Prioritisation of food-borne parasites in Europe, 2016

Effectiveness and costs of interventions to reduce the within-farm Toxoplasma gondii seroprevalence on pig farms in the Netherlands

BACKGROUND

The parasite Toxoplasma gondii (T. gondii) is recognized as one of the major foodborne pathogens with a high human disease burden. To control T. gondii infections in pigs, European Food Safety Agency (EFSA) advises serological testing of pigs and audits of pig farms to identify risk factors for T. gondii infection. In line with this approach, the aim of the current study was to assess the effectiveness and costs of intervention measures implemented to reduce the T. gondii seroprevalence on finishing pig farms in the Netherlands. A crossover clinical trial was conducted at five case farms were their own control and the cross-over moment was the implementation of interventions to reduce risk factors. Each of the case farms had a farm-specific intervention strategy with one principal intervention measure (neutering of cats, professional rodent control or covering food storage).

RESULTS

All finishing pig farms (n = 5) showed a reduction in T. gondii seroprevalence within one year of implementing the intervention strategy. Cat neutering (n = 3) and feed coverage (n = 1) showed statistically significant reductions in seroprevalence. Rodent control (n = 1) did not show a statistically significant reduction. The estimated reduction in seroprevalence in response to the neutering of cats and feed coverage were 67 and 96 %, respectively.

CONCLUSIONS

Our work demonstrates that it is possible to reduce the within-farm T. gondii seroprevalence within one year after interventions were implemented to reduce T. gondii risk factors. This information is essential and encouraging for policy makers, food business operators, and farmers to implement in their risk assessment and to apply to food safety control systems.

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.

Molecular and evolutionary basis for survival, its failure, and virulence factors of the zoonotic nematode Anisakis pegreffii

Parasitism is a highly successful life strategy and a driving force in genetic diversity that has evolved many times over. Accidental infections of non-targeted hosts represent an opportunity for lateral host switches and parasite niche expansion. However, if directed toward organisms that are phylogenetically distant from parasite's natural host, such as humans, it may present a dead-end environment where the parasite fails to mature or is even killed by host immunity. One example are nematodes of Anisakidae family, genus Anisakis, that through evolution have lost the ability to propagate in terrestrial hosts, but can survive for a limited time in humans causing anisakiasis. To scrutinize versatility of Anisakis to infect an evolutionary-distant host, we performed transcriptomic profiling of larvae successfully migrating through the rat, a representative model of accidental human infection and compared it to that of larvae infecting an evolutionary-familiar, paratenic host (fish). In a homeothermic accidental host Anisakis upregulated ribosome-related genes, cell division, cuticle constituents, oxidative phosphorylation, in an unsuccessful attempt to molt to the next stage. In contrast, in the paratenic poikilothermic host where metabolic pathways were moderately upregulated or silenced, larvae prepared for dormancy by triggering autophagy and longevity pathways. Identified differences and the modelling of handful of shared transcripts, provide the first insights into evolution of larval nematode virulence, warranting their further investigation as potential drug therapy targets.

HERBIVORES AS ACCIDENTAL HOSTS FOR TRICHINELLA: SEARCH FOR EVIDENCE OF TRICHINELLA INFECTION AND EXPOSURE IN FREE-RANGING MOOSE (ALCES ALCES) IN A HIGHLY ENDEMIC SETTING

Herbivores can be accidental hosts for the zoonotic nematode parasites Trichinella spp., which are endemic at high prevalence in wildlife in northeastern Europe. Using direct and indirect detection methods for Trichinella spp., we investigated samples from 463 wild moose (Alces alces) harvested by hunters in Estonia in 2015. A total of 460 moose were tested directly by artificial digestion of diaphragm muscle, 463 moose were tested indirectly by enzyme-linked immunosorbent assay (ELISA), and 34 moose also by western blot. Positive-control reference sera were from other host species. Nematode larvae were found in six muscle samples; five of which were pooled samples. None of the larvae were identified as Trichinella spp., based on their morphology and molecular analyses. Twelve moose (2.6%) were positive by ELISA, but none were positive by the western blot test. Trichinella spp. infection was not detected, but ELISA results may suggest Trichinella spp. exposure in a small proportion of moose in Estonia.

Blue mussel (Mytilus edulis)-A bioindicator of marine water contamination by protozoa: Laboratory and in situ approaches

AIMS

The protozoan parasites Cryptosporidium spp., Giardia duodenalis and Toxoplasma gondii are identified as public health priorities and are present in a wide variety of environments including the marine ecosystem. The objective of this study was to demonstrate that the marine bivalve blue mussel (Mytilus edulis) can be used as a tool to monitor the contamination of marine waters by the three protozoa over time.

METHODS AND RESULTS

In order to achieve a proof of concept, mussels were exposed to three concentrations of G. duodenalis cysts and Cryptosporidium parvum/T. gondii oocysts for 21 days, followed by 21 days of depuration in clear water. Then, natural contamination by these protozoa was sought for in wild marine blue mussels along the northwest coast of France to validate their relevance as bioindicators in the field. Our results highlighted that: (a) blue mussels bioaccumulated the parasites for 21 days, according to the conditions of exposure, and parasites could still be detected during the depuration period (until 21 days); (b) the percentage of protozoa-positive M. edulis varied under the degree of protozoan contamination in water; (c) mussel samples from eight out of nine in situ sites were positive for at least one of the protozoa.

CONCLUSIONS

The blue mussel M. edulis can bioaccumulate protozoan parasites over long time periods, according to the degree of contamination of waters they are inhabiting, and can highlight recent but also past contaminations (at least 21 days).

SIGNIFICANCE AND IMPACT OF THE STUDY

Mytilus edulis is a relevant bioaccumulators of protozoan (oo)cysts in laboratory and field conditions, hence its potential use for monitoring parasite contamination in marine waters.

First Report of Echinococcus ortleppi in Free-Living Wild Boar (Sus scrofa) from Portugal

Cystic echinococcosis (CE) is a zoonosis that is prevalent worldwide. It is considered endemic in Portugal but few studies have been performed on Echinococcus granulosus sensu lato and their hosts. In this study, CE cysts are reported for the first time in a free-living wild boar (Sus scrofa) in Portugal. The presence of the metacestodes in the liver of the wild boar was identified by morphological features, microscopic examination and molecular analysis. The sequencing of part of the DNA nuclear ribosomal internal transcribed spacer-1 (ITS-1) region revealed a G5 genotype that presently corresponds to Echinococcus ortleppi. This is the first report of E. ortleppi in Portugal and to the best of the authors’ knowledge, in Europe. These results suggest that wild boar may be a host of CE, namely, crossing the livestock–wildlife interface, which has important public health implications. Wildlife reservoirs must be taken into account as CE hosts and surveillance of game as well as health education for hunters should be implemented using a One Health approach, with implementation of feasible and tailor-made control strategies, namely, proper elimination of byproducts in the field.

Detection of Cyclospora cayetanensis, Echinococcus multilocularis, Toxocara spp. and microsporidia in fresh produce using molecular methods: - A review

The current trend for a healthy lifestyle corresponds with a healthy diet, which is associated with regular and frequent consumption of raw fruit and vegetables. However, consumption of ready-to-eat (RTE) food without heat treatment or sufficient washing may pose a risk to consumers. Among the well-known protozoan parasites associated with RTE food and water are Cryptosporidium spp., Giardia duodenalis and Toxoplasma gondii. These belong among prioritized parasitic pathogens, as they are associated with numerous disease outbreaks in humans all around the world. Nevertheless, other parasitic agents such as Cyclospora cayetanensis, Toxocara cati, Toxocara canis, Echinococcus multilocularis and zoonotic microsporidia should not be neglected. Although these selected parasites belong to phylogenetically diverse groups, they have common characteristics associated with fresh produce and each of them poses a health risk to humans. Ensuring healthy food is produced requires the standartization of laboratory methods for the detection of parasitic agents. This article reviews the molecular methods currently used in laboratories for detection of Cyclospora cayetanensis, Toxocara cati, Toxocara canis, Echinococcus multilocularis and zoonotic microsporidia in fresh produce.

