Caractérisation et distribution de Cryptocotyle, parasites des produits de la pêche, en Manche - mer du Nord.

Parasite of the genus Cryptocotyle are potential zoonotic trematodes present worldwide in many fish species. So far, its impact on human health is still unknown. Moreover, few publications deal with its recovery, identification and distribution among commercially important fish. Tool development was carried out for quantification of Cryptocotyle infection, isolation, including optimization of digestion, assessment of viability of metacercariae post mortem, and identification of parasite. Then, an epidemiological study was performed on seven commercial fish species: herring (Clupea harengus), sprat (Sprattus sprattus), whiting (Merlangius merlangus), pout (Trisopterus luscus), dab (Limanda limanda), flounder (Platichthys flesus) and plaice (Pleuronectes platessa). The samples were collected during the sea campaign of the International Bottom Trawl Survey in the Eastern English Channel and the North Sea in January 2019 and 2020. Cryptocotyle infection was estimated by counting black spots due to this parasite on the whole fish. Metacercariae were characterized by classical methods from a morphological point of view with microscopic observations and from a molecular perspective with Sanger sequencing of fragments of mtDNA cox1 gene and of rDNA ITS region. Morphological data were compared to available literature data. Phylogenetic trees including reference sequences were built to confirm morphological and molecular identifications. The prevalence, intensity and abundancy displayed differences between fish species and fishing areas. This survey constitutes the first description of C. lingua and C. concava metacercariae in the Eastern English Channel and North Sea ecosystems. [ABSTRACT FROM AUTHOR]