How effective is freezing at killing Anisakis simplex, Pseudoterranova krabbei, and P. decipiens larvae? An experimental evaluation of time-temperature conditions

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

Surveillance data published since 2010, although limited, showed that there is no evidence of zoonotic parasite infection in market quality Atlantic salmon, marine rainbow trout, gilthead seabream, turbot, meagre, Atlantic halibut, common carp and European catfish. No studies were found for greater amberjack, brown trout, African catfish, European eel and pikeperch. Anisakis pegreffii, A. simplex (s. s.) and Cryptocotyle lingua were found in European seabass, Atlantic bluefin tuna and/or cod, and Pseudamphistomum truncatum and Paracoenogonimus ovatus in tench, produced in open offshore cages or flow-through ponds or tanks. It is almost certain that fish produced in closed recirculating aquaculture systems (RAS) or flow-through facilities with filtered water intake and exclusively fed heat-treated feed are free of zoonotic parasites. Since the last EFSA opinion, the UV-press and artificial digestion methods have been developed into ISO standards to detect parasites in fish, while new UV-scanning, optical, molecular and OMICs technologies and methodologies have been developed for the detection, visualisation, isolation and/or identification of zoonotic parasites in fish. Freezing and heating continue to be the most efficient methods to kill parasites in fishery products. High-pressure processing may be suitable for some specific products. Pulsed electric field is a promising technology although further development is needed. Ultrasound treatments were not effective. Traditional dry salting of anchovies successfully inactivated Anisakis. Studies on other traditional processes - air-drying and double salting (brine salting plus dry salting) - suggest that anisakids are successfully inactivated, but more data covering these and other parasites in more fish species and products is required to determine if these processes are always effective. Marinade combinations with anchovies have not effectively inactivated anisakids. Natural products, essential oils and plant extracts, may kill parasites but safety and organoleptic data are lacking. Advanced processing techniques for intelligent gutting and trimming are being developed to remove parasites from fish.

Recent developments in the use of cold plasma, high hydrostatic pressure, and pulsed electric fields on microorganisms and viruses in seafood

Non-thermal processing methods, such as cold plasma (CP), high pressure processing (HPP) and pulsed electric fields (PEF), have been proposed for natural and fresh-like foods to inactivate microorganisms at nearly-ambient or moderate temperature. Since natural, safe, and healthy foods with longer shelf-life are increasingly demanded, these requests are challenging to fulfill by using current thermal processing technologies. Thus, novel preservation technologies based on non-thermal processing methods are required. The aim of this article is to provide recent developments in maintaining seafood safety via CP, HHP, and PEF technologies, as well as their mechanisms of action regarding contamination with food-borne microorganisms. Their application to control parasites, spores and the possibility to eradicate the hazard of SARS-CoV-2 transmission through seafood products are also discussed. CP, HHP, and PEF have been applied to inactivate food-borne microorganisms in the seafood industry. However, the drawbacks for each emerging technology have also been reported. To ensure safety and maintain quality of seafood products, the combination of these processing techniques with natural antimicrobial agents or existing thermal methods may be more applicable in the case of the seafood industry. Further studies are required to examine the effects of these methods on viruses, parasites, and SARS-CoV-2 in seafood.

Potential hazards associated with the consumption of Scombridae fish: Infection and toxicity from raw material and processing

Scombridae fish (tuna, bonito, and mackerel) have significant ecological and economic values. They are very appreciated by consumers worldwide for their high-quality flesh and for their high nutritional value. However, consumption of Scombridae fish is potentially hazardous. Indeed, several cases of infections and toxicity linked to the consumption of Scombridae fish as raw, or processed food products have been reported worldwide. In this review, we presented the most common health risks associated with Scombridae fish consumption. Diseases associated with the consumption of these fish are generally infectious or toxic and are caused by biological hazards such as bacteria, viruses, parasites, or chemicals hazards that enter the body through contaminated fish (Polycyclic Aromatic Hydrocarbons, histamine) or by physical contaminants such as heavy metals. The risks of contamination exist throughout the food chain, from primary production to the preparation of products for consumption.

Anisakis simplex (s.l.) resistance to the action of gastric enzymes depends upon previous treatments applied to infected fish mince and affects antigen release

BACKGROUND

Freezing is considered the most suitable technological treatment to avoid Anisakis infection from eating raw or undercooked fish but modifications of their cuticles upon freezing may reduce their resistance to gastric fluids, provoking a greater release of allergens. This work aimed to study the relationship between freezing-induced modifications of Anisakis simplex s.l., antigen recognition, and resistance to oral and gastric digestion in spiked fish mince.