Collaborative Studies for the Detection of Taenia spp. Infections in Humans within CYSTINET, the European Network on Taeniosis/Cysticercosis

Laboratory tools for diagnosing taeniosis/cysticercosis in non-endemic countries are available; however, there is little data on their performance. To provide information on the sensitivity, specificity, and reproducibility of these tools, inter-laboratory studies were organized within the EU COST-Action CYSTINET (TD1302). Two serological and one coprological Ring Trials (RTs) were organized to test a panel of human-derived sera and stool samples using assays routinely conducted by the participating laboratories to detect Taenia spp. infections. Four Western blots (WBs) and five ELISAs were used by nine laboratories for cysticercosis diagnosis. In the first serological RT, the overall sensitivity was 67.6% (95% CI, 59.1–75.4), whereas specificity was 97% (95% CI, 89.8–99.6). WBs recorded the best accuracy. A second serological RT was organized, to assess the three tests most frequently used during the first RT. Two out of six laboratories performed all the three tests. The overall sensitivity and specificity were 52.8% (95% CI, 42.8–62.7) and 98.1% (95% CI, 93.2–99.7), respectively. Laboratory performance strongly affected test results. Twelve laboratories participated in the coprological RT using conventional microscopy and six laboratories used molecular assays. Traditional diagnosis by microscopy yielded better results than molecular diagnosis. This may have been influenced by the lack of standardization of molecular tests across participating laboratories.

Contamination of fresh produce sold on the Italian market with Cyclospora cayetanensis and Echinococcus multilocularis

To investigate the presence of Cyclospora cayetanensis, Toxoplasma gondii and Echinococcus spp. in fresh produce sold in Italy, 324 locally produced 'ready-to-eat' (RTE) mixed-salad packages belonging to three brands and 324 berries packages (blueberries and blackberries imported from Peru and Mexico, respectively, and raspberries grown in Italy) were purchased at retail. Nine individual packages from each of the six types of fresh produce were collected monthly for one year, and with the same produce pooled, this resulted in a total of 72 pools for the whole year. Using microscopy (FLOTAC), a Cyclospora-like oocyst was detected in a blueberry sample and a taeniid egg was detected in a RTE-salad sample. Molecular tools confirmed these to be C. cayetanensis and Echinococcus multilocularis, respectively. Toxoplasma gondii was not detected in any of the samples. This study shows for the first time in Europe that imported berries on the Italian market may be contaminated with C. cayetanensis and RTE salads grown in Italy with E. multilocularis. The results indicate a new epidemiological scenario and highlight that current management of fresh produce, locally produced or imported, does not ensure products are free from parasite contamination.

Mathematical modelling of Toxoplasma gondii transmission: A systematic review

BACKGROUND

Toxoplasma gondii is a ubiquitous protozoan parasite that can infect virtually all warm-blooded animals. It is the causative agent of toxoplasmosis, a significant public health issue worldwide. Mathematical models are useful to study the transmission dynamics of T. gondii infection in different settings, and may be used to compare the effectiveness of prevention measures.

METHODS

To obtain an overview of existing mathematical models for transmission of T. gondii, a systematic review was undertaken. The review was conducted according to an a priori protocol and the results were reported according to the PRISMA guidelines. Specific search terms were developed and used in the search of three databases (Scopus, PubMed, and Embase).

RESULTS

In total, 484 unique records were retrieved from the systematic search. Among them, 15 studies that used mathematical models to study the transmission of T. gondii. These studies were categorized into four groups based on the primary aims: dynamics of transmission (n = 8), intervention (n = 5), spatial distribution (n = 1), and outbreak investigation (n = 1).

CONCLUSIONS

Considering the high disease burden caused by T. gondii, the number of studies using mathematical models to understand the transmission dynamics of this parasite and to evaluate the effectiveness of intervention measures was only 15. This systematic review provides an overview of existing mathematical models and identifies the data gaps for model building. The results from this study can be helpful for further development of mathematical models and improved understanding of the transmission dynamics of T. gondii infection.

Intrinsic properties of anisakid nematode larvae as a potential tool for the detection in fish products

Anisakid nematode larvae (NL) in fish products comprise a risk to human health and, if visible, lead to the rejection of these products by consumers. Therefore, great efforts are being made for the identification of these anisakid larvae to estimate the potential consumer health risk as well as to develop effective detection methods in order to prevent the introduction of heavily infected fish products into the market. The tasks of national reference laboratories include the improvement of detection methods and to promote their further development. As a prerequisite for improved detection, it is important to understand the structural properties of anisakid NL and compounds produced during host-parasite interactions. This review provides an overview of the intrinsic properties of anisakid NL and reports the latest detection methods in published literature. First, in order to define the potentially interesting intrinsic properties of anisakid nematodes for their detection, anatomy and compounds involved in host-parasite interactions are summarised. These can be used for various detection approaches, such as in the medical field or for allergen detection in fish products. In addition, fluorescence characteristics and their use as both established and promising candidates for detection methods, especially in the field of optical sensing technologies, are presented. Finally, different detection and identification methods applied by the fish processing industries and by control laboratories are listed. The review intends to highlight trends and provide suggestions for the development of improved detection and identification methods of anisakid NL in fish products.

Surveillance of foodborne parasitic diseases in Europe in a One Health approach

In 2012, WHO/FAO ranked 24 foodborne parasites (FBP) using multicriteria decision analysis (MCDA) to provide risk assessors with a basis for prioritising control of highly ranked FBP on the global level. One conclusion was that ranking may differ substantially per region. In Europe, the same methodology was used to rank FBP of relevance for Europe. Of the 24 FBP, the top-five prioritised FBP were identified for Europe as Echinococcus multilocularis, Toxoplasma gondii, Trichinella spiralis, E. granulosus, and Cryptosporidium spp., all of which are zoonotic. The objective of the present study was to provide an overview of surveillance and reporting systems in Europe for these top five prioritised FBP in the human and animal populations, to identify gaps, and give recommendations for improvement. Information on the surveillance systems was collected from 35 European countries and analysed according to the five different regions. For most FBP, human surveillance is passive in most countries and regions in Europe and notification differs between countries and regions. Adequate surveillance programmes for these FBP are lacking, except for T. spiralis, which is notifiable in 34 countries with active surveillance in susceptible animals under EU directive. Although human and animal surveillance data are available for the five prioritised FBP, we identified a lack of consistency in surveillance and reporting requirements between national experts and European bodies. Recommendations for improved surveillance systems are discussed.

Trichinella spp. in Wild Boars (Sus scrofa), Brown Bears (Ursus arctos), Eurasian Lynxes (Lynx lynx) and Badgers (Meles meles) in Estonia, 2007-2014

Simple Summary

Trichinellosis is an important foodborne zoonosis. In Estonia, Trichinella infections are endemic in wild animals. This paper summarizes findings of Trichinella-parasites during an 8-year period in Estonia in selected host species: wild boars, brown bears, Eurasian lynxes, and badgers. The results highlight that testing wildlife hunted for human consumption for Trichinella is important, and that there is room for improvement in the proportion of hunted animals tested.

Abstract

In this study, we summarize Trichinella findings from four wild, free-ranging host species from Estonia during 2007–2014. Trichinella spp. larvae were detected in 281 (0.9%, 95% confidence interval (CI) 0.8–1.0) of 30,566 wild boars (Sus scrofa), 63 (14.7%, 95% CI 11.6–18.3) of 429 brown bears (Ursus arctos), 59 (65.56%, 95% CI 55.3–74.8) of 90 Eurasian lynxes (Lynx lynx), and three (60.0%, 95% CI 18.2–92.7) of five badgers (Meles meles). All four European Trichinella species were detected: T. britovi in 0.7% of the wild boars, 7.2% of the brown bears, 45.6% of the lynxes, and 40.0% of the badgers; T. nativa in 0.1% of the wild boars, 5.8% of the brown bears, and 20.0% of the lynxes; T. pseudospiralis in 0.02% the wild boars; and T. spiralis in 0.03% of the wild boars and 4.4% of the lynxes. The results include the first description from Estonia of T. britovi in brown bear and badgers, T. pseudospiralis in wild boars, and T. spiralis in wild boars and lynxes. The results indicate high infection pressure in the sylvatic cycles across the years—illustrating continuous risk of spillover to domestic cycles and of transmission to humans.

Molecular Methods for the Detection of Toxoplasma gondii Oocysts in Fresh Produce: An Extensive Review

Human infection with the important zoonotic foodborne pathogen Toxoplasma gondii has been associated with unwashed raw fresh produce consumption. The lack of a standardised detection method limits the estimation of fresh produce as an infection source. To support method development and standardisation, an extensive literature review and a multi-attribute assessment were performed to analyse the key aspects of published methods for the detection of T. gondii oocyst contamination in fresh produce. Seventy-seven published studies were included, with 14 focusing on fresh produce. Information gathered from expert laboratories via an online questionnaire were also included. Our findings show that procedures for oocyst recovery from fresh produce mostly involved sample washing and pelleting of the washing eluate by centrifugation, although washing procedures and buffers varied. DNA extraction procedures including mechanical or thermal shocks were identified as necessary steps to break the robust oocyst wall. The most suitable DNA detection protocols rely on qPCR, mostly targeting the B1 gene or the 529 bp repetitive element. When reported, validation data for the different detection methods were not comparable and none of the methods were supported by an interlaboratory comparative study. The results of this review will pave the way for an ongoing development of a widely applicable standard operating procedure.

