Hybrid Swarm: the role of hybridization in the invasive capacity, epidemiology and diagnostic of schistosomiasis – HySWARM

There is an increasing interest on the effect of global changes on the transmission of infectious diseases. Both environmental and anthropogenic changes are expected to promote outbreaks and spread of pathogens. In particular, tropical infectious diseases are expected to move towards more temperate latitudes. Until 2013, urogenital Schistosomiasis was restricted to tropical and sub-tropical areas. In summer 2013, a schistosomiasis outbreak has emerged in Corsica with more than 100 cases. Corsica is a French Mediterranean island, which is very popular for tourists from throughout Europe due to the natural beauty of the environment. In summer 2015 and 2016, the contamination has resumed and schistosomiasis has been classified in the list of French notifiable infectious disease, making this parasitosis a "not only" tropical disease. Genomic analysis shows that the parasite incriminated is not the pure usual parasite involved in human urogenital schistosomiasis (Schistosoma haematobium), but rather an hybrid between the latter and a parasite infecting animals (S. bovis). The hybrid status of the parasite makes the epidemiological situation much more complex by increasing the risk of (i) higher compatibility/virulence for both invertebrate and vertebrate hosts (i.e. hybrid vigor) (ii) widening the host spectrum and the zoonotic transmission consequences (iii) selecting for drug tolerant parasites (iv) impairing the diagnosis efficiency.
HySWARM project is based on an experimental evolution protocol that consists in creating hybrid parasite lines with controlled genetic background. For this purpose, we will first cross the two pure species using reciprocal crosses then we will apply two successive inbreeding backcrosses with either S. bovis or S. haematobium pure species. According to the parasite introgression level from either the human or the animal parasite forms we propose to subsequently analyze (i) the parasite hybrid vigor in the European environmental context (ii) the tolerance of the parasite to the unique treatment used to fight schistosomiasis (praziquantel) (iii) the ability of the parasite to wider its host spectrum (both mollusc and vertebrate) (iv) to analyze the molecular determinants of the host/parasite virulence using a dual approach (RNAseq and DNAseq) (v) to improve diagnosis efficiency by parasitological stool examination (feces and urine), DNA or antigen detection (vi) to reinstate the results obtained from the laboratory to the real ecological situation in the field. In agreement with the One Health concept, our project will bring together experts in the fields of evolutionary biology and ecology, omics data analyses, eco-epidemiology, veterinary science and medicine. Together they will deliver a project working towards the ultimate goal of adequate risk assessment and effective control strategies for disease transmission in a changing world.