RESULTS

(i) Differences between non-treated larvae and larvae that survived freezing / thawing were studied in terms of respiratory capacity, survival in simulated gastric fluid (SGF), recognition of antigens and allergens. (ii) Untreated (i.e. chilled) mince containing live larvae, mince frozen at two freezing rates, with a negative (uninfected) mince and a positive mince (infected with broken larvae) as controls, were subjected to the oral and gastric phases of a simulated digestion process. Anisakis able to survive freezing showed lower resistance to gastric fluid (i.e. faster mortality as compared to controls). Untreated larvae released significantly more antigens than freeze-surviving larvae but only after 96 h in SGF. In treatments rendering complete larvae mortality, the highest loss of larvae integrity was found upon fast freezing. There was a positive correlation between antigen release and the number of ruptures of larvae after the oral digestion phase, whereas a more complex trend was observed after oral plus gastric digestion phases.

CONCLUSION

These results suggest a new factor to consider for sensitized patients and suggest that the numbers of L3 should be reduced before industrial freezing to minimize risk. © 2020 Society of Chemical Industry.

The artificial digestion method underestimates the viability of Anisakis simplex (s.l.) L3 present in processed fish products

This work studied the performance of the artificial digestion method in terms of recovery and viability of Anisakis simplex third-stage larvae (L3) when previous treatments given to the infected fish muscle may accidentally render viable larvae. For that: a) hake mince was spiked with 10 L3/75g mince, frozen at -10, -15, -20, and -30 °C and immediately thawed, or stored for 12 or 24 h, and subjected to pepsin digestion; b) the mince was spiked under the same conditions, frozen at the above temperatures and thawed immediately. After manual recovery, L3 were assessed for viability, used to spike again the minced fish and subjected to pepsin digestion; c) the mince was spiked with 10 L3 which were: i) living (i.e. chilled), ii) freeze-surviving (live L3 had been previously recovered after freezing at -10 °C), or iii) dead (frozen at -30 °C or - 80 °C), and then subjected to pepsin digestion. Results showed that the artificial digestion method kills a significant number of larvae that may have survived freezing and thus may underestimate the number of viable larvae in a given batch. The method may also underestimate the infection level of fish batches containing dead larvae. It is suggested to take these limitations into account when designing digestion protocols for specific applications, especially when there is a risk of insufficiently treated or cooked fish batches or ready-to-eat foods.

Effectiveness of Gutting Blue Whiting (Micromesistius poutassou, Risso, 1827), in Spanish Supermarkets as an Anisakidosis Safety Measure

Anisakidosis is a parasitic zoonotic disease which can cause gastroallergic reactions in humans. In 2010, the European Food Safety Agency estimated that approximately 20,000 cases of anisakiasis had been reported across the world, with Spain having the highest number of infections in Europe. The blue whiting (Micromesistius poutassou, Risso, 1827) is one of the most widely fished species worldwide and represents around 25% of the white fish eaten in Spain. The Spanish Food Safety Authority requires obligatory evisceration of certain fish species before commercialization, but not for blue whiting. Nevertheless, some supermarkets carry this out themselves to prevent human infections and negative customer reactions deriving from the presence of ascaridoid larvae. To assess the effectiveness of eviscerations at supermarkets, a total of 320 blue whiting specimens were examined. The risk of larval migration from the visceral cavity to the musculature in gutted and ungutted fish was also assessed. Our results showed a total prevalence (25%) of ascaridoids in fish gutted at the supermarket, and a direct relationship was found between the presence of larvae in the muscle and time until evisceration. In ungutted fish, the standard length and weight were higher for infected than for non-infected fish. Also, massive infections had a higher prevalence in these larger specimens, in which the viability of larvae was also high. Larval viability was not found to be affected by a 24-h refrigeration period. Anisakis was the most prevalent genus identified in the fish examined. The results indicate that gutting at the supermarket is not an effective method for the total removal of ascaridoid larvae and that additional safety measures are advisable.