Echinococcus multilocularis and other cestodes in red foxes (Vulpes vulpes) of northeast Italy, 2012-2018

Background

Echinococcus multilocularis is a small tapeworm affecting wild and domestic carnivores and voles in a typical prey-predator life cycle. In Italy, there has been a focus of E. multilocularis since 1997 in the northern Italian Alps, later confirmed in red foxes collected from 2001 to 2005. In this study, we report the results of seven years of monitoring on E. multilocularis and other cestodes in foxes and describe the changes that occurred over time and among areas (eco-regions) showing different environmental and ecological features on a large scale.

Methods

Eggs of cestodes were isolated from feces of 2872 foxes with a sedimentation/filtration technique. The cestode species was determined through multiplex PCR, targeting and sequencing ND1 and 12S genes. Analyses were aimed to highlight variations among different eco-regions and trends in prevalence across the study years.

Results

Out of 2872 foxes, 217 (7.55%) samples resulted positive for cestode eggs at coproscopy, with differences of prevalence according to year, sampling area and age class. Eight species of cestodes were identified, with Taenia crassiceps (2.65%), Taenia polyacantha (1.98%) and E. multilocularis (1.04%) as the most represented. The other species, Mesocestoides litteratus, Taenia krabbei, T. serialis, T. taeniaeformis and Dipylidium caninum, accounted for < 1% altogether. Echinococcus multilocularis was identified in foxes from two out of six eco-regions, in 30 fecal samples, accounting for 1.04% within the cestode positives at coproscopy. All E. multilocularis isolates came from Bolzano province. Prevalence of cestodes, both collectively and for each of the three most represented species (T. crassiceps, T. polyacantha and E. multilocularis), varied based on the sampling year, and for E. multilocularis an apparent increasing trend across the last few years was evidenced.

Conclusions

Our study confirms the presence of a focus of E. multilocularis in red foxes of northeast Italy. Although this focus seems still spatially limited, given its persistence and apparent increasing prevalence through the years, we recommend research to be conducted in the future on the ecological factors that, on a smaller scale, allow this zoonotic species to persist. On the same scale, we recommend a health education campaign to inform on the measures to prevent this zoonosis, targeted at people living in the area, especially hunters, dog owners, forestry workers and other potentially exposed categories.

Acute Anisakiasis: Pharmacological Evaluation of Various Drugs in an Animal Model

BACKGROUND

The accidental ingestion of the third larval stage of Anisakis can cause acute clinical symptoms, which are relieved via extraction of the larvae. Although this is a highly effective technique, it can only be practiced when the larvae are found in accessible areas of the gastrointestinal tract, and therefore instead the condition has often been treated using various different drugs.

AIMS

This study evaluates the effectiveness of gastric acid secretion inhibitors (omeprazole and ranitidine), gastric mucosal protectants (sucralfate) and anthelmintics (mebendazole and flubendazole) in treating anisakiasis in Wistar rats.

METHODS

Rats were infected with Anisakis-type I larvae and administered the drugs via a gastric probe. Data were recorded regarding the number of live and dead larvae, their location both within the animal and in its feces, and the presence of gastrointestinal lesions. Additionally, gastric pH was measured and histology performed.

RESULTS

While rats in all experimental groups exhibited lesions; those treated with ranitidine and mebendazole showed significantly fewer lesions (50% and 35% of rats exhibited lesions, respectively). Histological examination of the gastric lesions revealed infection-induced changes, but no significant differences were observed between the treated and untreated rats.

CONCLUSIONS

Mebendazole was found to be most efficacious in preventing gastrointestinal lesions, followed by ranitidine, which was the most effective antacid of those studied. Both these drugs could thus be considered as part of the conservative management of anisakiasis.

Echinococcus granulosus sensu lato and Echinococcus multilocularis: A review

Echinococcus spp. have a global distribution and are found on every continent except Antarctica. Infections with these parasites are considered extremely serious, contributing to significant morbidity and mortality in addition to substantial economic losses to the livestock industry. Echinococcus granulosus sensu lato (s.l.) and Echinococcus multilocularis, causing cystic echinococcosis (CE) and alveolar echinococcosis (AE) respectively, are the two main species of interest from a human and veterinary perspective. This review collates the current state-of-the-art understanding of these two parasites within four key areas of relevance to human and veterinary professionals: transmission and epidemiology, clinical signs and pathogenesis, diagnosis, and treatment and prevention. This review should serve as a broad introduction to the most important Echinococcus spp. The reader is advised to seek out specific literature on individual diseases and their causative parasites for a deeper understanding.

[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.

Proteomic Insights into the Biology of the Most Important Foodborne Parasites in Europe

Foodborne parasitoses compared with bacterial and viral-caused diseases seem to be neglected, and their unrecognition is a serious issue. Parasitic diseases transmitted by food are currently becoming more common. Constantly changing eating habits, new culinary trends, and easier access to food make foodborne parasites' transmission effortless, and the increase in the diagnosis of foodborne parasitic diseases in noted worldwide. This work presents the applications of numerous proteomic methods into the studies on foodborne parasites and their possible use in targeted diagnostics. Potential directions for the future are also provided.

A two-step morphology-PCR strategy for the identification of nematode larvae recovered from muscles after artificial digestion at meat inspection

To ensure that meat from livestock and game is safe for human consumption, European legislation lays down rules for mandatory testing. Helminth larvae are a category of zoonotic foodborne pathogens that can contaminate meat. Among helminths, the only zoonotic nematode regulated in Europe regarding meat inspection is Trichinella spp.. It is precisely during Trichinella testing that other potentially zoonotic larvae can be found. Due to current lack of tools, their identification is often very complicated. Nematode larvae other than Trichinella, recovered from artificial digestions of pig and wild boar muscles from France and Germany, were subjected to a newly developed two-step identification scheme, which includes both morphological examination and molecular assays. The first step is a general orientation towards a broad taxonomic group; the second step consists of targeted identification based on the results of first step. Different parasites were identified, some of which were not zoonotic such as Metastrongylus spp. and Angiostrongylus vasorum, but others are known to be zoonotic such as Toxocara cati, Ascaris suum, and Uncinaria stenocephala. The strategy is efficient for the identification of nematode larvae recovered from muscles but could also be applied for larvae from other sources.

Veterinary Students Have a Higher Risk of Contracting Cryptosporidiosis when Calves with High Fecal Cryptosporidium Loads Are Used for Fetotomy Exercises

Cryptosporidium spp. can cause severe diarrhea in infected individuals. Cryptosporidium parvum is zoonotic, and cattle are the main reservoir. In several countries, outbreaks of cryptosporidiosis have occurred in veterinary students after handling calves. We carried out a 1-year-long prospective study to investigate the occurrence of these recurrent cryptosporidiosis outbreaks in Denmark. Our investigation used a One Health approach and combined comprehensive epidemiological approaches and laboratory methods applied to both students and calves in the setting of the fetotomy exercises. Two outbreaks took place during the study period; additionally, we retrospectively identified two more suspected outbreaks prior to the study period. The results illustrated a high risk of contracting cryptosporidiosis among veterinary students in the setting of the fetotomy exercises, especially when using calves with high fecal Cryptosporidium loads. Our data can be used to inform future efforts to prevent transmission of Cryptosporidium parvum to students during fetotomy exercises.

An outbreak of cryptosporidiosis among veterinary students performing fetotomy exercises on euthanized calves took place in September 2018 in Denmark. A prospective cohort investigation was performed to identify risk factors and provide guidance for preventing outbreaks of cryptosporidiosis in this setting. Ninety-seven students attended the fetotomy exercises and completed a questionnaire about symptoms and potential risk behavior. Real-time PCR was used to detect Cryptosporidium spp. in stool samples from students and to quantify the fecal parasite load in the calves used for the exercises. gp60 subtyping was carried out for the Cryptosporidium-positive samples. Our case definition was based on participation in a fetotomy exercise, reported symptoms, and laboratory results. Eleven laboratory-confirmed or probable cases (11%) were identified in two outbreaks during the prospective study period, with attack rates of 4/10 (40%) and 7/9 (78%), respectively. The risk factors for cryptosporidiosis we identified were performing the exercise on a diarrheic calf, reporting visible fecal contamination on the personal protective equipment (PPE), and reporting problems with PPE during the exercise. Cryptosporidium parvum IIaA15G2R1 was detected in both cases and calves. A significantly higher proportion of the calves aged 7 days old and above were positive compared with younger calves. Furthermore, a high fecal Cryptosporidium load in a calf was associated with a higher probability of an outbreak among the students. Based on our results, using noninfected calves for the exercises, appropriate use of PPE, and thorough hand hygiene are recommended to reduce the risk of contracting cryptosporidiosis in connection with fetotomy exercises.

