM. Seasonal patterns of Schistosoma mansoni infection within Biomphalaria snails at the Ugandan shorelines of Lake Albert and Lake Victoria. PLoS Negl Trop Dis 2023; 17:e0011506. [PMID: 37578945 PMCID: PMC10424865 DOI: 10.1371/journal.pntd.0011506] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 07/06/2023] [Indexed: 08/16/2023] Open
Abstract
Intestinal schistosomiasis is hyperendemic in many sub-Saharan African countries. In Uganda, it is endemic at both Lake Albert (LA) and Lake Victoria (LV) and caused by S. mansoni that uses Biomphalaria snails as obligatory intermediate snail hosts. To shed light on local patterns of infection, we utilised two PCR-based methods to detect S. mansoni within Biomphalaria spp. as collected at the Ugandan shorelines of Lake Albert and Lake Victoria from 2009-2010. Overall, at our Lake Albert sites, the mean infection prevalence was 12.5% (15 of 120 snails), while at our Lake Victoria sites the prevalence was 5% (3 of 60 snails). At our Lake Albert sites, the highest infection prevalence of 13.3% (8 of 60 snails) was at Walukuba, while at our Lake Victoria sites, the highest infection prevalence of 10% (2 of 20 snails) was at Lwanika. Three species of Biomphalaria, B. pfeifferi, B. stanleyi and B. sudanica, were identified at our Lake Albert collection sites, while only a single species, B. choanomphala, was identified at our Lake Victoria collection sites. Biomphalaria stanleyi (2 of 20 snails; 15%) had the highest infection prevalence, followed by B. sudanica (5 of 60 snails; 13.3%), B. pfeifferi (4 of 40 snails; 10%) and B. choanomphala (3 of 60 snails; 5%). Of the Biomphalaria species identified, B. choanomphala had the highest haplotype (gene) diversity score, followed by B. stanleyi, B. sudanica and B. pfeifferi. Sites with a higher mean prevalence of S. mansoni infection had higher intra-species haplotype diversity scores than sites with a lower mean prevalence. The wet seasons (LA: 13.3%; LV: 8.7%) had a consistently higher mean infection prevalence of S. mansoni than the dry seasons (LA: 9.5%; LV: 5%) for all species and all sites tested at both Lake Albert (n = 480) and Lake Victoria (n = 320), though the difference was not statistically significant.
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Affiliation(s)
- Peter S. Andrus
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - J. Russell Stothard
- Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Christopher M. Wade
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
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3
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Spaan JM, Pennance T, Laidemitt MR, Sims N, Roth J, Lam Y, Rawago F, Ogara G, Loker ES, Odiere MR, Steinauer ML. Multi-strain compatibility polymorphism between a parasite and its snail host, a neglected vector of schistosomiasis in Africa. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2023; 3:100120. [PMID: 37128285 PMCID: PMC10147961 DOI: 10.1016/j.crpvbd.2023.100120] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 03/23/2023] [Indexed: 05/03/2023]
Abstract
Interactions between Schistosoma mansoni and its snail host are understood primarily through experimental work with one South American vector species, Biomphalaria glabrata. However, 90% of schistosomiasis transmission occurs in Africa, where a diversity of Biomphalaria species may serve as vectors. With the long-term goal of determining the genetic and ecological determinants of infection in African snail hosts, we developed genetic models of Biomphalaria sudanica, a principal vector in the African Great Lakes. We determined laboratory infection dynamics of two S. mansoni lines in four B. sudanica lines. We measured the effects of the following variables on infection success and the number of cercariae produced (infection intensity): (i) the combination of parasite and snail line; (ii) the dose of parasites; and (iii) the size of snail at time of exposure. We found one snail line to be almost completely incompatible with both parasite lines, while other snail lines showed a polymorphism in compatibility: compatible with one parasite line while incompatible with another. Interestingly, these patterns were opposite in some of the snail lines. The parasite-snail combination had no significant effect on the number of cercariae produced in a successful infection. Miracidia dose had a strong effect on infection status, in that higher doses led to a greater proportion of infected snails, but had no effect on infection intensity. In one of the snail-schistosome combinations, snail size at the time of exposure affected both infection status and cercarial production in that the smallest size class of snails (1.5-2.9 mm) had the highest infection rates, and produced the greatest number of cercariae, suggesting that immunity increases with age and development. The strongest predictor of the infection intensity was the size of snail at the time of shedding: 1 mm of snail growth equated to a 19% increase in cercarial production. These results strongly suggest that infection status is determined in part by the interaction between snail and schistosome genetic lines, consistent with a gene-for-gene or matching allele model. This foundational work provides rationale for determining the genetic interactions between African snails and schistosomes, which may be applied to control strategies.
