Optimization of tools for the detection and identification of Cryptocotyle metacercariae in fish: Digestion method and viability studies

Abstract

Digenean trematodes are parasitic worms that have a complex life cycle with several successive hosts. In most cases, molluscs act as the first intermediate host and fish as the second intermediate host, whereafter marine birds complete the life cycle upon eating parasitized fish. Adult digeneans develop into the adult stage in the avian gastrointestinal tract; eggs are released with host faeces and are ingested by the first intermediate host in which sporocysts and rediae develop, subsequently releasing free-swimming cercariae that go on to infect fish. Following penetration, the parasites encyst and evolve to the metacercarial stage protected by a proteinaceous cyst wall.The family Heterophyidae comprises 13 genera with zoonotic potential (Acanthotrema,

Re‐evaluation of certain aspects of the EFSA Scientific Opinion of April 2010 on risk assessment of parasites in fishery products, based on new scientific data. Part 1: ToRs1–3

“…Multiplex PCR (rDNA 18S locus and mtDNA cytb locus) has also been developed for the identification of C. formosanus in fish (Jaruboonyakorn et al, 2022). Molecular tools for the identification of opisthorchioidea in general have been reviewed by Duflot et al (2021).…”

“…The method is also used for the extraction of trematodes (metacercariae) and cestodes (plerocercoids) from large quantities of fish (Borges et al., 2015 ; EFSA BIOHAZ Panel, 2010 ). Recently, four artificial digestion protocols have been compared for the detection of Cryptocotyle metacercariae in fish fillets, suggesting that the orbital digestion was the least destructive for metacercariae, allowing their better quantification and a reliable morphological identification up to 8 days post‐mortem (Duflot et al., 2021 ). Due to considerable size differences between parasite types (trematode metacercaria ~ of < 1 mm, cestodes between 1 and 30 mm and anisakid larvae between 1 and 45 mm), appropriate filter sizes should be selected.…”

“…Molecular tools for the identification of opisthorchioidea in general have been reviewed by Duflot et al. ( 2021 ).…”

Black spot diseases in seven commercial fish species from the English Channel and the North Sea: infestation levels, identification and population genetics of Cryptocotyle spp.

“…Their swimming cercariae encyst, develop into the metacercarial stage, and cause immune cutaneous black spot. Black spot disease is an immune response towards encysted metacercariae, due to the concentration of melanomacrophages at the infection site [21,78]. These black spots may induce esthetic problems that lower the commercial value of the fish [44].…”

Morphological and molecular identification of Cryptocotyle lingua metacercariae isolated from Atlantic cod (Gadus morhua) from Danish seas and whiting (Merlangius merlangus) from the English Channel

“…Cryptocotyle delamurei Jurachno 1987 was first described in the northern fur seal. Cryptocotyle lingua Creplin 1825 has Littorina littorea as the first intermediate host (Blakeslee et al 2008;Landis et al 2012), a variety of marine fish as second intermediate host such as gobies, gadoids, clupeids (Borges et al 2015;Duflot, et al 2021a;Goncharov et al 2017) and piscivorous birds as final host (Linton 1915;Stunkard 1942). The first intermediate host of Cryptocotyle Section Editor: Matthew Thomas Wayland.…”