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Transmission dynamics and hybridization of human and animal trematodes in sub-Saharan Africa

English title Transmission dynamics and hybridization of human and animal trematodes in sub-Saharan Africa
Applicant Utzinger Jürg
Number 170113
Funding scheme Project funding (Div. I-III)
Research institution Abt. öff. Gesundheitswesen und Epidemiologie Schweizerisches Tropen- und Public Health-Institut
Institution of higher education University of Basel - BS
Main discipline Methods of Epidemiology and Preventive Medicine
Start/End 01.01.2017 - 31.10.2020
Approved amount 502'783.00
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All Disciplines (6)

Discipline
Methods of Epidemiology and Preventive Medicine
Medical Statistics
Veterinary Medicine
Infectious Diseases
Human Ecology
Tropical Medicine

Keywords (15)

One health; Parasitology; Social-ecological systems; Geographical information system; Phylogeography; Cattle; Epidemiology; Risk profiling; Schistosoma spp.; Land use; Transdisciplinarity; Human; Hydrology; Population genetics; Fasciola spp.

Lay Summary (German)

Lead
Übertragungsdynamik und Hybridisierung von menschlichen und tierischen Trematodenarten in Westafrika
Lay summary

Schistosoma- und Fasciola-Arten sind parasitische Würmer ("Trematoden"), die Menschen und Tiere befallen und erhebliche wirtschaftliche Verluste verursachen. in der Elfenbeinküste kommen je mehrere Arten vor, ihre Unterscheidung ist mit Standardmethoden jedoch unzuverlässig. Das gleichzeitige Vorkommen mehrerer Trematodenarten ermöglicht zudem das Entstehen von Hybridarten, was die Übertragungsdynamik der Parasiten verändern kann und Gültigkeit und Effizienz bestehender diagnostischer Ansätze und Kontrollstrategien in Frage stellt.

Ziel dieses Projektes ist ein tieferes Verständnis der Übertragungsdynamik von Trematoden und der Rolle von Hybriden in Westafrika. Insbesondere soll beantwortet werden: (1) Welche Trematodenarten kommen in der Elfenbeinküste vor? (2) Wie häufig sind Hybriden und wie unterscheiden sie sich von ihren Elternarten? (3) Unterscheiden sich die Parasitenpopulationen verschiedener Wirtsarten (Mensch, Rind, Schaf, Ziege, Schnecke)? (4) Beeinflusst die jährliche grenzüberschreitende Wanderung von Nomaden und ihren Herden die lokale Parasitendynamik und die Häufigkeit von Hybriden? (5) Wie stark ist der Infektionsdruck mit Fasciola bei Rindern nach der Behandlung mit Triclabendazol, dem besten vorhandenen Medikament?

Das Projekt wird die Identität von Trematoden in der Elfenbeinküste klären und aufzeigen, ob Wanderherden lokale Trematodenpopulationen verändern und Zonen mit erhöhter Gefahr für die Entstehung neuartiger Parasiten und Krankheiten definieren. Die Ergebnisse werden klären, ob in der Elfenbeinküste Hybridisierung das Wirtsspektrum von Trematoden ändert, und ob die aktuellen Diagnose- und Kontrollansätze angebracht sind. Die entwickelten molekularen Methoden und die Ausbildung von afrikanischen Studenten wird zum Aufbau dringend benötigter Forschungs- und Interventionskapazitäten in Westafrika beitragen.

Direct link to Lay Summary Last update: 01.10.2016

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
123185 Morbidity patterns and transmission dynamics of neglected tropical diseases in semi-arid and humid Africa 01.11.2008 ProDoc
141246 Systems epidemiology of human schistosomiasis and livestock fascioliasis in sub-Saharan Africa 01.08.2012 Project funding (Div. I-III)
183577 African contributions to global health: Circulating knowledge and innovations 01.06.2019 Sinergia

Abstract

Schistosoma and Fasciola species are trematode parasites that are of considerable public health importance and cause significant livestock disease and economic losses. In a recently completed project funded by the Swiss National Science Foundation, we demonstrated the presence of Schistosoma haematobium in humans and Schistosoma bovis and Fasciola gigantica in different livestock species in Côte d’Ivoire and Chad. We further showed that infection patterns in humans and livestock are intimately linked, and governed by ethnicity and life-styles. However, species distinction using standard diagnostic methods is unreliable, so there is still uncertainty about the exact species present. The co-location of multiple human and animal trematodes in the same geographical areas suggests the possibility of hybrid species. Indeed, this phenomenon has been observed for both Schistosoma and Fasciola; yet, it remains to be investigated for Côte d’Ivoire and Chad. Hybridization has been demonstrated to modify parasite characteristics including host ranges. Hybridization may thus alter transmission dynamics and challenges the validity and efficiency of existing diagnostic approaches and control strategies. The appearance of hybrids between human and animal-infective species in both Schistosoma and Fasciola, as well as their largely overlapping ecologies, call for investigating these two genera and the diseases they cause together using a One Health approach.The goal of this project is to gain a deeper understanding of trematode transmission dynamics and the role of hybrids in sub-Saharan Africa. We address this goal by pursuing five research questions. First, which Schistosoma and Fasciola species are present in Côte d’Ivoire? Second, what is the frequency of different hybrids and does their distribution or other parameters differ from those of the parent species? Third, how are the parasite populations differentiated or linked between different host species (humans, cattle, sheep, goats and snails) and are there host-specific genotypes? Fourth, how does transhumance (i.e. the annual cross-border migration of mobile pastoralists with their herds from Mali) affect parasite dynamics and hybridization in Côte d’Ivoire? Fifth, how strong is re-infection pressure after treatment of cattle with triclabendazole, the current treatment of choice against Fasciola infection?We will generate complete mitochondrial genomes and partial whole-genome sequences of multiple local genotypes to optimize the available molecular methods for West African trematode genotypes. We will employ molecular methods to identify species and hybrids. Population genetic analyses of circulating genotypes in each host species will complement epidemiological studies. Schistosoma bovis will be investigated in greater detail because its hybridization appears to be common and thus may generate human-infective parasites with a livestock reservoir. Cohorts of Fasciola-infected cattle will be treated with triclabendazole and their reinfection status followed over time to investigate infection pressures. Finally, data from the current and the preceding project will contribute to a deterministic model of trematode transmission.The proposed research will quantify trematode diversity and transmission and clarify whether transhumance affects local trematode population dynamics indicating zones of increased risk for emergence of new parasites and zoonotic disease. The results will elucidate to what extent hybridization changes parasite host ranges and transmission, and the validity of current diagnosis and control approaches. The model of trematode transmission will allow us to investigate the effectiveness of competing control strategies for reducing human disease burden and improving livestock production. The locally adapted molecular methods and the training of African students and technicians will contribute to capacity building in partner institutions in sub-Saharan Africa.
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