IMPORTANCECryptosporidium spp. can cause severe diarrhea in infected individuals. Cryptosporidium parvum is zoonotic, and cattle are the main reservoir. In several countries, outbreaks of cryptosporidiosis have occurred in veterinary students after handling calves. We carried out a 1-year-long prospective study to investigate the occurrence of these recurrent cryptosporidiosis outbreaks in Denmark. Our investigation used a One Health approach and combined comprehensive epidemiological approaches and laboratory methods applied to both students and calves in the setting of the fetotomy exercises. Two outbreaks took place during the study period; additionally, we retrospectively identified two more suspected outbreaks prior to the study period. The results illustrated a high risk of contracting cryptosporidiosis among veterinary students in the setting of the fetotomy exercises, especially when using calves with high fecal Cryptosporidium loads. Our data can be used to inform future efforts to prevent transmission of Cryptosporidium parvum to students during fetotomy exercises.

Prevalence of Cryptosporidium in pigs in China: A systematic review and meta-analysis

Cryptosporidium is an important zoonotic parasite that can infect a variety of hosts, including pigs and humans, through water and food. Many studies on Cryptosporidium infection in pigs have been reported worldwide. However, the meta-analysis of Cryptosporidium infection in pigs in China has not been published. This study retrieved articles related to Cryptosporidium in pigs in China by using four databases: Chinese National Knowledge Infrastructure (CNKI), PubMed, VIP Chinese journal database and Wanfang Data. We retrieved 40 studies related to Cryptosporidium infection in China, and those articles were harvested from the inception to 1 January 2020. We estimated that the overall prevalence of pigs with Cryptosporidium in the selected period was 12.2% (4,349/30,404). In the sampling year subgroup, the prevalence rate after 2010 was the lowest at 8.7% (2,087/18,100). In Northern China, the Cryptosporidium prevalence was 47.9% (34/71). By contrast, the prevalence of Cryptosporidium in Southwestern China was only 6.9% (778/6,445). The infection rate of Cryptosporidium in diarrhoea pigs of 15.6% (74/384) was higher than that in non-diarrhoea pigs at 10.8% (378/2,840). Among the four age groups, the prevalence of weaning pigs of 16.2% (530/3,243) was the highest, and the difference was significant (p < .05). The prevalence of Cryptosporidium in extensive farming was 25.7% (660/3,121), which was significantly higher than in intensive farming 8.7% (566/6,336), and the prevalence of infection was related to the farming modes (p < .05). We also analysed the impact of different geographic factor subgroups (longitude, latitude, precipitation, temperature, humidity, climate and altitude) on the prevalence of pigs. The results showed that cryptosporidiosis was widespread in pigs in China. We suggest that appropriate control schemes should be developed according to the differences in breeding patterns and geographic conditions in different regions, and effective management measures should be developed to reduce the spread between pigs.

Health sequelae of human cryptosporidiosis in industrialised countries: a systematic review

BACKGROUND

Cryptosporidium is a protozoan parasite which is a common cause of gastroenteritis worldwide. In developing countries, it is one of the most important causes of moderate to severe diarrhoea in young children; in industrialised countries it is a cause of outbreaks of gastroenteritis associated with drinking water, swimming pools and other environmental sources and a particular concern in certain immunocompromised patient groups, where it can cause severe disease. However, over recent years, longer-term sequelae of infection have been recognised and a number of studies have been published on this topic. The purpose of this systematic review was to examine the literature in order to better understand the medium- to long-term impact of cryptosporidiosis.

METHODS

This was a systematic review of studies in PubMed, ProQuest and Web of Science databases, with no limitations on publication year or language. Studies from any country were included in qualitative synthesis, but only those in industrialised countries were included in quantitative analysis.

RESULTS

Fifteen studies were identified for qualitative analysis which included 3670 Cryptosporidium cases; eight studies conducted in Europe between 2004-2019 were suitable for quantitative analysis, including five case-control studies. The most common reported long-term sequelae were diarrhoea (25%), abdominal pain (25%), nausea (24%), fatigue (24%) and headache (21%). Overall, long-term sequelae were more prevalent following infection with Cryptosporidium hominis, with only weight loss and blood in stool being more prevalent following infection with Cryptosporidium parvum. Analysis of the case-control studies found that individuals were 6 times more likely to report chronic diarrhoea and weight loss up to 28 months after a Cryptosporidium infection than were controls. Long-term abdominal pain, loss of appetite, fatigue, vomiting, joint pain, headache and eye pain were also between 2-3 times more likely following a Cryptosporidium infection.

CONCLUSIONS

This is the first systematic review of the long-term sequelae of cryptosporidiosis. A better understanding of long-term outcomes of cryptosporidiosis is valuable to inform the expectations of clinicians and their patients, and public health policy-makers regarding the control and prevention of this infection. Systematic review registration PROSPERO Registration number CRD42019141311.

Parasites in the changing world - Ten timely examples from the Nordic-Baltic region

The world is changing, and parasites adapt. The Nordic-Baltic region in northern Europe - including the Nordic countries Denmark, Finland, Iceland, Norway and Sweden, and the Baltic States Estonia, Latvia and Lithuania - is facing new parasitological challenges due to changes in populations of parasites and their hosts and the spread of new parasites to the region due to climate change. Some changes can also be ascribed to increased awareness and detection. In this paper, we review and discuss a convenience selection of ten timely examples of recent observations that exemplify trends and challenges from different fields of parasitology, with particular focus on climate change and potential changes in epidemiology of pathogens in northern Europe. The examples illustrate how addressing parasitological challenges often requires both intersectoral and international collaboration, and how using both historical baseline data and modern methodologies are needed.

Cysticercosis and taeniasis cases diagnosed at two referral medical institutions, Belgium, 1990 to 2015

Background

Few case reports on human infections with the beef tapeworm Taenia saginata and the pork tapeworm, Taenia solium, diagnosed in Belgium have been published, yet the grey literature suggests a higher number of cases.

Aim

To identify and describe cases of taeniasis and cysticercosis diagnosed at two Belgian referral medical institutions from 1990 to 2015.

Methods

In this observational study we retrospectively gathered data on taeniasis and cysticercosis cases by screening laboratory, medical record databases as well a uniform hospital discharge dataset.

Results

A total of 221 confirmed taeniasis cases were identified. All cases for whom the causative species could be determined (170/221, 76.9%) were found to be T. saginata infections. Of those with available information, 40.0% were asymptomatic (26/65), 15.4% reported diarrhoea (10/65), 9.2% reported anal discomfort (6/65) and 15.7% acquired the infection in Belgium (11/70). Five definitive and six probable cases of neurocysticercosis (NCC), and two cases of non-central nervous system cysticercosis (non-CNS CC) were identified. Common symptoms and signs in five of the definitive and probable NCC cases were epilepsy, headaches and/or other neurological disorders. Travel information was available for 10 of the 13 NCC and non-CNS CC cases; two were Belgians travelling to and eight were immigrants or visitors travelling from endemic areas.

Conclusions

The current study indicates that a non-negligible number of taeniasis cases visit Belgian medical facilities, and that cysticercosis is occasionally diagnosed in international travellers.

Molecular Characterization of Echinococcus granulosus sensu lato from Humans in Slovenia

The larval form of tapeworms of the Echinococcus granulosus sensu lato species cluster cause an important zoonotic infection, cystic echinococcosis (CE). Molecular characterization of the cluster’s isolates from different hosts greatly contributes to a better understanding of its transmission dynamics. To date, no genetic information is available on CE in Slovenia. In this work, we characterized isolates from human CE cases. Parasite samples from 18 patients were collected, together with the patients’ demographic and clinical data. Genomic DNA was analyzed by conventional PCR and sequencing at four mitochondrial loci (cytochrome c oxidase subunit 1, cox1; NADH dehydrogenase subunit 1, nad1; NADH dehydrogenase subunit 5, nad5; and small ribosomal RNA, rrnS). Thirteen isolates were successfully amplified and sequenced. Seven (58.8%) patients were infected with E. granulosus sensu stricto (s.s.) G1, five (38.5%) with E. canadensis G7 and one (7.7%) with E. granulosus s.s. G3. Echinococcus canadensis G7, the pig genotype, was identified exclusively in autochthonous Slovenes, while the patients originating from the Western Balkans were all infected with E. granulosus s.s. Our findings suggest that pigs are important intermediate hosts for human CE in Slovenia.

