Berries as a potential transmission vehicle for taeniid eggs

Vaccinium uliginosum L. (bog bilberry) and the search for its alleged toxicity: a review

Bog bilberry (Vaccinium uliginosum L.) is a wild-growing berry native to all circumboreal regions. There is however a significant discrepancy in the uses of bog bilberry fruits around the world. There exists a strong prejudice against the use of these berries in many European countries as well as a few incidences of poisoning reported between 1906 and 1944. In Asia and North America, this fear is completely absent from the local knowledge and the bog bilberry is valued as an excellent food and medicinal plant. There has been a lack of research on the topic in the last 50 years and thus the presumed toxicity remains unproven. This review aims to gather the conflicting information from all regions where bog bilberry grows and present them in a critical way to elucidate the possible explanations for the discrepancies. There are several possible explanations for the alleged toxicity of the bog bilberry, including a fungal infection of the fruits, individual intolerance or accidental poisoning by a different plant species; the local names meaning "drunk, inebriating, vomit-inducing berry" may be related to the alcoholic drinks made from them. This review highlights the gap in knowledge and serves as a theoretical framework for future research.

First report demonstrating the presence of Toxocara spp. eggs on vegetables grown in community gardens in Europe

Toxocara canis and T. cati are zoonotic roundworm parasites of dogs, cats and foxes. These definitive hosts pass eggs in their faeces, which contaminate the environment and can subsequently be ingested via soil or contaminated vegetables. In humans, infection with Toxocara can have serious health implications. This proof-of-concept study aimed to investigate the presence of Toxocara spp. eggs on ‘ready-to-eat’ vegetables (lettuce, spinach, spring onion and celery) sampled from community gardens in southern England. The contamination of vegetables with Toxocara eggs has never been investigated in the UK before, and more widely, this is the first time vegetables grown in community gardens in Europe have been assessed for Toxocara egg contamination. Sixteen community gardens participated in the study, providing 82 vegetable samples fit for analysis. Study participants also completed an anonymous questionnaire on observed visits to the sites by definitive hosts of Toxocara. Comparison of egg recovery methods was performed using lettuce samples spiked with a series of Toxocara spp. egg concentrations, with sedimentation and centrifugal concentration retrieving the highest number of eggs. A sample (100 g) of each vegetable type obtained from participating community gardens was tested for the presence of Toxocara eggs using the optimised method. Two lettuce samples tested positive for Toxocara spp. eggs, giving a prevalence of 2.4% (95% CI =1.3–3.5%) for vegetable samples overall, and 6.5% (95% CI = 4.7–8.3%; n = 31) specifically for lettuce. Questionnaire data revealed that foxes, cats and dogs frequently visited the community gardens in the study, with 88% (68/77) of respondents reporting seeing a definitive host species or the faeces of a definitive host at their site. This proof-of-concept study showed for the first time the presence of Toxocara spp. eggs on vegetables grown in the UK, as well as within the soil where these vegetables originated, and highlights biosecurity and zoonotic risks in community gardens. This study establishes a method for assessment of Toxocara spp. eggs on vegetable produce and paves the way for larger-scale investigations of Toxocara spp. egg contamination on field-grown vegetables.

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First report of Toxocara eggs on vegetables grown in community gardens in Europe.

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Toxocara also detected in the soil where these vegetables originated.

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Definitive hosts for Toxocara canis and T. cati frequently visit community gardens.

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Sedimentation method recovered the most Toxocara eggs from spiked lettuce samples.

Dispersal of taeniid eggs: Experimental faecal contamination of forest environment followed by DNA detection in wild berries

To understand Taeniidae epidemiology, the principles of egg-dispersion dynamics under natural conditions must be known. In this study, non-zoonotic Taenia laticollis was used as a model parasite for the family Taeniidae (including Echinococcus spp.). An experiment to investigate dispersion from contaminated faeces to the surroundings was performed both with bilberries (Vaccinium myrtillus) and lingonberries (Vaccinium vitis-idaea), both of which are commercially harvested wild berries in Finland. For this experiment, 30 g of fox faeces was inoculated with 30,000 T. laticollis eggs for the bilberry experiment and 100,000 eggs for the lingonberry experiment. The faecal material was placed in the middle of good berry growth areas in four locations for bilberries and eight locations for lingonberries. After 41–42 days, berries at different distances (0–15 m) from the original contamination spot were collected and delivered to our laboratory. DNA was extracted from washed and sieved material and analysed using T. laticollis-specific semi-quantitative SYBR Green real-time polymerase chain reaction (qPCR). Taenia laticollis-specific DNA was recovered from 67% (8/12) of bilberry samples but not reliably from any of the lingonberry samples 0% (0/24), although the exposure dose was higher for those. The qPCR results suggest that under natural conditions, taeniid egg dispersion from the contamination spot is demonstrated but attachment is berry specific. The surface of bilberries may be more adhesive for taeniid eggs than the waxier and harder pericarp of the lingonberries or there might be a difference in the dispersal mechanism caused by different biotopes.