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Affiliation(s)
- Johannie M. Spaan
- Department of Basic Medical Sciences, Western University of Health Sciences, Lebanon, OR, USA
| | - Tom Pennance
- Department of Basic Medical Sciences, Western University of Health Sciences, Lebanon, OR, USA
| | - Martina R. Laidemitt
- Department of Biology, University of New Mexico, Albuquerque, USA
- Center for Evolutionary and Theoretical Immunology (CETI), University of New Mexico, Albuquerque, USA
| | - Nicole Sims
- Department of Basic Medical Sciences, Western University of Health Sciences, Lebanon, OR, USA
| | - Jewell Roth
- Department of Basic Medical Sciences, Western University of Health Sciences, Lebanon, OR, USA
| | - Yvonne Lam
- Department of Basic Medical Sciences, Western University of Health Sciences, Lebanon, OR, USA
| | - Fredrick Rawago
- Kenya Medical Research Institute (KEMRI), Centre for Global Health Research, Kisumu, Kenya
| | - George Ogara
- Kenya Medical Research Institute (KEMRI), Centre for Global Health Research, Kisumu, Kenya
| | - Eric S. Loker
- Department of Biology, University of New Mexico, Albuquerque, USA
- Center for Evolutionary and Theoretical Immunology (CETI), University of New Mexico, Albuquerque, USA
| | - Maurice R. Odiere
- Kenya Medical Research Institute (KEMRI), Centre for Global Health Research, Kisumu, Kenya
| | - Michelle L. Steinauer
- Department of Basic Medical Sciences, Western University of Health Sciences, Lebanon, OR, USA
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4
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Bu L, Lu L, Laidemitt MR, Zhang SM, Mutuku M, Mkoji G, Steinauer M, Loker ES. A genome sequence for Biomphalaria pfeifferi, the major vector snail for the human-infecting parasite Schistosoma mansoni. PLoS Negl Trop Dis 2023; 17:e0011208. [PMID: 36961841 PMCID: PMC10075465 DOI: 10.1371/journal.pntd.0011208] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 04/05/2023] [Accepted: 02/27/2023] [Indexed: 03/25/2023] Open
Abstract
BACKGROUND Biomphalaria pfeifferi is the world's most widely distributed and commonly implicated vector snail species for the causative agent of human intestinal schistosomiasis, Schistosoma mansoni. In efforts to control S. mansoni transmission, chemotherapy alone has proven insufficient. New approaches to snail control offer a way forward, and possible genetic manipulations of snail vectors will require new tools. Towards this end, we here offer a diverse set of genomic resources for the important African schistosome vector, B. pfeifferi. METHODOLOGY/PRINCIPAL FINDINGS Based largely on PacBio High-Fidelity long reads, we report a genome assembly size of 772 Mb for B. pfeifferi (Kenya), smaller in size than known genomes of other planorbid schistosome vectors. In a total of 505 scaffolds (N50 = 3.2Mb), 430 were assigned to 18 large linkage groups inferred to represent the 18 known chromosomes, based on whole genome comparisons with Biomphalaria glabrata. The annotated B. pfeifferi genome reveals a divergence time of 3.01 million years with B. glabrata, a South American species believed to be similar to the progenitors of B. pfeifferi which undertook a trans-Atlantic colonization < five million years ago. CONCLUSIONS/SIGNIFICANCE The genome for this preferentially self-crossing species is less heterozygous than related species known to be preferential out-crossers; its smaller genome relative to congeners may similarly reflect its preference for selfing. Expansions of gene families with immune relevance are noted, including the FReD gene family which is far more similar in its composition to B. glabrata than to Bulinus truncatus, a vector for Schistosoma haematobium. Provision of this annotated genome will help better understand the dependencies of trematodes on snails, enable broader comparative insights regarding factors contributing to susceptibility/ resistance of snails to schistosome infections, and provide an invaluable resource with respect to identifying and manipulating snail genes as potential targets for more specific snail control programs.
