Qualitative risk assessment of introduction of anisakid larvae in Atlantic salmon ( Salmo salar ) farms and commercialization of products infected with viable nematodes

Pairwise summation as a method for the additive combination of probabilities in qualitative risk assessments

Qualitative frameworks are widely employed to tackle urgent animal or public health issues when data are scarce and/or urgent decisions need to be made. In qualitative models, the degree of belief regarding the probabilities of the events occurring along the risk pathway(s) and the outcomes is described in nonnumerical terms, typically using words such as Low, Medium, or High. The main methodological challenge, intrinsic in qualitative models, relates to performing mathematical operations and adherence to the rule of probabilities when probabilities are nonnumerical. Although methods to obtain the qualitative probability from the conditional realization of n events are well-established and consistent with the multiplication rule of probabilities, there is a lack of accepted methods for addressing situations where the probability of an event occurring can increase, and the rule of probability P(AUB) = P(A) + P(B) - P(A∩B) should apply. In this work, we propose a method based on the pairwise summation to fill this methodological gap. Our method was tested on two qualitative models and compared by means of scenario analysis to other approaches found in literature. The qualitative nature of the models prevented formal validation; however, when using the pairwise summation, results consistently appeared more coherent with probability rules. Even if the final qualitative estimate can only represent an approximation of the actual probability of the event occurring, qualitative models have proven to be effective in providing scientific-based evidence to support decision-making. The method proposed in this study contributes to reducing the subjectivity that characterizes qualitative models, improving transparency and reproducibility.

Mapping the occurrence of Eustrongylides spp. in fish species caught from six lakes in Central Italy (Tuscany and Latium regions): Implications for local fishery supply chains

In the present study, in order to expand the knowledge on the distribution of parasites of the genus Eustrongylides in never investigated Italian lacustrine areas of Tuscany and Latium, fish specimens from four Tuscan lakes (Bilancino, Chiusi, Montedoglio and San Cipriano) and two Latium lakes (Bolsena and Bracciano) were collected and analyzed. The parasitological analysis, consisting of a visual inspection followed by a chloro-peptic digestion, was performed on 1650 specimens belonging to 17 species: European perch (Perca fluviatilis), Pumpkinseed (Lepomis gibbosus), Pike-perch (Sander lucioperca), Largemouth black bass (Micropterus salmoides), Pike (Esox lucius), Big-scale sand smelt (Atherina boyeri), Tench (Tinca), European Whitefish (Coregonus lavaretus), Channel catfish (Ictalurus punctatus), Chub (Squalius cephalus), Rudd (Scardinius erythrophthalmus), Common bleak (Alburnus alborella), South European roach (Sarmarutilus rubilio), South European nase (Protochondrostoma genei), Italian riffle dace (Telestes muticellus), Goldfish (Carassius auratus), and Freshwater bream (Abramis brama). Eustrongylides spp. larvae were only found in one specimen of European perch caught in Bracciano Lake and purchased from a local fishmonger (P = 3.3%; MI = 1; MA = 0.03). The only isolated Eustrongylides spp. larva was submitted to molecular analysis of the ITS gene region and identified as E. excisus. This finding adds Bracciano Lake to the list of the several Italian lakes in which nematodes belonging to this genus have been reported. Even if the observed prevalence is currently low, the presence of the parasite in this local freshwater fish supply chain requires FBOs to adopt risk management measures to prevent contaminated products from reaching final consumer. Moreover, future investigations will show if the parasite expands in these areas.

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.

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.