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Experimental dispersal of non-zoonotic taeniid eggs was used as a model for pathogenic Taeniidae as Echinococcus spp.

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Taeniid DNA was detected from wild bilberries under natural conditions after over a month from different distances.

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Parasitic egg dispersal was evident to bilberries but not to the lingonberries.

Diagnostic tools for the detection of taeniid eggs in different environmental matrices: A systematic review

The cestode family Taeniidae consists of the genera Echinococcus and Taenia, both of which include zoonotic tapeworms of serious public health importance. Various environmental matrices have been identified from which parasite transmission to animals and humans can occur, and many techniques for detecting taeniid eggs in different environments have been developed. However, the majority lack appropriate validation, and standardized egg isolation procedures are absent. This hampers interstudy comparisons and poses a challenge for future researchers when deciding which technique to implement for assessing taeniid egg contamination in a particular matrix. Therefore, the aim of this systematic review was to present an overview of the detection methods for taeniid eggs in the environment, to discuss and compare them, and to provide recommendations for future studies. In total, 1814 publications were retrieved from scientific databases, and, ultimately, data were systematically reviewed from 90 papers. The results provide an overview of numerous diagnostic tests for taeniid egg detection in (or on) water, food, soil, insects, objects, and air. These tools could be categorized as either conventional (light microscopy), molecular, or immunodetection tools. The relatively cheap microscopy techniques often lack sensitivity and are unable to identify a taeniid egg at the genus level. Nevertheless, several records ascribed a genus, or even species, to taeniid eggs that had been detected by light microscopy. Molecular and immunodetection tools offer better specificity, but still rely on the preceding egg recovery steps that also affect overall sensitivity. Finally, the majority of the methods lacked any attempt at performance evaluation and standardization, especially at the earlier stages of the analysis (e.g., sampling strategy, storage conditions, egg recovery), and viability was rarely addressed. As such, our review highlights the need for standardized, validated detection tools, that not only assess the extent of environmental contamination, but also the egg genus or species, and address viability.

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The cestode family Taeniidae contains species of serious public health importance.

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Parasite transmission may occur from several environmental matrices.

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Many methods for environmental detection of taeniid eggs have been developed.

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These often lack standardization, performance evaluation, and viability assessment.

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.

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.

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.

A new SYBR green real-time PCR assay for semi-quantitative detection of Echinococcus multilocularis and Echinococcus canadensis DNA on bilberries (Vaccinium myrtillus)

Berries and vegetables are potential transmission vehicles for eggs of pathogenic parasites, such as Echinococcus spp. We developed a SYBR Green based semi-quantitative real-time PCR (qPCR) method for detection of Echinococcus multilocularis and Echinococcus canadensis DNA from berry samples. A set of primers based on the mitochondrial NADH dehydrogenase subunit 1 (nad1) gene was designed and evaluated. To assess the efficacy of the assay, we spiked bilberries (Vaccinium myrtillus) with a known amount of E. multilocularis eggs. The detection limit for the assay using the NAD1_88 primer set was 4.37 × 10-5 ng/μl of E. multilocularis DNA. Under artificial contamination of berries, 50 E. multilocularis eggs were reliably detected in 250 g of bilberries. Analytical sensitivity of the assay was determined to be 100% with three eggs. As an application of the assay, 21 bilberry samples from Finnish market places and 21 bilberry samples from Estonia were examined. Previously described sieving and DNA extraction methods were used, and the samples were analyzed for E. multilocularis and E. canadensis DNA using semi-quantitative real-time PCR and a melting curve analysis of the amplified products. Echinococcus DNA was not detected in any of the commercial berry samples. This easy and fast method can be used for an efficient detection of E. multilocularis and E. canadensis in bilberries or other berries, and it is applicable also for fruits and vegetables.