Drug repurposing applied: Activity of the anti-malarial mefloquine against Echinococcus multilocularis

The current chemotherapeutical treatment against alveolar echinococcosis relies exclusively on benzimidazoles, which are not parasiticidal and can induce severe toxicity. There are no alternative treatment options. To identify novel drugs with activity against Echinococcus multilocularis metacestodes, researchers have studied potentially interesting drug targets (e.g. the parasite's energy metabolism), and/or adopted drug repurposing approaches by undertaking whole organism screenings. We here focus on drug screening approaches, which utilize an in vitro screening cascade that includes assessment of the drug-induced physical damage of metacestodes, the impact on metacestode viability and the viability of isolated parasite stem cells, structure-activity relationship (SAR) analysis of compound derivatives, and the mode of action. Finally, once in vitro data are indicative for a therapeutic window, the efficacy of selected compounds is assessed in experimentally infected mice. Using this screening cascade, we found that the anti-malarial mefloquine was active against E. multilocularis metacestodes in vitro and in vivo. To shed more light into the mode of action of mefloquine, SAR analysis on mefloquine analogues was performed. E. multilocularis ferritin was identified as a mefloquine-binding protein, but its precise role as a drug target remains to be elucidated. In mice that were infected either intraperitoneally with metacestodes or orally with eggs, oral treatment with mefloquine led to a significant reduction of parasite growth compared to the standard treatment with albendazole. However, mefloquine was not acting parasiticidally. Assessment of mefloquine plasma concentrations in treated mice showed that levels were reached which are close to serum concentrations that are achieved in humans during long-term malaria prophylaxis. Mefloquine might be applied in human AE patients as a salvage treatment. Future studies should focus on other repurposed anti-infective compounds (MMV665807, niclosamide, atovaquone), which showed stronger in vitro activity against E. multilocularis than mefloquine.

Source attribution of human echinococcosis: A systematic review and meta-analysis

BACKGROUND

A substantial proportion of echinococcosis transmission to humans via contamination of food has been assumed. However, the relative importance of food as a transmission vehicle has previously been estimated through expert opinion rather than empirical data.

OBJECTIVE

To find and evaluate empirical data that could be used to estimate the source attribution of echinococcosis, in particular the proportion that is transmitted through contaminated food.

METHODS

A systematic review was undertaken to identify reports on the risk factors for human cystic (CE) and alveolar (AE) echinococcosis. Data bases searched included PubMed, Scopus, Web of Knowledge, Cab Direct, Science Direct, Google Scholar, eLIBRARY.RU, CyberLeninka, CNKI and VIP. Search terms included Echinococc*, hydatid, epidemiology, logistic regression, risk factors, odds ratio, relative risk, risk factors. Reports, including grey literature where available, that had suitable data were selected and data were extracted. The main pathways of transmission were hypothesised to be contact with the definitive host, contaminated water, contaminated food and contaminated environment (other than food). For each study the attributable fraction for these potential sources of infection was calculated from the data presented. A meta-analysis was then undertaken to obtain pooled estimates for the relative contribution of these transmission pathways.

RESULTS

Data from 28 cross-sectional studies and 14 case-control studies were extracted. There was strong evidence for transmission by direct contact with dogs for both CE and AE. The estimated attributable fractions were 26.1% (CI 13.8%-39.6%) and 34.4% (CI 20.7% -48.2%) respectively. Transmission through contaminated water was estimated to be responsible for approximately 29.4% (CI 12.1%-51.7%) for CE and 24.8% (CI 10.6% to 42.6%) for AE. Contaminated food may be responsible for approximately 23.4% of CE cases (CI 2.1%-47.3%). Globally, there was insufficient evidence to conclude AE can be transmitted by food, although case control studies from low human incidence areas suggested that possibly 32.5% (CI 10.0%-53.2%) could be transmitted by food. There was also insufficient evidence that direct contact with foxes was a significant source of human disease. There were no suitable studies with a risk of environmental contact reported, but the residual attributable fraction thatwould likely include this pathway was approximately 21.1% for CE and 11.1% for AE.

CONCLUSIONS

The results support the hypothesis that dog contact and drinking contaminated water are major pathways of transmission of both CE and AE. For contaminated food, the results are less consistent, but suggest that it is an important transmission pathway and provide better evidence than expert elicitations as previously used.

Toxoplasma gondii infection in slaughtered pigs and cattle in Poland: seroprevalence, molecular detection and characterization of parasites in meat

Background

Toxoplasma gondii infection may pose a severe medical problem especially in a congenital form and as an acquired infection in immunocompromised persons. Raw and undercooked meat of slaughtered animals is regarded as an important source of parasite infection; however, data concerning this issue in Poland are still insufficient. The aim of this study was to estimate the prevalence of T. gondii infection in pigs and cattle slaughtered for human consumption in Poland using serological and molecular methods.

Methods

Sera of 3111 pigs and 2411 cattle from 16 regions (voivodeships) of the country were examined for the presence of anti-T. gondii IgG using the direct agglutination test (DAT). Pepsin-digested samples of diaphragm and heart of seropositive animals were examined for the presence of T. gondii DNA (B1 gene) by nested PCR and real-time PCR, while non-digested samples were only examined by nested PCR. The B1 gene DNA samples were genotyped at 11 genetic markers using multilocus nested PCR-RFLP (Mn-PCR-RFLP) and sequencing.

Results

Seropositive DAT results were found in 11.9% of pigs and 13.0% of cattle. The highest seroprevalence was found in pigs from Podkarpackie (32.6%) and in cattle from Mazowieckie (44.6%). Data analysis showed that cattle > 5–10 years-old, as well as cattle and pigs from small farms, and pigs from farms with open production systems, had higher odds of testing seropositive (P < 0.05). Among the examined tissue samples, positive PCR results were found in samples from 12.2% and 10.2% of seropositive pigs and cattle, respectively. Among the samples successfully genotyped by Mn-PCR-RFLP and sequenced, four samples were identified as T. gondii type II and one sample as type I.

Conclusions

The presence of T. gondii antibodies in a substantial proportion of examined pigs and cattle as well as the detection of parasite DNA in their tissues highlight a potential health risk to the consumers in Poland.

Why we need a European focus on foodborne parasites

Foodborne parasites (FBP) are recognized as being a neglected pathogen group, often associated with marginalized or disadvantaged populations, especially those living in regions where water supply or sanitation are inadequate. Nevertheless, we are also increasingly recognising that FBP are not just restricted to such places, and even those that do have a circumscribed endemic area may also travel further in our globalised world; FBP are relevant everywhere, including Europe. Against this background, COST Action Euro-FBP (FA1408) was established and ran for a period of 4 years, addressing a number of different questions related to FBP, particularly in the European setting. In this special issue (SI), some of the issues and outputs associated with Euro-FBP are considered in greater depth, as an output also of the final Euro-FBP meeting. As well as more general issues regarding, for example, globalization and climate change, use of economic models, and the value of risk-based surveillance that puts the topic in perspective, individual articles are included that address specific parasites. These include protozoan parasites, such as Cryptosporidium, Giardia, and Toxoplasma, as contaminants of water, shellfish, and fresh produce, fishborne parasites such as Anisakid nematodes, and meatborne parasites, such as Trichinella. Some of the works provide specific data on occurrence or outbreaks, whilst others are concerned with techniques. In addition, implementation of some of the educational and collaborative tools that are unique to COST Actions are described. COST Actions are not generally intended to deliver a scientific endpoint, and Euro-FBP does not do so. However, the articles in this SI, along with other articles published elsewhere during and subsequent to the course of the Action, as direct outputs of the Euro-FBP activities, indicate that FBP are indeed a relevant topic for European scientists.

Epidemiology and surveillance of human (neuro)cysticercosis in Europe: is enhanced surveillance required?

OBJECTIVES

To report on relevant national surveillance systems of (N)CC and taeniasis (the infection with the adult tapeworm) in the European Union/European Economic Area and to assess the magnitude of (N)CC occurrence by retrieving information on cases for the period 2000-2016.

METHODS

(N)CC cases were retrieved via national reporting systems, a systematic literature search, contact with clinicians and a search for relevant 'International Statistical Classification of Diseases and Related Health Problems' (ICD)-based data.