Sample size planning and the statistical significance of official controls by sampling

Acceptance sampling is important for food safety and is a relevant tool at production and official control levels, as it helps decision-making processes and verifies quality and food safety management. Generally, sampling plans are hypothesis tests of products that have been submitted for official appraisal and subsequent acceptance or rejection. The sample size is related to the set level of risk, the acceptable precision, and the tolerable misstatement size; therefore, sample size determination has a crucial role in setting up the accepted level of non-compliance and level of error. Using a simple predictive model based on combinatorics, this study showcases how sample size management can change the probability of rejecting good lots and/or accepting bad lots when the acceptance number is 0 (c=0). We showed that when c=0, a very high level of significance of the test corresponds to the high probability of rejecting a lot with an acceptable prevalence of defective items (type II error). We produced tables about the minimum sample size at different significance levels, which can be useful in the field. A paradigmatic example of the role of sample size in the acceptance-sampling plan is represented by the visual inspection for the detection of Anisakid larvae in fishery products. This study investigated this aspect and mainly referred to studies on the prevalence of larvae in farmed fish. We showed that, for lots ≥1000 items, the sample size is not strictly related to the lot size, but to draw a consistent control plan and reduce the variability in the clinical judgment, control authorities require a standardized approach. Because of this, the results on the prevalence of Anisakid larvae in farmed fish, if only based on sampling control plans, do not support a negligible risk statement, despite the claims reported in the EFSA opinion and several other studies.

A review of qualitative risk assessment in animal health: Suggestions for best practice

Qualitative risk assessment (QRA) can provide decision support in line with the requirement for an objective, unbiased assessment of disease risk according to the Agreement on the Application of Sanitary and Phytosanitary Measures of the World Trade Organization. However, in order for a QRA to be objective and consistently applied it is necessary to standardize the approach as much as possible. This review considers how QRAs have historically been used for the benefit of animal health, what problems have been encountered during their progression, and considers best practice for their future use. Four main elements were identified as having been the subject of some proposed standard methodology: (i) the description of risk levels, (ii) combining probabilities, (iii) accounting for trade volume and time period, and (iv) uncertainty. These elements were addressed in different ways but were highlighted as being fundamental to improving the robustness in estimating the risk and conveying the results to the risk manager with minimal ambiguity. In line with this, several tools have been developed which attempt to use mathematical reasoning to incorporate uncertainty and improve the objectivity of the qualitative framework. This represents an important advance in animal health QRA. Overall, animal health QRAs have established their usefulness by providing a tool for rapid risk estimation which can be used to identify important chains of events and critical control points along risk pathways and inform risk management programmes as to whether or not the risk exceeds a decision-making threshold above which action should be taken. Ensuring a robust objective methodology is used and that the reasons for differences in results, such as assumptions and uncertainty are clearly described to the customer with minimal ambiguity is essential to maintain confidence in the QRA process. However, further work needs to be done to determine if one objective uniform methodology should be developed and considered best practice. To this end, a set of best practice guidelines presenting the optimal way to conduct a QRA and regulated by bodies such as the World Organization for Animal Health or the European Food Safety Authority would be beneficial.

Biology, Epidemiology, Clinical Features, Diagnosis, and Treatment of Selected Fish-borne Parasitic Zoonoses

Fish-borne parasites have been part of the global landscape of food-borne zoonotic diseases for many decades and are often endemic in certain regions of the world. The past 20 years or so have seen the expansion of the range of fish-borne parasitic zoonoses to new geographic regions leading to a substantial public health burden. In this article, we summarize current knowledge about the biology, epidemiology, clinical characteristics, diagnosis, treatment and control of selected fish-borne helminthic diseases caused by parasitic roundworm (Anisakis), tapeworm (Dibothriocephalus), and fluke (Metagonimus). Humans acquire infection via consumption of raw or improperly cooked fish or fish products. The burden from these diseases is caused by morbidity rather than mortality. Infected patients may present with mild to severe gastrointestinal (eg, abdominal pain, diarrhea, and indigestion) or allergic manifestations. Patients are often admitted to the hospital or clinic with acute symptoms and no prior health problems and no travel history. Diagnosis is often established based on the detection of the diagnostic parasite stages (eg, eggs or tapeworm segments) in the patient's feces. Sometimes imaging is required to exclude other causes and avoid unnecessary surgery. Dibothriocephalus and Metagonimus are mainly treated with praziquantel. Extraction of adult Dibothriocephalus or Anisakis larvae from the bowel ensures complete elimination of the parasites and prevents a relapse of infection. The development and implementation of more efficient food safety and public health strategies to reduce the burden of zoonotic diseases attributable to fish-borne parasites is highly desirable.