Genera and Species of the Anisakidae Family and Their Geographical Distribution

Simple Summary

The parasites of the Anisakidae family infest mainly marine mammals; however, they have the ability to infest paratenic hosts such as mollusks, small crustaceans and fish. The consumption of meat from animals of aquatic origin favors the acquisition of the disease known as Anisakiasis or Anisakidosis, depending on the species of the infecting parasite. Currently, the identification of the members of this family is carried out through the use of molecular tests, which brings about the generation of new information. The purpose of this review was to identify the genus and species of the Anisakidae family by reviewing scientific papers that used molecular tests to confirm the genus and species. The adaptability of the Anisakidae family to multiple hosts and environmental conditions allows it to have a worldwide distribution. As it is a zoonotic agent and causes non-specific clinical symptoms, it is important to know about the different members of the Anisakidae family, as well as the hosts where they have been collected.

Abstract

Nematodes of the Anisakidae family have the ability to infest a wide variety of aquatic hosts during the development of their larval stages, mainly marine mammals, aquatic birds, such as pelicans, and freshwater fish, such crucian carp, these being the hosts where the life cycle is completed. The participation of intermediate hosts such as cephalopods, shrimp, crustaceans and marine fish, is an important part of this cycle. Due to morphological changes and updates to the genetic information of the different members of the family, the purpose of this review was to carry out a bibliographic search of the genus and species of the Anisakidae family identified by molecular tests, as well as the geographical area in which they were collected. The Anisakidae family is made up of eight different parasitic genera and 46 different species. Those of clinical importance to human health are highlighted: Anisakis pegreffi, A. simplexsensu stricto, Contracaecumosculatum, Pseudoterranova azarazi, P. cattani, P. decipiens and P. krabbei. The geographical distribution of these genera and species is located mainly in the European continent, Asia and South America, as well as in North and Central America and Australia. Based on the information collected from the Anisakidae family, it was determined that the geographical distribution is affected by different environmental factors, the host and the ability of the parasite itself to adapt. Its ability to adapt to the human organism has led to it being considered as a zoonotic agent. The disease in humans manifests nonspecifically, however the consumption of raw or semi-raw seafood is crucial information to link the presentation of the parasite with the disease. The use of morphological and molecular tests is of utmost importance for the correct diagnosis of the genus and species of the Anisakidae family.

Sushi processing: microbiological hazards and the use of emerging technologies

Sushi meal has been adapting to different countries and traditions ever since it was invented. Recently there is a growing popularity of ready-to-eat sushi meals, with new sushi production plants emerging in many countries. This relatively new sushi industry is facing many challenges, one of which is the microbiological hazard related to sushi consumption. The aim of this review was to summarize the most significant aspects with regard to microbiological quality of sushi, reported cases of sushi-related poisoning, as well as the potential of modern innovative and emerging technologies to inhibit microbiological growth. Although there is a limited amount of studies in relation to sushi shelf-life extension, the existing data shows potential of using novel minimal processing technologies to improve the shelf-life and quality of sushi meals. Those technologies include the use of cold plasma, plasma activated water and electrolyzed water, as well as the use of innovative packaging and edible coatings. Based on the collected data, the possible microbiological hazards in the production process of sushi, with possible use of emerging technologies to reduce or eliminate those risks, are also emphasized.

Development and Application of Novel Chemiluminescence Immunoassays for Highly Sensitive Detection of Anisakis simplex Proteins in Thermally Processed Seafood

The third-stage larvae (L3) of Anisakis simplex are the most important source of hidden allergens in seafood products. However, there exist no commercial methods for detecting Anisakis proteins in food. Furthermore, only a few methods have been validated for the detection of A. simplex in thermally processed food. The aims of our study are (i) the development and validation of high-sensitivity chemiluminescent (CL) immunoassays for the detection of A. simplex proteins in processed seafood, (ii) and A. simplex antigen detection in common seafood products from Polish markets. We developed and validated CL sandwich ELISA (S-ELISA) and CL competitive ELISA (C-ELISA) methods for A. simplex proteins detection in food, with respective detection limits of 0.5 and 5 ng/mL. The usefulness of the assays for detecting A. simplex proteins in highly processed food was evaluated by examination of autoclaved canned fish spiked with A. simplex larvae (1–8 larvae/200 g). Commercial real-time PCR was unable to detect A. simplex in autoclaved samples at all levels of enrichment with Anisakis larvae. CL-S-ELISA was used to test various types of seafood products from Polish markets. Among all tested products (n = 259), 28% were positive. A. simplex antigens were found mostly (n = 39) in smoked fish products: mackerel, herring, cod, and hake. Other positive samples were found in marinated herrings, canned cod livers, canned mackerels, and surimi sticks. In tuna, Atlantic argentine, anchovy, sardine, sprat, and squid products, A. simplex antigens were not detected. This study provides novel effective tools for the detection of A. simplex proteins in processed food and highlights the potential allergic hazards for Anisakis-sensitized Polish consumers of seafood.