RESULTS

Mandatory notification systems for (N)CC were found in Hungary, Iceland and Poland. Ten cases were reported in Poland and none in Hungary and Iceland. Through the systematic literature review and information given by clinicians, 263 individual and 721 aggregated (N)CC cases from 19 European countries were identified. ICD-based data were obtained from five countries. From 2000 to 2016, a total of 3489 cases (N)CC cases were coded: 832 in Italy, eight in Latvia, 357 in Portugal, 2116 in Spain and 176 in Sweden.

CONCLUSION

Despite being classified as a possible eradicable disease, (N)CC is still diagnosed across Europe, yet its true extent and impact remain unclear.

Molecular Detection and Genotyping of Toxoplasma gondii and Neospora caninum in Slaughtered Goats in Central China

Toxoplasma gondii and Neospora caninum infections can cause reproductive failure in animals, including goats, and toxoplasmosis is one of the most important foodborne diseases. However, information on the molecular prevalence and genetic characterization of T. gondii and N. caninum in the tissues of goats in China is limited. In this study, brain samples of 422 slaughtered goats were collected from slaughterhouses in Henan and Anhui provinces, Central China, and examined for the presence of T. gondii and N. caninum by nested polymerase chain reaction (PCR) based on B1 and NC5 genes, respectively. The prevalence of T. gondii and N. caninum DNA was 5.2% and 2.8%, respectively. No significant differences were found between the prevalences of two parasite infections and animal age, sex, and region (p > 0.05). Two of 22 T. gondii-positive samples were completely genotyped at 11 genetic markers (SAG1, [3' + 5'] SAG2, alternative SAG2 [alt. SAG2], SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) using PCR-restriction fragment length polymorphism, and were identified as genotype ToxoDB no. 225, which has not been previously reported in goats in any country worldwide. For N. caninum, two different sequences at the ITS1 region, three genotypes at the MS5 microsatellite locus, and one genotype at the MS8 locus were identified. This study showed that T. gondii and N. caninum are moderately prevalent in goats in Central China; however, it should be emphasized that T. gondii prevalence in goats poses a potential health threat for consumers in the investigated areas. To the best of our knowledge, this is the first report on the genetic characterization of N. caninum isolates from goats in China. Our results have important implications for a better understanding of the genetic diversity of these parasites in China.

Why do we need training? - A "Training school on molecular methods used for foodborne parasite diagnostics in different matrices" is a example of knowledge transfer to foster research quality in EU

Foodborne parasites with zoonotic potential are of particular concern for human health, being responsible for serious and potentially life threatening diseases. In the last decades, the development of molecular biology techniques have been successfully implemented for clinical diagnosis of FBPs in animal or human samples providing cheaper, less labor intensive, reliable and more sensitive tests. It is apparent from recent publications that unsubstantiated molecular methods for parasite detection that have undergone scant evaluation for sensitivity and specificity are becoming increasingly common. The aim of the organized Training Schools was to transfer knowledge on application, optimization and troubleshooting for methods used to extract, amplify, and sequence nucleic acids from contaminated matrices and isolated FBPs. The organized Training Schools fulfilled the trainees' expectations, whom acquired useful knowledge for their research activities.

Anisakis Sensitization in the Croatian fish processing workers: Behavioral instead of occupational risk factors?

We undertook the first study systematically evaluating the risk of Anisakis-sensitization in Croatian fish-processing workers and potential genetic susceptibility to anisakiasis. Anti-Anisakis IgE seroprevalence and risk factors for 600 employees of Croatian fish processing facilities and 466 blood donor controls, were assessed by indirect ELISA targeted with: recombinant Ani s 1 and Ani s 7 allergens, an Anisakis crude extract, the commercial ImmunoCAP kit, and questionnaires. Genetic susceptibility to anisakiasis was evaluated by genotypisation of human leukocytes alleles (HLA). Anti-Anisakis seropositive and a fraction of negative subjects were also assessed by ELISA and Western Blot (WB) for IgG seroprevalence to Trichinella spp. Overall, the observed anti-Anisakis seroprevalence inferred by indirect ELISA was significantly higher in fish processing workers (1.8%, 95% CI 0.9–3.3%) compared to the controls (0%, 0–0.8%). Seven out of 11 Ani s 1 and Ani s 7-positives and none of selected 65 negative sera, tested positive on whole-Anisakis extract (ImmunoCAP), whereas Anisakis crude extract ELISA detected 3.9% (2.4–6.0%) seropositives in fish processing workers, three (14%) of which showed IgE reactivity to milk proteins. The highest risk associated with Anisakis-sensitization among workers was fishing in the free time, rather than any of attributes related to the occupational exposure. Although no association was observed between anti-Anisakis seropositivity and wearing gloves or protective goggles, the majority of workers (92%) wore protective gloves, minimizing the risk for Anisakis sensitization via skin contact. Six HLA alleles within DRB1 gene were significantly associated with seropositivity under dominant, allelic or recessive models. All sera confirmed negative for anti-Trichinella spp. IgG. The study exhaustively covered almost all marine fish processing workers in Croatia, reflecting real-time Anisakis sensitization status within the industry, already under the influence of wide array of allergens.

Anisakiasis is a human disease caused by ingestion of live Anisakis spp. larvae by raw seafood. Fish processing and aquaculture workers (approximately 60 million people world-wide) are at occupational risk of becoming sensitized to Anisakis. This is the first study systematically evaluating the risk of Anisakis-sensitization in Croatian fish-processing workers and potential genetic susceptibility to anisakiasis in the analysed population. Observed seroprevalence was significantly higher in fish processing workers (1.8%) compared to the controls (0%). Surprisingly, the highest risk associated with Anisakis-sensitization among workers was fishing in their free time, rather than any of attributes related to the occupational exposure. While no association was observed between anti-Anisakis seropositivity and wearing gloves or protective goggles, the majority of workers (92%) wore protective gloves, minimizing the risk for Anisakis sensitization via skin contact. Additionally, seroprevalence to another important food-borne helminth, Trichinella spp. assessed in all Anisakis-positive subjects showed to be negative. Almost all marine fish processing workers in Croatia were part of this research, reflecting real-time Anisakis-sensitization status within the industry. This sets a baseline for the future tracking of sensitization in the sector already under the influence of wide array of allergens.

Comparative evaluation of UNEX-based DNA extraction for molecular detection of Cyclospora cayetanensis, Toxoplasma gondii, and Cryptosporidium parvum as contaminants of berries

The potential public health impact of foodborne parasites (FBP) transmitted via contaminated fresh produces indicates the necessity for robust and reliable laboratory methods for their detection and identification on this infection vehicle. Standardization of methods for detection of common FBP in fresh produce is to be expected and ensuring that the DNA extraction approach is most appropriate for the FBP of interest and for the matrix being analyzed is also important. Therefore, the aim of the present study was to compare the efficacy of two commercially available DNA extraction procedures, the UNEX-based method and DNeasy PowerSoil kit in the detection of three protozoan parasites, C. cayetanensis, C. parvum, and T. gondii, on contaminated berries. Oocysts of each parasite were spiked into the pellets of raspberry and blueberry washes. The spiked pellets were then randomly assigned to DNA extraction using either the PowerSoil or UNEX method, with DNA extraction with both methods performed by two independent analysts. The detection rate when berry washes were spiked with 20 oocysts of C. cayetanensis, T. gondii, and C. parvum was 95%, 85%, and 40%, respectively, when using the PowerSoil kit; whereas the equivalent results using the UNEX method were 55%, 60%, and 5%, respectively. In addition, significantly lower C_q values were achieved for each parasite in the samples spiked with 500 oocysts when the PowerSoil kit was used. Possible reasons for these results are discussed, and include the composition of both the beads and the buffers in each method.

Cat-dependent diseases cost Australia AU$6 billion per year through impacts on human health and livestock production

Abstract ContextCats are the definitive or primary host for pathogens that cause diseases in people and livestock. These cat-dependent diseases would not occur in Australia if cats had not been introduced, and their ongoing persistence depends on contacts with cats. Toxoplasma gondii is a protozoan parasite that cycles between cats and any other warm-blooded animals. People infected by T. gondii may appear asymptomatic, or have a mild illness, or experience severe, potentially lethal symptoms; the parasite may also affect behaviour and mental health. T. gondii is also a major contributor to spontaneous abortion in sheep and goats. Two species of Sarcocystis, another genus of protozoan parasite, cycle through cats and sheep, causing macroscopic cysts to form in sheep tissues that reduce meat saleability. Toxocara cati, the cat roundworm, causes minor illnesses in humans and livestock, and the bacterium Bartonella henselae causes cat scratch disease, an infection that can be contracted by people when scratched or bitten by cats carrying the pathogen. AimsWe estimated the economic costs of cat-dependent pathogens in Australia. MethodsWe collated national and global data on infection rates, health and production consequences. Key resultsWe estimated the costs of two cat-dependent diseases (toxoplasmosis, cat scratch disease) in people at AU$6.06 billion (plausible range AU$2.11–10.7 billion) annually, and the costs to livestock production from toxoplasmosis and sarcocystosis at AU$11.7 million (plausible range AU$7.67–18.3 million). Most of the human health costs are due to the associations between T. gondii and higher rates of traffic accidents and mental illness in people. The causality behind these associations remains uncertain, so those costs may be overestimated. Conversely, our estimates are incomplete, infections and illness are under-reported or misdiagnosed, and our understanding of disease outcomes is still imperfect, all of which make our costs underestimated. ConclusionsOur analysis suggests that substantial benefits to public health and livestock production could be realised by reducing exposure to cats and breaking parasite transmission cycles. ImplicationsReducing feral cat populations in farming and urban areas, reducing the pet cat population and increasing rates of pet cat containment could help reduce the burden of cat-dependent diseases to people and livestock.