Absence of anisakis nematodes in smoked farmed Atlantic salmon (Salmo salar) products on sale in European countries

The increase of global demand of aquaculture products as compensation for the lowering of fishery sustainability has shown a parallel awareness by the consumers on the importance of the safety and quality of fish products. Among these, salmon industry has reached a leading position demonstrating the negligible risk of presence of zoonotic helminths such as anisakis nematodes in farmed salmon. Despite the massive production of data in literature on parasitological surveys carried out on fresh salmon, no data are published on processed farmed salmon such as smoked products. In 2016, 270 slices of smoked farmed Atlantic salmon (Salmo salar) and 13 smoked slices from wild sockeye salmon (Oncorhynchus nerka) have been analyzed by visual inspection and UV-press method searching for the presence of anisakid nematodes. No parasites were detected in samples from farmed Atlantic salmon, while 10 out of 13 from wild salmon were positive for Anisakis simplex s.s. larvae. This first survey on the possible presence of anisakid nematodes in processed smoked salmon confirms that this risk in farmed Atlantic salmon products has to be considered negligible.

Negligible risk of zoonotic anisakid nematodes in farmed fish from European mariculture, 2016 to 2018

BackgroundThe increasing demand for raw or undercooked fish products, supplied by both aquaculture and fisheries, raises concerns about the transmission risk to humans of zoonotic fish parasites. This has led to the current European Union (EU) Regulation No 1276/2011 amending Annex III of Regulation (EC) No 853/2004 and mandating a freezing treatment of such products. Zoonotic parasites, particularly anisakid larvae, have been well documented in wild fish. Data on their presence in European aquaculture products, however, are still scarce, except for Atlantic salmon (Salmo salar), where the zoonotic risk was assessed as negligible, exempting it from freezing treatment.AimTo evaluate the zoonotic Anisakidae parasite risk in European farmed marine fish other than Atlantic salmon.MethodsFrom 2016 to 2018 an observational parasitological survey was undertaken on 6,549 farmed fish including 2,753 gilthead seabream (Sparus aurata), 2,761 European seabass (Dicentrarchus labrax) and 1,035 turbot (Scophthalmus maximus) from 14 farms in Italy, Spain and Greece. Furthermore, 200 rainbow trout (Oncorhynchus mykiss) sea-caged in Denmark, as well as 352 seabream and 290 seabass imported in Italy and Spain from other countries were examined. Fish were subjected to visual inspection and candling. Fresh visceral organs/fillet samples were artificially digested or UV pressed and visually examined for zoonotic anisakid larvae.ResultsNo zoonotic parasites were found in any of the fish investigated.ConclusionsThe risk linked to zoonotic Anisakidae in the examined fish species from European mariculture appears negligible. This study laid the groundwork for considerations to amend the current EU regulation.

A Qualitative Risk Assessment of Rabies Reintroduction Into the Rabies Low-Risk Zone of Bhutan

In Bhutan, dog-mediated rabies has been successfully eliminated from most regions of the country but remains endemic in the Southern region and sporadic incursions are also reported in the East. Elimination of rabies from the southern part of Bhutan is challenged by the porous border with the neighboring states of India which facilitates free and unregulated movement of animals. Around 17 outbreaks of rabies are reported annually in dogs and other domestic animals, posing continuous public health risks and economic losses. Furthermore, due to anthropogenic factors, such as increasing human settlements along highways, increased animal transportation, and the complex and changing human-pet relationship, there is potential to reintroduce rabies from rabies high-risk zone to rabies low-risk zone. This study was undertaken to estimate the risk of rabies re-introduction to the rabies low-risk zone by performing a qualitative risk assessment. The assessment was conducted for three risk pathways (stray dog-pathway, pet dog-pathway and cattle-pathway) under two scenarios: (1) no risk mitigation measures in place and (2) current risk mitigation measures in place. The current control measures include Government led programs, such as mass dog vaccination and dog population management, regulation of the movment of animals through pre-travel check-up and health certification, regular awareness education and rabies surveillance in the rabies endemic areas. The probability of an event occurring was assigned using the data from the available literature. Where gaps in knowledge existed, expert opinion, elicited through modified Delphi method, was used. Under the scenario in which no risk mitigation measures were in place, the risk of rabies re-introduction was estimated to be medium for the stray-dog pathway with a low level of uncertainty, low for pet-dog pathway with a low level of uncertainty, and very low for the cattle-pathway with a medium level of uncertainty. When current risk-mitigation measures were included, the risk of rabies reintroduction was estimated to be very low for the stray-dog pathway with a medium level of uncertainty, low for the pet dog-pathway with a low level of uncertainty, and extremely low for the cattle-pathway with a medium level of uncertainty. The risk of rabies re-introduction through all the pathways was greater than negligible. These findings highlight the importance of maintaining and enhancing current risk mitigation measures to prevent re-introduction of rabies into rabies low-risk zone.

