Detection of ascaridoid nematode parasites in the important marine food-fish Conger myriaster (Brevoort) (Anguilliformes: Congridae) from the Zhoushan Fishery, China

Abstract

BackgroundThe whitespotted conger Conger myriaster (Brevoort) (Anguilliformes: Congridae) is an extremely marketable food fish, commonly consumed as sashimi or sushi in some Asian countries (i.e. Japan, Korea and China). Conger myriaster is also suspected as being an extremely important source of human anisakidosis. However, there is currently very little information on the levels of infection with ascaridoid nematode parasites in this economically important marine fish. The aims of the present study are to determine the species composition, prevalence and mean intensity of ascaridoid parasites of C. myriaster caught in the Zhoushan Fishery.ResultsA total of 1142 third-stage ascaridoid larvae were isolated from 204 C. myriaster. The overall prevalence of infection was 100% (mean intensity 5.6). Nine species of such larvae were accurately identified using integrative taxonomic techniques involving both morphological and genetic data; these included Anisakis pegreffii, A. typica and A. simplex (sensu stricto) × A. pegreffii, Hysterothylacium fabri, H. aduncum, H. sinense, H. amoyense, H. zhoushanense and Raphidascaris lophii. Although high levels of infection and species richness were revealed in C. myriaster, most of the ascaridoid parasites (1135 individuals) were collected from the body cavity and visceral organs of the fish and only seven individuals of A. pegreffii were found in the musculature.ConclusionsThis study represents the first report C. myriaster from the Zhoushan Fishery being heavily infected with third-stage ascaridoid larvae. Among the ascaridoid larvae parasitic in this fish, an important etiological agent of human anisakidosis, A. pegreffii (L3), represents the predominant species. The genus Hysterothylacium has the highest species richness, with H. fabri (L3) being the most prevalent species. This high level of infection of A. pegreffii (L3) in C. myriaster suggests a high risk of anisakidosis or associated allergies for people consuming raw or poorly cooked fish originating from this marine area. These findings provide important basic information on the occurrence and infection parameters of ascaridoid nematodes in this economically important marine fish. They also have significant implications for the prevention and control of human anisakidosis when conger eels from the Zhoushan Fishery are consumed.

Anisakis Nematodes in Fish and Shellfish- from infection to allergies

“…This, has been attributed to be likely due to the high frequency of self-limiting characteristic of the infection, missed diagnosis and under-reporting since symptoms of anisakiasis are usually non-specific (EFSA-BIOHAZ, 2010), as well as probable low-level knowledge of seafood parasitology among medical experts (Shamsi and Sheorey, 2018) or low occurrence of Anisakis migration into the musculatures of infected fish. In China, the white-spotted conger ( Conger myriaster ) was recently reported to have a high prevalence of Anisakis pegreffii (Chen et al, 2018). Atlantic cod fish ( Gadus morhua) have been associated with numerous penetrating A. simplex larvae (Levsen and Berland, 2012), while Atlantic salmon (Salmo salar) and sea trout ( Salmo trutta ) returning to rivers in Scotland, England and Wales have also been documented to be infected with a high number of A. simplex larvae (Buchmann and Mehrdana, 2016).…”

“…Storage, after-harvest handling and fish preparation are the focus of preventive measures. Migration of larvae into the muscle might be prevented by immediate evisceration of fish after being caught (Chen et al, 2018). However, since this immediate cleaning may most likely be performed at sea, resulting in removed contaminated viscera being thrown back into the sea and eaten by other fish, the prevalence of infection may be heightened through this practice (McClelland et al, 1990).…”

First molecular characterization of the small subunit ribosomal RNA gene of Hysterothylacium fabri larvae (Nematoda: Raphidascarididae) from Mediterranean Sea

“…No intraspecific nucleotide differences were detected in the sequence analyses of partial rrnS and ITS region. Our H. fabri isolates displayed 98.90-100% identity to that of the ITS sequences of H. fabri (accession from JX974558, MH211474-94, MF539787-89, JQ520158, KU948632-37, KC852206) recorded previously from the Mediterranean Sea, South Korean waters, and Chinese waters (Chen et al 2018;Pekmezci et al 2014;Tedesco et al 2018;Zhang et al 2018). Moreover, our H. fabri isolates (MK886659) showed 96.42% identity with H. fabri from China (MF140349) based on rrnS gene.…”

Occurrence and molecular characterization of zoonotic Anisakis simplex sensu stricto and Anisakis pegreffii larvae in retail‐marketed fish

“…They showed a 99% identity with A. pegreffii GB isolate (JN968593) collected from Atlantic herring, Denmark (Kuhn, García‐Màrquez, & Klimpel, ). Moreover, they had 99% identity with A. pegreffii GB isolates (MF539767, MF539764) from marine fish Conger myriaster (Brevoort), China (Chen et al, ).…”