Morphological and genomic characterisation of the Schistosoma hybrid infecting humans in Europe reveals admixture between Schistosoma haematobium and Schistosoma bovis

• Published in: PLoS neglected tropical diseases Vol. 15; no. 12; p. e0010062
• Main Authors: Kincaid-Smith, Julien, Tracey, Alan, de Carvalho Augusto, Ronaldo, Bulla, Ingo, Holroyd, Nancy, Rognon, Anne, Rey, Olivier, Chaparro, Cristian, Oleaga, Ana, Mas-Coma, Santiago, Allienne, Jean-François, Grunau, Christoph, Berriman, Matthew, Boissier, Jérôme, Toulza, Eve
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.12.2021; Public Library of Science (PLoS)
• Subjects: Animals; Annotations; Assembly; Biodiversity; Biology and Life Sciences; Body Size; Bulinus - parasitology; Causes of; Chimera - anatomy & histology; Chimera - genetics; Chimera - growth & development; Compatibility; Disease Vectors; Earth Sciences; Economic impact; Economics; Eggs; Epidemiology; Europe; Female; Females; Fertility; Genetic analysis; Genetic aspects; Genetic markers; Genetic screening; Genetics; Genome, Helminth; Genomes; Genomics; Human diseases; Humans; Hybrid animals; Hybridization; Hybridization, Genetic; Hybrids; Identification and classification; Introduced species; Introgression; Laboratories; Life cycle; Life cycles; Life Sciences; Livestock; Malaria; Male; Males; Medicine and Health Sciences; Microbiology and Parasitology; Morphology; Morphometry; Offspring; Parameters; Parasites; Parasitic diseases; Parasitology; Parasitoses; Populations and Evolution; Public health; Schistosoma; Schistosoma - anatomy & histology; Schistosoma - genetics; Schistosoma - growth & development; Schistosoma bovis; Schistosoma haematobium; Schistosoma haematobium - anatomy & histology; Schistosoma haematobium - genetics; Schistosoma haematobium - growth & development; Schistosomiasis; Schistosomiasis - parasitology; Snails - parasitology; Standard deviation; Strains; Tropical diseases; Tropical environments; Vector-borne diseases; Vectors; Worms; Europe; Africa
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0010062

Schistosomes cause schistosomiasis, the world's second most important parasitic disease after malaria in terms of public health and social-economic impacts. A peculiar feature of these dioecious parasites is their ability to produce viable and fertile hybrid offspring. Originally only present in the tropics, schistosomiasis is now also endemic in southern Europe. Based on the analysis of two genetic markers the European schistosomes had previously been identified as hybrids between the livestock- and the human-infective species Schistosoma bovis and Schistosoma haematobium, respectively. Here, using PacBio long-read sequencing technology we performed genome assembly improvement and annotation of S. bovis, one of the parental species for which no satisfactory genome assembly was available. We then describe the whole genome introgression levels of the hybrid schistosomes, their morphometric parameters (eggs and adult worms) and their compatibility with two European snail strains used as vectors (Bulinus truncatus and Planorbarius metidjensis). Schistosome-snail compatibility is a key parameter for the parasites life cycle progression, and thus the capability of the parasite to establish in a given area. Our results show that this Schistosoma hybrid is strongly introgressed genetically, composed of 77% S. haematobium and 23% S. bovis origin. This genomic admixture suggests an ancient hybridization event and subsequent backcrosses with the human-specific species, S. haematobium, before its introduction in Corsica. We also show that egg morphology (commonly used as a species diagnostic) does not allow for accurate hybrid identification while genetic tests do.