Presence of Anisakidae in commercial fish species imported into the Belgian food markets: A systematic review and meta-analyses

Anisakidae are marine zoonotic nematodes with most commercial fish species as intermediate hosts. Both public health risks and socio-economic problems are attributed to these larvae. Despite these concerns, the occurrence of Anisakidae in commercial fish species in Belgium remains unknown. Therefore, the main objective of this systematic review was to look into studies assessing the prevalence and intensity (level of infection) of Anisakidae in countries importing fish to the Belgian market. The databases of PubMed, Web of Science, Cordis, Google Scholar, Google, African Journals online and Asia Journals online were searched. Main eligibility criteria were: fish species consumed in Belgium; studies conducted in one of the main importing countries; and the availability of prevalence data. From the original 519 identified studies, 83 were included with data from Spain, Germany, Chile, Denmark, Turkey, France, China, England, Belgium, Norway, Iceland, Senegal and Sweden. Overall results show a widespread occurrence of Anisakidae with a high variability in prevalence between fish species and fishing sea. Cod (Gadus morhua) and Atlantic salmon (Salmo salar), the most consumed fish species in Belgium, have a mean prevalence of 33% and 5% respectively. Of all investigated fishing zones, fish caught in the Northeast Atlantic has the highest rate of infection (68%). Furthermore, higher prevalences were found when looking at the viscera (mean prevalence 59%) compared to the muscle (29%) and with superior techniques such as enzymatic digestion or UV press (46%) compared to candling, the routine method (23%). Farmed fish were found to be the least infected (2%) but were still not Anisakidae free. The widespread presence of Anisakidae and the associated food safety implications indicate the need to further investigate the presence of Anisakidae in fish in the Belgian market.

The Significance of Mesophilic Aeromonas spp. in Minimally Processed Ready-to-Eat Seafood

Minimally processed and ready-to-eat (RTE) seafood products are gaining popularity because of their availability in retail stores and the consumers' perception of convenience. Products that are subjected to mild processing and products that do not require additional heating prior to consumption are eaten by an increasing proportion of the population, including people that are more susceptible to foodborne disease. Worldwide, seafood is an important source of foodborne outbreaks, but the exact burden is not known. The increased interest in seafood products for raw consumption introduces new food safety issues that must be addressed by all actors in the food chain. Bacteria belonging to genus Aeromonas are ubiquitous in marine environments, and Aeromonas spp. has held the title "emerging foodborne pathogen" for more than a decade. Given its high prevalence in seafood and in vegetables included in many RTE seafood meals, the significance of Aeromonas as a potential foodborne pathogen and a food spoilage organism increases. Some Aeromonas spp. can grow relatively uninhibited in food during refrigeration under a broad range of pH and NaCl concentrations, and in various packaging atmospheres. Strains of several Aeromonas species have shown spoilage potential by the production of spoilage associated metabolites in various seafood products, but the knowledge on spoilage in cold water fish species is scarce. The question about the significance of Aeromonas spp. in RTE seafood products is challenged by the limited knowledge on how to identify the truly virulent strains. The limited information on clinically relevant strains is partly due to few registered outbreaks, and to the disputed role as a true foodborne pathogen. However, it is likely that illness caused by Aeromonas might go on undetected due to unreported cases and a lack of adequate identification schemes. A rather confusing taxonomy and inadequate biochemical tests for species identification has led to a biased focus towards some Aeromonas species. Over the last ten years, several housekeeping genes has replaced the 16S rRNA gene as suitable genetic markers for phylogenetic analysis. The result is a more clear and robust taxonomy and updated knowledge on the currently circulating environmental strains. Nevertheless, more knowledge on which factors that contribute to virulence and how to control the potential pathogenic strains of Aeromonas in perishable RTE seafood products are needed.