Advances in Omic Studies Drive Discoveries in the Biology of Anisakid Nematodes

Advancements in technologies employed in high-throughput next-generation sequencing (NGS) methods are supporting the spread of studies that, combined with advances in computational biology and bioinformatics, have greatly accelerated discoveries within basic and biomedical research for many parasitic diseases. Here, we review the most updated "omic" studies performed on anisakid nematodes, a family of marine parasites that are causative agents of the fish-borne zoonosis known as anisakiasis or anisakidosis. Few deposited data on Anisakis genomes are so far available, and this still hinders the deep and highly accurate characterization of biological aspects of interest, even as several transcriptomic and proteomic studies are becoming available. These have been aimed at discovering and characterizing molecules specific to peculiar developmental parasitic stages or tissues, as well as transcripts with pathogenic potential as toxins and allergens, with a broad relevance for a better understanding of host-pathogen relationships and for the development of reliable diagnostic tools.

Effect of freezing on the metabolic status of L3 larvae of Anisakis simplex s. s

The fish-borne parasite, Anisakis simplex s. s., triggers a disease called anisakiasis, that is associated with a gastrointestinal infection. The Anisakis is also associated with allergic response which may lead to anaphylactic shock. The A. simplex s. s. L3 larvae may be freeze tolerant despite when the nematodes will be cooled rapidly to -20 °C according to the sanitary authorities of the USA and the EU. The aim of this work was to study the metabolic status of A. simplex s. s. L3 larvae when frozen in terms of viability, expression of genes involved in the nematodes' survival of freezing, as well content of carbohydrates which play a cryoprotective role in thermal stress and are the main source of energy. The levels of trehalose were significantly higher after slow freezing treatment (p < .0001), than the fast freezing (p < .002). The lower temperatures induce changes, especially in trehalose synthesis gene expression, genes responsible for oxidative metabolism, and chaperone proteins, but we cannot state clearly whether these changes occur during freezing, or because they are already prevalent during cold acclimation. The induction of mentioned genes seems to be a common trait of both cold- and dehydration tolerance.

First case of human anisakiasis in Poland

Consumption of raw or inadequately processed marine fish may result in anisakidosis - a zoonotic disease caused by larvae of the parasitic nematodes of the family Anisakidae (anisakiasis when caused by members of the genus Anisakis (Nematoda: Anisakidae)), commonly found in a variety of marine fish species all over the world. Most cases of anisakidosis have been detected in the residents of Japan and South Korea, which results from the tradition of eating raw and semi-raw fish dishes. However, the disease is now increasingly often diagnosed in other parts of the world, including Europe (mainly in Spain and Italy). In Poland, no cases of human infection with anisakid nematodes have been detected so far. In this study, we report the first case of gastric anisakiasis in Poland, in a 59-year-old female patient, after eating raw Atlantic salmon (Salmo salar). The parasite was identified as the third-stage larva of Anisakis simplex sensu stricto on the basis of morphology and molecular analysis. The larva was still alive and causing pain until it was removed, which occurred more than 5 weeks after infection. The described case prove that anisakiasis should be considered as a potential cause of gastrointestinal tract ailments following the consumption of seafood in countries where no cases of this zoonosis have been reported to date.

First evidence of the presence of Anisakis simplex in Crangon crangon and Contracaecum osculatum in Gammarus sp. by in situ examination of the stomach contents of cod (Gadus morhua) from the southern Baltic Sea

Cod (Gadus morhua), an important fish species in the Baltic Sea, is the paratenic host for many parasite species, including the zoonotic nematodes, Anisakis sp. and Contracaecum osculatum. We aimed to identify which invertebrate species (found in situ in the fish stomach) are responsible for infection of cod with zoonotic nematodes. We found that Crangon crangon and Gammarus sp., both invertebrate prey species of cod, were infected with Anisakis simplex and C. osculatum, respectively. These host–parasite systems are reported here for the first time, implicating C. crangon and Gammarus sp. as sources of infection of Baltic cod with zoonotic nematodes.