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Affiliation(s)
- Lijing Bu
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Lijun Lu
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Martina R Laidemitt
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Si-Ming Zhang
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Martin Mutuku
- Center for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Gerald Mkoji
- Center for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Michelle Steinauer
- College of Osteopathic Medicine of the Pacific-Northwest, Western University of Health Sciences, Lebanon, Oregon, United States of America
| | - Eric S Loker
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
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5
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Laidemitt MR, Gleichsner AM, Ingram CD, Gay SD, Reinhart EM, Mutuku MW, Oraro P, Minchella DJ, Mkoji GM, Loker ES, Steinauer ML. Host preference of field‐derived
Schistosoma mansoni
is influenced by snail host compatibility and infection status. Ecosphere 2022; 13. [PMID: 36285193 PMCID: PMC9592064 DOI: 10.1002/ecs2.4004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Schistosome parasites cause a chronic inflammatory disease in humans, and recent studies have emphasized the importance of control programs for understanding the aquatic phases of schistosomiasis transmission. The host-seeking behavior of larval schistosomes (miracidia) for their snail intermediate hosts plays a critical role in parasite transmission. Using field-derived strains of Kenyan snails and parasites, we tested two main hypotheses: (1) Parasites prefer the most compatible host, and (2) parasites avoid hosts that are already infected. We tested preference to three Biomphalaria host snail taxa (B. pfeifferi, B. sudanica, and B. choanomphala), using allopatric and sympatric Schistosoma mansoni isolates and two different nonhost snail species that co-occur with Biomphalaria, Bulinus globosus, and Physa acuta. We also tested whether schistosomes avoid snail hosts that are already infected by another trematode species and whether competitive dominance played a role in their behavior. Preference was assessed using two-way choice chambers and by visually counting parasites that moved toward competing stimuli. In pairwise comparisons, we found that S. mansoni did not always prefer the more compatible snail taxon, but never favored an incompatible host over a compatible host. While parasites preferred B. pfeifferi to the nonhost species B. globosus, they did not significantly prefer B. pfeifferi versus P. acuta, an introduced species in Kenya. Finally, we demonstrated that parasites avoid infected snails if the resident parasite was competitively dominant (Patagifer sp.), and preferred snails infected with subordinates (xiphidiocercariae) to uninfected snails. These results provide evidence of “fine tuning” in the ability of schistosome miracidia to detect hosts; however, they did not always select hosts that would maximize fitness. Appreciating such discriminatory abilities could lead to a better understanding of how ecosystem host and parasite diversity influences disease transmission and could provide novel control mechanisms to improve human health.
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Affiliation(s)
- Martina R. Laidemitt
- Center for Evolutionary and Theoretical Immunology, Department of Biology University of New Mexico Albuquerque New Mexico USA
| | - Alyssa M. Gleichsner
- Department of Biological Sciences State University of New York, College at Plattsburgh Plattsburgh New York USA
| | - Christopher D. Ingram
- College of Osteopathic Medicine of the Pacific Northwest Western University of Health Sciences Lebanon Oregon USA
| | - Steven D. Gay
- College of Osteopathic Medicine of the Pacific Northwest Western University of Health Sciences Lebanon Oregon USA
| | | | - Martin W. Mutuku
- Center for Biotechnology Research and Development Kenya Medical Research Institute (KEMRI) Nairobi Kenya
| | - Polycup Oraro
- Center for Biotechnology Research and Development Kenya Medical Research Institute (KEMRI) Nairobi Kenya
| | - Dennis J. Minchella
- Department of Biological Sciences Purdue University West Lafayette Indiana USA
| | - Gerald M. Mkoji
- Center for Biotechnology Research and Development Kenya Medical Research Institute (KEMRI) Nairobi Kenya
| | - Eric S. Loker
- Center for Evolutionary and Theoretical Immunology, Department of Biology University of New Mexico Albuquerque New Mexico USA
| | - Michelle L. Steinauer
- College of Osteopathic Medicine of the Pacific Northwest Western University of Health Sciences Lebanon Oregon USA
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6
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Platt RN, Le Clec'h W, Chevalier FD, McDew‐White M, LoVerde PT, Ramiro de Assis R, Oliveira G, Kinung'hi S, Djirmay AG, Steinauer ML, Gouvras A, Rabone M, Allan F, Webster BL, Webster JP, Emery AM, Rollinson D, Anderson TJC. Genomic analysis of a parasite invasion: Colonization of the Americas by the blood fluke Schistosoma mansoni. Mol Ecol 2022; 31:2242-2263. [PMID: 35152493 PMCID: PMC9305930 DOI: 10.1111/mec.16395] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 01/25/2022] [Accepted: 01/31/2022] [Indexed: 11/29/2022]