Prevalence of anisakid parasites in fish collected from Apulia region (Italy) and quantification of nematode larvae in flesh

Anisakis spp. and Hysterothylacium spp. are nematodes that commonly parasitize several fish species. Nematode larvae can be recovered in coelomic cavity and viscera, but also in flesh and have an important economic and public health impact. A total of 1144 subjects of wild teleosts, 340 samples of cephalopods and 128 specimens of farmed fish collected from Apulia region were analysed for anisakid larvae detection by visual inspection of coelomic cavity and viscera and by digestion of the flesh. No nematode larvae were found in farmed fish and cephalopod molluscs. All examined wild-caught fish species were parasitized, except for 5 species for each of which only a few subjects belonging to the same batch were sampled, therefore the results are just indicative. A total of 6153 larvae were isolated; among these, 271 larvae were found in the muscular portion. Larvae were identified by morphological method as belonging to the genera Anisakis (97.2%) (type I and type II) and Hysterothylacium (2.8%). Both nematodes could be found in all fish species, except for round sardinella (Sardinella aurita), infected only by Hysterothylacium spp. and for Mediterranean scaldfish (Arnoglossus laterna), little tunny (Euthynnus alleteratus) and chub mackerel (Scomber japonicus) infected only with Anisakis spp.. A sample of 185 larvae was sent to the National Reference Centre for Anisakiasis (C.Re.N.A.) of Sicily for identification at the species level: 180 larvae belonged to the species A. pegreffii and 2 larvae to A. physeteris. The remaining 3 larvae were identified at genus level as Hysterothylacium. Statistical indices such as prevalence, mean intensity and mean abundance were calculated. Chub mackerel (S. japonicus) was the species with the highest prevalence and mean intensity. Moreover, the average and the median values of larvae per 100 g of edible part for each fish species were determined to estimate the consumer exposure to Anisakis spp.. The obtained values were then recalculated by referring to the edible part of all specimens (infected and non-infected) forming a single parasitized batch, getting more realistic and objective data useful for risk assessment. Our results indicate that the consumption of raw or undercooked wild fish caught off Apulian coasts could result in the acquisition of anisakiasis; on the contrary, farmed fish and cephalopods appear to be safer for the consumer.

Parasites in Food: From a Neglected Position to an Emerging Issue

Foodborne parasites have long been a neglected group of pathogens, as they often have insidious, chronic effects, rather than being acute diseases, and they are often associated with impoverished or marginalized populations. In addition, due to the long incubation period for most foodborne parasites, source attribution is often difficult, if not impossible. However, global trends have enabled foodborne parasites to emerge in different populations in new locations, transmitted through different food types, and sometimes with unexpected symptoms. This emergence of foodborne parasites has brought them into focus. In this chapter, six foodborne parasites are used as examples on emergence: Echinococcus multilocularis is spreading to new locations; Cryptosporidium spp. are beginning to be associated not only with water, but also with salads; Trypanosoma cruzi is being manifest with acute disease due to foodborne transmission, particularly transmitted with juices; Trichinella spp. have become less of a burden regarding transmission via pork in many countries, but now game animals are becoming a concern; anisakiasis is becoming a global problem as the world develops a taste for sushi, and similarly for opisthorchiasis, which is increasingly being associated with cholangiocarcinoma. However, the emergence of these foodborne parasites provides an incentive for increased efforts being made toward control. In this chapter, having described how the parasites are emerging from their neglected position, the focus turns toward control. In addition to considering control measures that may be applied to the specific parasites, an overview is provided of some of the organized collaborations, projects, and consortia, as well as some of their outputs, that have in focus the control of these emerging and important pathogens.