The Occurrence of Freshwater Fish-Borne Zoonotic Helminths in Italy and Neighbouring Countries: A Systematic Review

In recent years, the consumption of fish products has surged in European countries, being an essential part of a healthy diet. Despite representing a small part of EU production, freshwater fisheries hold considerable significance for lake-dwelling populations and tourists seeking traditional dishes. This increased fish consumption has brought to light potential health risks associated with fish-borne zoonotic helminths (FBZHs), now acknowledged as global food-borne parasites. Fish-borne zoonotic helminths belong to various taxonomic groups, including nematodes (Anisakidae), trematodes (Opisthorchiidae and Heterophyidae), and cestodes (Diphyllobothriidae). More than 50 species of FBZH are known to cause human infections, derived from eating raw or undercooked aquatic foods containing viable parasites. Despite increased attention, FBZHs remain relatively neglected compared to other food-borne pathogens due to factors like chronic disease progression and under-diagnosis. This systematic review concentrates on the prevalence of six freshwater FBZHs (Clinostomum complanatum, Contracaecum rudolphii, Dibothriocephalus latus, Eustrongylides excisus, Opisthorchis felineus, and Pseudamphistomum truncatum) in Italy and neighbouring countries. The study explores the expansion of these parasites, analysing their biological and epidemiological aspects, and the factors that influence their proliferation, such as the increased cormorant population and the lake eutrophication phenomena. In summary, this research highlights the necessity for further research, the development of spatial databases, and the establishment of a unified European policy to effectively manage these multifaceted health concerns. It strongly advocates adopting a One-Health approach to address the growing incidence of parasitic zoonoses within the context of food safety in EU countries.

Genetic characterization of Dibothriocephalus latus and Dibothriocephalus dendriticus (Cestoda: Diphyllobothriidae) from Chile based on haplotype analysis using mitochondrial DNA markers

Dibothriocephalus latus and Dibothriocephalus dendriticus are found throughout the temperate and sub-arctic zones of the northern hemisphere, but they are also found in the southern core countries of South America, Chile and Argentina. Genetic characteristics of D. latus and D. dendriticus from South America have yet to be fully defined. The present study aimed to understand the genetic characteristics of D. latus and D. dendriticus from Chile by haplotype network analysis of mitochondrial cytochrome c oxidase subunit I gene (cox1) and cytochrome b gene (cob), as well as their origins. Dibothriocephalus latus and D. dendriticus plerocercoid larvae were obtained from feral and/or wild salmonids captured in Lake Llanquihue in Región de Los Lagos, and Lake Panguipulli in Región de Los Ríos, located south of central Chile. Haplotype analysis of D. latus revealed that H1 in cox1 and H2 in cob are the key haplotypes common to D. latus across the world, including Chile, and both genes exhibited limited genetic diversity in D. latus. It was assumed that D. latus was brought into South America by European and Russian immigrants in the 19th century as previously reported. In contrast, both the cox1 and cob of D. dendriticus display considerable genetic diversity, with no common haplotypes between D. dendriticus populations from Chile and the northern hemisphere. More intriguingly, two cob haplotypes (H24, H25) detected in Chilean D. dendriticus were closely linked to haplotypes (H30,H31) detected in North American D. dendriticus, strongly implying that D. dendriticus in Chile was brought by piscivorous migrating birds from North America. It has also been estimated that the D. dendriticus from Chile genetically diverged from the D. dendriticus from the northern hemisphere approximately 1.11 million years ago, long before humans migrated to the southern parts of South America.

[New eating habits, new parasitic risks: The example of fish]

Introduction

In the past decades, the massive explosion of "Japanese" restaurants serving raw fish popularised new culinary habits in France. At the same time, consumers have made a habit of preparing raw or pickled fish dishes themselves at home. As a result, the identification of live parasitic worm larvae in raw fish flesh is common and a source of concern for professionals or amateur cooks. Sometimes, these worms are spit out or removed after fibroscopy in patients developing severe epigastric pain quickly after eating raw fish. This paper is aiming at having a quick review of the main parasites transmitted to humans by eating raw fish in France.

Methods

This article is based on the personal experience of the authors, on references preferentially from the French literature and on the results of the Fish Parasites (ANR) research program.

Results

From 2011 to 2014, Fish-Parasites (ANR) assessed the prevalence of parasitism in sea and freshwater fish belonging to 29 species. About 57% of sea fish were parasitised by Anisakidae. Larvae of Dibothriocephalus latus were found in pike, perch, and burbot in Lake Geneva but in none of the fish examined from Annecy or Le Bourget lakes. Concerning human anisakidosis, a retrospective survey was carried out in the years 2010 to 2014 among all medical parasitology laboratories from university hospitals in France. Thirty-seven cases of anisakidosis have been reported, including 18 cases of allergic anisakidosis. Six additional cases of severe Anisakidae allergy were reported to the National Allergovigilance Network over the same period.

Conclusions

Despite the increase in consumption of raw fish, and compared to previous studies, cases of anisakidosis are decreasing, but their allergenic potential is increasing. The incidence of dibothriocephalosis, after some trend of emergence on the shores of Lake Geneva some 20 years ago, is currently decreasing, but sporadic cases of importation are still reported. Actions with professionals (investigation, providing of information) and research programs on management of parasitic risk control are being pursued and have resulted in an update of the technical instruction of the French General Directorate for Food on the control of parasitic risk in fish.

Host Switching of Zoonotic Broad Fish Tapeworm (Dibothriocephalus latus) to Salmonids, Patagonia

Diphyllobothriosis is a reemerging zoonotic disease because of global trade and increased popularity of eating raw fish. We present molecular evidence of host switching of a human-infecting broad fish tapeworm, Dibothriocephalus latus, and use of salmonids as intermediate or paratenic hosts and thus a source of human infection in South America.