Anisakid and Raphidascaridid parasites in Trachurus trachurus: infection drivers and possible effects on the host\u2019s condition

Fabio Macchioni,Perla Tedesco,Monica Caffara,Alessandro Ligas,Francesca Cecchi,Paolo Sartor,Gianfranca Monni,Carlo Pretti,Andrea Massaro,Vanessa Cocca

doi:10.1007/s00436-021-07200-0

Abstract

This study investigated the distribution of nematode larvae of Anisakidae and Raphidascarididae (genera Anisakis and Hysterothylacium) in Trachurus trachurus (Linnaeus, 1758) in the Ligurian and central-northern Tyrrhenian Seas. The relationship between the number of parasites and the length and weight parameters of the fish was assessed, and the possible effect of the parasites on the condition factor was evaluated. A total of 190 T. trachurus specimens were collected in July 2019. Parasites were found in 70 individuals. A total of 161 visible larvae were collected in the viscera. Morphological analysis revealed the presence of Anisakis spp. in 55 fish and Hysterothylacium spp. in 15 fish, while 5 fish showed coinfection with both genera. The specimens subjected to PCR (n = 67) showed that 85% of the Anisakis larvae analyzed belonged to the species A. pegreffii, while the remaining 15% belonged to hybrids of A. pegreffii-A. simplex (s.s.). A total of 58% (n = 7) of the Hysterothylacium larvae analyzed belonged to the species H. fabri, while 42% belonged to the species H. aduncum. Our results support the hypothesis that infection with these parasites does not affect the condition of the fish host analyzed, and that body size and depth are major drivers in determining infection levels with Anisakid and Raphidascaridid nematodes.

Highlights

Anisakidosis is a fish-borne zoonosis following ingestion of the third larval stage of nematodes of the family Anisakidae
A total of 190 specimens of T. trachurus were collected during the MEDITS survey in July 2019, of which 107 were female and 83 were male
The present study provides information on the distribution of third-stage larvae of A pegreffii, H. aduncum, and H. fabri in T. trachurus from the Ligurian and Tyrrhenian Seas, correlating the infection data with the biological and biometric features of the hosts

Summary

Introduction

Species of the genus Hysterothylacium Ward and Magath, 1917, formerly belonging to the Anisakidae and currently assigned to the family Raphidascarididae, are common parasites in different marine and freshwater fish species (Bezerra et al 2020). Evidence of the direct consequences of Hysterothylacium infection on fish health is limited: parasites of this genus are considered only mildly pathogenic for adult fish (Ishikura et al 1993; Yagi et al 1996; Valero et al 2003; Cavallero et al 2012); mortality episodes in larval and juvenile fish have been reported. Generally not listed among fish-borne zoonotic agents, preliminary evidence on the allergenic potential of Hysterothylacium species (Fernández-Caldas et al 1998; Valero et al 2003) suggests their importance in relation to food safety and human health

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Conclusion