Surface waters as a potential source of Giardia and Cryptosporidium in Serbia

Giardiasis and cryptosporidiosis are recognized by the WHO as important emerging diseases of the 21st century. Symptoms are similar and include diarrhoea and vomiting, which may be severe, even life-threatening, for the immunocompromised and children under five years of age. Between 2013 and 2017, the Institute for Public Health in Serbia recorded 10 waterborne epidemics that manifested as gastrointestinal disease. Routine testing for enteropathogenic bacteria and viruses did not identify the aetiological agents of these outbreaks. As water is not examined for the presence of protozoa in Serbia, we performed a pilot study to analyse samples from four major rivers and their tributaries using a newly implemented methodology for detection of Giardia and Cryptosporidium, based on the ISO 15553:2006 standard. Using immunofluorescence microscopy, Giardia was detected in 10 out of the 31 samples, Cryptosporidium in five, while two samples were positive for both. Presence of G. duodenalis gDNA was confirmed by amplification of the β-giardin gene in eight samples, of which one and two, respectively, were identified by RFLP as potentially zoonotic assemblages A and B. The results suggest that surface water in Serbia may be a potential source of infection and call for more in-depth studies using sophisticated molecular tools.

In vitro metabolomic footprint of the Echinococcus multilocularis metacestode

Alveolar echinococcosis (AE) is a zoonotic disease that is deadly if left untreated. AE is caused by the larval metacestode stage of the cestode Echinococcus multilocularis. Better knowledge on the host-parasite interface could yield novel targets for improvement of the treatment against AE. We analyzed culture media incubated with in vitro grown E. multilocularis metacestodes by 1H nuclear magnetic resonance spectroscopy to identify the unknown metabolic footprint of the parasite. Moreover, we quantitatively analyzed all amino acids, acetate, glucose, lactate, and succinate in time-course experiments using liquid chromatography and enzymatic assays. The E. multilocularis metacestodes consumed glucose and, surprisingly, threonine and produced succinate, acetate, and alanine as major fermentation products. The metabolic composition of vesicle fluid (VF) from in vitro grown E. multilocularis metacestodes was different from parasite-incubated culture medium with respect to the abundance, but not the spectrum, of metabolites, and some metabolites, in particular amino acids, accumulated in the VF. Overall, this study presents the first characterization of the in vitro metabolic footprint of E. multilocularis metacestodes and VF composition, and it provides the basis for analyses of potentially targetable pathways for future drug development.

Assessment of differences between DNA content of cell-cultured and freely suspended oocysts of Cryptosporidium parvum and their suitability as DNA standards in qPCR

BACKGROUND

Although more modern methods are available, quantitative PCR (qPCR) is reproducible, sensitive and specific with instruments and expertise readily available in many laboratories. As such, the use of qPCR in Cryptosporidium research is well established and still widely used by researchers globally. This method depends upon the generation of standards at different concentrations to generate standard curves subsequently used for the quantification of DNA.

METHODS

We assessed four types of DNA template used to generate standard curves in drug screening studies involving Cryptosporidium spp.: (i) serially diluted Cryptosporidium parvum oocysts (106-1); (ii) diluted template DNA from pure oocysts (×10-×106 dilution of 106 oocyst DNA template); (iii) oocysts incubated in human ileocecal adenocarcinoma (HCT-8) cells (105-1 and 5 × 104-50); and (iv) diluted DNA template (5 × 104) from cell culture incubated parasites (×10-×1000).

RESULTS

Serial dilutions of both cell culture and pure oocyst suspension DNA template yielded better linearity than cell culture derived standards, with dilutions of 106 oocysts exhibiting similar quantification cycle (Cq) values to those obtained from DNA template dilutions of 106 oocysts. In contrast, cell culture incubated oocysts demonstrated significantly higher DNA content than equivalent freely suspended oocysts and diluted DNA template from both cell culture derived and freely suspended oocysts across numerous concentrations.

CONCLUSIONS

For many studies involving Cryptosporidium, only relative DNA content is required and as such, the superior linearity afforded by freely suspended oocysts and diluted DNA template (from either cell culture derived standards or freely suspended oocysts) will allow for more accurate relative quantification in each assay. Parasite division in the cell culture standards likely explains the higher DNA content found. These standards, therefore, have the potential to more accurately reflect DNA content in cell culture assays, and despite more modern methods available for absolute quantification, i.e. droplet digital PCR (ddPCR), the ubiquity of qPCR for the foreseeable future encourages further investigation into the reduced linearity observed in these standards such as varying oocyst seeding density, non-linear growth rates and assay efficiency.

A novel protocol to isolate, detect and differentiate taeniid eggs in leafy greens and berries using real-time PCR with melting curve analysis

BACKGROUND

Zoonotic taeniid cestodes are amongst the most important food-borne parasites affecting human health worldwide. Contamination of fresh produce with the eggs of Echinococcus granulosus (s.l.), Echinococcus multilocularis, and some Taenia species pose a potential food safety risk. However, very few studies have attempted to investigate the potential contamination of fresh produce with taeniid eggs and the available methods are not standardized for this purpose. Established protocols do exist for testing leafy greens and berries for contamination with protozoan parasites and are used in national surveillance programmes. This methodology could be suitable for the detection of taeniids. The objective of this project was to develop and standardize a sensitive and reliable method to detect contamination of leafy greens and berries with eggs of zoonotic taeniids and to differentiate between E. multilocularis, E. granulosus (s.l.) and Taenia spp.

METHODS

We compared the efficacy of different wash solutions to remove Taenia spp. eggs from spiked produce, assessed two DNA extraction kits for their performance on Taenia spp. eggs, and adapted a published conventional multiplex PCR into a real-time PCR with fluorescence melting curve analysis (MCA) that was optimized for use on produce washes. Analytical specificity of this protocol was assessed using non-spiked produce washes as well as a variety of other potentially contaminating parasites.

RESULTS

The protocol as established in this study had an analytical sensitivity of detecting five eggs per spiked sample for both romaine lettuce and strawberries. Unequivocal identification of E. multilocularis, E. granulosus (s.l.) and Taenia spp. was possible through MCA. Amplicon sequencing allowed identification of Taenia to the species level. The real-time PCR also amplified DNA from Dicrocoelium sp., but with a clearly discernable melting curve profile.

CONCLUSION

The new protocol for screening produce for taeniid contamination was highly sensitive. Melting curve analysis and the possibility of amplicon sequencing made this assay very specific. Once further validated, this method could be employed for surveillance of produce for contamination with taeniid parasites to assess potential risks for consumers.

Priorities in research on foodborne parasites indicated by short-term scientific missions as part of COST Action a European Network for Foodborne Parasites (Euro-FBP)

The European Cooperation in Science and Technology (COST) is a funding organization for the creation of research networks. These networks support collaboration and networking among scientists across Europe and thereby give impetus to research advancements and innovation. One of the most important mechanisms of COST actions are the short-term scientific missions (STSM), which are a funding mechanism that enables scientists, particularly those earlier in their careers, to visit an institution or laboratory in another COST Member state in order to learn techniques that will enhance their skills and improve the scientific knowledge of their institution. The European Network for Foodborne Parasites (Euro-FBP; FA1408) was a COST Action that ended in early 2019, which brought together different experts with knowledge and interest on a broad spectrum of different foodborne parasites of relevance in Europe. In the course of the Euro-FBP COST Action, 32 such STSM occurred. This article provides a short overview of the short-term scientific missions that were approved during this action, as well as the relation of these actions to several relevant socio-economic parameters. The subjects of these STSM, the majority of which were concerned with detection techniques, probably reflect the priorities for research skills on foodborne parasites in Europe.