Abstract
Schistosoma mansoni, a snail-borne, blood fluke that infects humans, was introduced into the Americas from Africa during the Trans-Atlantic slave trade. As this parasite shows strong specificity to the snail intermediate host, we expected that adaptation to South American Biomphalaria spp. snails would result in population bottlenecks and strong signatures of selection. We scored 475,081 single nucleotide variants in 143 S. mansoni from the Americas (Brazil, Guadeloupe and Puerto Rico) and Africa (Cameroon, Niger, Senegal, Tanzania, and Uganda), and used these data to ask: (i) Was there a population bottleneck during colonization? (ii) Can we identify signatures of selection associated with colonization? (iii) What were the source populations for colonizing parasites? We found a 2.4- to 2.9-fold reduction in diversity and much slower decay in linkage disequilibrium (LD) in parasites from East to West Africa. However, we observed similar nuclear diversity and LD in West Africa and Brazil, suggesting no strong bottlenecks and limited barriers to colonization. We identified five genome regions showing selection in the Americas, compared with three in West Africa and none in East Africa, which we speculate may reflect adaptation during colonization. Finally, we infer that unsampled populations from central African regions between Benin and Angola, with contributions from Niger, are probably the major source(s) for Brazilian S. mansoni. The absence of a bottleneck suggests that this is a rare case of a serendipitous invasion, where S. mansoni parasites were pre-adapted to the Americas and able to establish with relative ease.
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Affiliation(s)
- Roy N. Platt
- Texas Biomedical Research InstituteSan AntonioTexasUSA
| | | | | | | | | | | | - Guilherme Oliveira
- Centro de Pesquisas René Rachou—Fiocruz/MGBelo HorizonteBrazil
- Instituto Tecnológico ValeBelémBrazil
| | | | - Amadou Garba Djirmay
- Réseau International Schistosomiases Environnemental Aménagement et Lutte (RISEAL)NiameyNiger
| | | | | | | | - Fiona Allan
- Department of Pathobiology and Population SciencesRoyal Veterinary College, Centre for Emerging, Endemic and Exotic DiseasesUniversity of LondonHertfordshireUK
- London Centre for Neglected Tropical Disease Research, Imperial College LondonSchool of Public HealthLondonUK
| | - Bonnie L. Webster
- Natural History MuseumLondonUK
- London Centre for Neglected Tropical Disease Research, Imperial College LondonSchool of Public HealthLondonUK
| | - Joanne P. Webster
- Department of Pathobiology and Population SciencesRoyal Veterinary College, Centre for Emerging, Endemic and Exotic DiseasesUniversity of LondonHertfordshireUK
- London Centre for Neglected Tropical Disease Research, Imperial College LondonSchool of Public HealthLondonUK
| | - Aidan M. Emery
- Natural History MuseumLondonUK
- London Centre for Neglected Tropical Disease Research, Imperial College LondonSchool of Public HealthLondonUK
| | - David Rollinson
- Natural History MuseumLondonUK
- London Centre for Neglected Tropical Disease Research, Imperial College LondonSchool of Public HealthLondonUK
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7
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Trienekens SCM, Faust CL, Besigye F, Pickering L, Tukahebwa EM, Seeley J, Lamberton PHL. Variation in water contact behaviour and risk of Schistosoma mansoni (re)infection among Ugandan school-aged children in an area with persistent high endemicity. Parasit Vectors 2022; 15:15. [PMID: 34991702 PMCID: PMC8734346 DOI: 10.1186/s13071-021-05121-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 12/11/2021] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Annual 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. METHODS Data 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. RESULTS Children 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. CONCLUSIONS Children 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.
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Affiliation(s)
- Suzan C. M. Trienekens
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Institute of Health & Wellbeing, College of Social Sciences, University of Glasgow, Glasgow, UK
| | - Christina L. Faust
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Fred Besigye
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | - Lucy Pickering
- Institute of Health & Wellbeing, College of Social Sciences, University of Glasgow, Glasgow, UK
| | | | - Janet Seeley
- Medical Research Council/Uganda Virus Research Institute, Entebbe, Uganda
- Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK
| | - Poppy H. L. Lamberton
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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