[Oesophageal localization: a rare complication of anisakidosis due to Pseudoterranova]

Seals, fish, humans and parasites in the Baltic: ecology, evolution and history

Evolutionary and ecological processes affecting the interactions between hosts and parasites in the aquatic environment are at display in the Baltic Sea, a young and ecologically unstable marine ecosystem, where fluctuating abiotic and biotic factors affect the parasitofauna in fish. The dynamic infections of Baltic cod, a subpopulation of the Atlantic cod (Gadus morhua Linnaeus), with third stage anisakid nematode larvae of Pseudoterranova decipiens (Krabbe, 1878) and Contracaecum osculatum (Rudolphi, 1802) have increased following a significant increase of the Baltic grey seal Halichoerus grypus (Fabricius) population in the region. Cod serves as a paratenic host and marine mammals, pinnipeds, are definitive hosts releasing parasite eggs, with faeces, to the marine environment, where embryonation and hatching of the third stage larva take place. The parasite has no obligate intermediate hosts, but various invertebrates, smaller fish and cod act as paratenic hosts transmitting the infection to the seal. Contracaecum osculatum has an impact on the physiological performance of the cod, which optimises transmission of the larva from fish to seal. Thus, a muscle mass decrease of nearly 50% may result from heavy C. osculatum infections, probably amplified by a restricted food availability. The muscle atrophy is likely to reduce the escape reactions of the fish when meeting a foraging seal. In certain regions, where fish and seals are restricted in their migration patterns, such as the semi-enclosed Baltic Sea, the predation may contribute to a severe cod stock depletion. The parasites are zoonotic and represent a human health risk, when consumers ingest insufficiently heat- or freeze-treated infected products. Marked infections of the cod were previously reported during periods with elevated seal populations (late 19th and middle 20th century) and various scenarios for management of risk factors are evaluated in an evolutionary context.

[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.

Nasal localization of a Pseudoterranova decipiens larva in a Danish patient with suspected allergic rhinitis

Pseudoterranoviasis is a zoonotic disease caused by nematode larvae of species within the genus Pseudoterranova (seal worm, cod worm). Most infections are gastrointestinal, oesophageal or pharyngeal, but here we report a nasal infection. A 33-year-old patient suffering from rhinitis for 1.5 years recovered a worm larva from the nose. Diagnosis was performed by morphological and molecular characterization, showing the causative agent to be a third-stage larva of Pseudoterranova decipiens (sensu stricto). Various infection routes are discussed.

A national retrospective survey of anisakidosis in France (2010-2014): decreasing incidence, female predominance, and emerging allergic potential

A retrospective survey was carried out over the years 2010–2014 among all Parasitology laboratories of University hospitals in France (ANOFEL network). The objective was to estimate the incidence of anisakidosis in France as new culinary habits such as the consumption of raw fish (sushi) or undercooked fish are increasing. A total of 37 cases of anisakidosis were notified by all French laboratories: 7 proven cases with evidence of a worm, 12 possible cases with abdominal pain after consumption of raw fish with detection of anti-Anisakis precipitins, and 18 allergic cases defined as acute manifestations after consumption of fish, associated with specific IgE for Anisakis. The median age of affected individuals was 42 years (11-69) and there was a significant predominance of women (67%). Compared with previous surveys in France, this study indicates a decrease in clinical cases of anisakidosis and illustrates the emerging allergic potential of anisakids.

Molecular diagnosis of Pseudoterranova decipiens s.s in human, France

Background

Anisakis and Pseudoterranova are the main genera involved in human infections caused by nematodes of the Anisakidae family. Species identification is complicated due to the lack of differential morphological characteristics at the larval stage, thus requiring molecular differentiation. Pseudoterranova larvae ingested through raw fish are spontaneously eliminated in most cases, but mechanical removal by means of endoscopy might be required. To date, only very few cases of Pseudoterranova infection have been reported in France.

Case presentation

A 19-year-old woman from Northeastern France detected, while brushing her teeth, a larva exiting through her mouth. The patient who presented with headache, diarrhea, and abdominal cramps reported having eaten baked cod. The worm was a fourth-stage larva with a size of 22 × 0.9 mm, and molecular biology identified it as Pseudoterranova decipiens sensu stricto (s. s.). In a second P. decipiens infection case, occurring a few months later, a worm exited through the patient’s nose after she had eaten raw sea bream.

Conclusion

These two cases demonstrate that Pseudoterranova infection is not uncommon among French patients. Therefore, molecular techniques should be more widely applied for a better characterization of anisakidosis epidemiology in France.

First case report of invasive pseudoterranoviasis in Italy

Members of the genera Anisakis and Pseudoterranova are the main causative agents of human anisakidosis: the disease is worldwide distributed, with major impact in countries with a large consumption of raw fish. Because of unspecific symptoms and limited diagnostic tools, incidence and burden of disease are probably underestimated. In Italy, all human infestations where the etiological agent has been properly identified, have been associated to the parasitic species Anisakis pegreffii, the most frequent anisakid in the Mediterranean area. Here, an invasive human case of pseudoterranoviasis is described for the first time in Italy: in 2015, a woman was found infected during a colonoscopy scheduled after the occurrence of nonspecific clinical symptoms. The nematode was found penetrating the ascending colon. The identification was performed by sequencing the mitochondrial region cox2 and by comparison to GenBank retrieved material using the BLAST search tool. The sample showed a 99% identity with Pseudoterranova decipiens sensu stricto. The record underlines the potential risk due to the consumption of raw or undercooked imported fishes.

A case report of Anisakis pegreffii (Nematoda, Anisakidae) identified from archival paraffin sections of a Croatian patient

BACKGROUND

This is the first report of anisakiasis in a Croatian patient, evidenced from an archival paraffin-embedded and hematoxylin-eosin stained tissue section. Anisakiasis has been only suspected in the country based on previously detected anti-Anisakis IgE seroprevalence in the healthy coastal population, as well as an acute case where pathohistological and serological findings suggested the diseases, but the migrating larva has not been retrieved.

CASE PRESENTATION

Seventy years-old female, operated in 1998 for pulmonary carcinoma, was admitted to the General hospital Šibenik, Croatia in 2003, because of gastric pain and nausea that lasted for couple of days. She was showing good general condition, full mobility and lucidity, subfebrile status. Abdominal palpation inferred acute pain in paraumbilical and ileocecal region. Exploratory right pararectal laparotomy revealed a hardened, 5 cm-long structure, located intraluminally in the sigmoid colon, not perforating colon serosa. The process has been dissected and sent for patohistological diagnosis. Results showed a 2 mm-long whitish nematode spiralised in muscular layer of colon mucosa surrounded by granulomatous inflammation.

CONCLUSION

After genomic DNA isolation of the nematode from the histological section, and amplification at the mitochondrial cytochrome oxidase 2 locus, etiological agent has been identified as Anisakis pegreffii. Used methodology suggests that screening of archival suspicious sections is feasible in order to study epidemiology of this zoonotic disease poorly recognised in Croatia.