A Simple and Rapid Staining Technique for Sex Determination of Trichinella Larvae Parasites by Confocal Laser Scanning Microscopy

The roundworms of Trichinella genus are worldwide distributed and their prevalence in nature is high. Trichinella genus parasites are the causative agents of foodborne zoonosis trichinellosis. The main prevention and control of the infection are meat inspection by the magnetic stirrer method for the detection of Trichinella larvae in muscle samples. The treatment can be effective if the parasite is discovered early in the intestinal phase. Once the Trichinella larva has reached the muscle tissue, the parasite remains therein and there is no treatment for this life cycle stage. The Trichinella species is dioecious with separate male and female individuals. The developed staining technique that uses confocal laser scanning microscopy (CLSM) displays sufficient results for Trichinella larvae examination and this protocol is applicable to study the internal and external structures and for the sex determination of T. britovi and T. spiralis larvae samples. In the present study, a luminescent derivative was synthesized and used for staining of T. spiralis and T. britovi larvae samples for the examination by CLSM. Various fixatives, such as AFA, 70% ethanol, and Bouin's and Carnoy's solutions were tested for sample preparation. The synthesized luminescent compound demonstrates best visualization results for samples fixed in Bouin's fixative.

Comparative evaluation of loop-mediated isothermal amplification (LAMP) vs qPCR for detection of Toxoplasma gondii oocysts DNA in mussels

The apicomplexan parasite Toxoplasma gondii can infect humans and cause toxoplasmosis. T. gondii has been highly prioritized among the foodborne parasites regarding its global impact on public health. Human infection can occur through multiple routes, including the ingestion of raw or undercooked food contaminated with T. gondii oocysts, such as fresh produce and bivalves. As filter-feeders, bivalves can accumulate and concentrate contaminants, including protozoan (oo)cysts. Although detection of T. gondii in different bivalves by molecular techniques (PCR and qPCR) has been achieved, routine application is currently limited by lack of sensitivity or equipment costs. Here, we describe the assessment of a loop-mediated isothermal amplification (LAMP)-based assay to detect T. gondii oocysts in spiked mussels. Detection limit was down to 5 oocysts/g in tissue and 5 oocyst/ml in hemolymph, and, under the experimental conditions tested, LAMP was found to provide a promising alternative to qPCR.

Editorial overview: From farms and forests to forks? A review of diagnosis and management of globally important zoonotic Echinococcus spp. cestodes

This FAWPAR Special Issue is dedicated to zoonotic Echinococcus species. It is a compilation of invited papers that spans important aspects from molecular markers of emergence, diagnostics in both definitive and intermediate hosts, treatment of human alveolar echinococcosis, to control strategies in definitive hosts.

A novel multiplex real-time PCR for the detection of Echinococcus multilocularis, Toxoplasma gondii, and Cyclospora cayetanensis on berries

Foodborne parasites (FBP) are of major public health importance and warrant appropriate detection and control strategies. Most of the FBP considered for risk-ranking by a panel of experts are potentially transmitted via consumption of contaminated fresh produce, including berries. In this study we focused on the potential of three FBP, namely Echinococcus multilocularis, Toxoplamsa gondii, and Cyclospora cayetanensis, as contaminants of berries. Surveys to assess these parasites as contaminants of fresh produce in general, and berries in particular, are scanty or non-existent mainly due to the lack of optimized laboratory methods for detection. The aim of the present study was to develop and evaluate a novel multiplex qPCR for the simultaneous detection of E. multilocularis, T. gondii, and C. cayetanensis from berry fruits. The efficiency and linearity of each channel in the multiplex qPCR were within the acceptable limits for the range of concentrations tested. Furthermore, the method was shown to have good repeatability (standard deviation ≤0.2 C_q) and intermediate precision (pooled standard deviation of 0.3-0.6 C_q). The limit of detection was estimated to 10 oocysts for Toxoplasma and Cyclospora, and 5 eggs for Echinococcus per 30 g of raspberries or blueberries. In conclusion, evaluation of the present method showed that the newly developed multiplex qPCR is highly specific, precise, and robust method that has potential for application in food-testing laboratories.

Large-scale serological screening of slaughter pigs for Toxoplasma gondii infections in The Netherlands during five years (2012-2016): Trends in seroprevalence over years, seasons, regions and farming systems

•

The seroprevalence of T. gondii in slaughter pigs was between 1.4% and 2.8%.

•

The seroprevalence of T. gondii in slaughter pigs showed a peak in winter.

•

Pigs from organic farms had a higher seroprevalence of T. gondii.

Toxoplasma gondii is the causative agent of the parasitic disease toxoplasmosis, which is an important foodborne zoonosis. Eating undercooked meat of infected animals, including pigs, has been considered the major transmission route of T. gondii to humans. Therefore, it is urgent to develop and implement intervention measures in the pork meat chain to reduce risks of acquiring a T. gondii infection. Proposed measures for control of T. gondii in pigs include serological testing of pigs and audits of pig farms on risk factors for T. gondii infection. So far, these ideas have not been tested in practice. In order to generate knowledge about the epidemiology and seroprevalence of T. gondii, as a basis for developing a surveillance system, we studied the long term seroprevalence over years, farming systems and regions, and seasonal patterns of T. gondii seroprevalence in Dutch slaughter pigs. During a five year study period from 2012 to 2016, serum samples were routinely collected in five Dutch pig slaughterhouses. The sera were tested in an ELISA for the presence of antibodies against Toxoplasma. In total 226,340 serum samples were collected and tested during the study period. The observed seroprevalence varied over years, with the highest overall seroprevalence in 2014 (2.8%) and the lowest in 2016 (1.4%). A higher seroprevalence was observed in pigs from organic farms compared to pigs from conventional farms. The overall risk of infection was on average 2.63 times significantly (p < 0.001) higher for organically raised pigs than for conventionally raised pigs. A seasonal pattern in seroprevalence was observed: the results showed a dominant annual periodicity with a seroprevalence peak in winter around week 1 and a minimum seroprevalence in summer around week 27.

To our knowledge, this is the first large scale study on the seroprevalence of T. gondii in slaughter pigs. In comparison to other European serological studies, the observed seroprevalence seems to be relatively low. However, care is needed when comparing the results with other studies because of differences in test setup, the number of samples and time period of sampling. The results can be used as a starting point for developing a surveillance system for T. gondii, and for implementation of intervention measures.

Foodborne Parasites in Europe: Present Status and Future Trends

Although foodborne parasites (FBPs) are becoming recognized as important foodborne pathogens, they remain neglected compared with bacterial and viral foodborne pathogens. As drivers for infection with FBPs are variable, it is often unclear for funding bodies where research should be prioritized. Through a COST Action (Euro-FBP; FA1408), we harnessed Europe-wide expertise to address these questions, using an Expert Knowledge Elicitation approach. Eating habits, lack of food-chain control, lack of awareness from relevant agencies, globalization, and water quality were identified as major drivers for FBP infection. Prioritized research needs to be largely focused on methodological gaps, but also on surveillance concerns, impact-assessment issues, and the role of microbiota. Despite the European focus, these responses should be relevant to those concerned with FBPs globally.

Toxoplasma gondii in water buffaloes (Bubalus bubalis) from Romania: what is the importance for public health?

The purpose of our study was to evaluate the prevalence of Toxoplasma gondii infection in autochthonous Carpathian buffaloes from northwestern Romania by serology, PCR techniques, and mouse bioassay. Agreement between MAT and ELISA, correlation between indirect and direct detection methods, and risk factors were evaluated. The apparent overall seroprevalence of T. gondii was 8.1% by MAT and 6.6% by ELISA. The agreement between ELISA and MAT was fair. The apparent seroprevalence was significantly higher in adult buffaloes (12.5%) compared to calves (0.0%) and juveniles (1.9%) by MAT. Most of the positive adult buffaloes detected by MAT had antibodies at a low sera dilution and the highest dilution was 1:768 in a juvenile female (30 months). No viable T. gondii was detected by mouse bioassay, as no T. gondii cyst or DNA was found in the brain of mice and they did not seroconvert. However, T. gondii DNA was detected in two buffaloes: in a 30-month-old male buffalo by qPCR on the diaphragm digest and in a 252-month-old female buffalo by RE nPCR on the mesenteric lymph node. Both animals were negative in MAT and ELISA. The total prevalence of T. gondii by direct detection methods was 2.7%. There was no correlation between indirect and direct detection methods. Since no viable T. gondii was detected in buffaloes, the risk of human infection from buffalo meat is minimal. Buffaloes' biological response to a T. gondii infection appears to be very similar to the response of cattle.