Keeping it cool: Survival of Giardia cysts and Cryptosporidium oocysts on lettuce leaves

Establishing the performance of next generation amplicon sequencing for detection of Giardia duodenalis in ready-to-eat packaged leafy greens

Giardia duodenalis is a globally distributed intestinal parasite that commonly infects both humans and animals. G. duodenalis is a species complex, which includes eight assemblages that vary both in genetic structure and host specificity. The prevalence of mixed-assemblage G. duodenalis cysts on food, an understudied infection route for G. duodenalis, remains unknown. In the present study, a method able to detect G. duodenalis mixed-assemblage infections using next generation amplicon sequencing (NGS) of the beta-giardin gene was applied in combination with the US-FDA's BAM Chapter 19b protocol for detection of G. duodenalis from fresh produce to ascertain the limit of detection of G. duodenalis on leafy greens. Ready-to-eat baby Romaine lettuce was inoculated with 5 (n=5), 20 (n=10), 100 (n=10), 200 (n=10), or 1000 (n=10) G. duodenalis cysts of the assemblage B strain H3. Detection of G. duodenalis was successful in 100% of the samples seeded with 1000, 200, and 100 cysts, in 50% of the samples seeded with 20 cysts, and in none of the samples seeded with 5 cysts. We thus demonstrate robust detection of G. duodenalis on packaged leafy greens using the BAM Chapter 19B method coupled with assemblage-sensitive NGS. This protocol provides a new diagnostic tool useful for both prevalence studies and outbreak investigations involving fresh produce that may assist in better describing the role of G. duodenalis in foodborne illness and in protecting consumers from contaminated fresh produce.

Cryptosporidium spp. in large-scale sheep farms in China: prevalence and genetic diversity

Cryptosporidium spp. are significant zoonotic intestinal parasites that induce diarrhea and even death across most vertebrates, including humans. Previous studies showed that sheep are important hosts for Cryptosporidium and that its distribution in sheep is influenced by geography, feeding patterns, age, and season. Environmental factors also influence the transmission of Cryptosporidium. Molecular studies of Cryptosporidium in sheep have been conducted in only a few regions of China, and studies into the effect of sheep-housing environments on Cryptosporidium transmission are even rarer. To detect the prevalence of Cryptosporidium in large-scale sheep-housing farms, a total of 1241 fecal samples were collected from sheep, 727 environmental samples were taken from sheep housing, and 30 water samples were collected in six regions of China. To ascertain the existence of the parasite and identify the species of Cryptosporidium spp., we conducted nested PCR amplification of DNA extracted from all samples using the small-subunit (SSU) rRNA gene as a target. For a more in-depth analysis of Cryptosporidium spp. subtypes, C. xiaoi-and C. ubiquitum-positive samples underwent separate nested PCR amplification targeting the 60 kDa glycoprotein (gp60) gene. The amplification of the Cryptosporidium spp. SSU rRNA gene locus from the whole genomic DNA of all samples yielded a positive rate of 1.2% (20/1241) in fecal samples, 0.1% (1/727) in environmental samples, and no positive samples were found in water samples. The prevalence of Cryptosporidium spp. infection in large-scale housed sheep was 1.7%, which was higher than that in free-ranging sheep (0.0%). The highest prevalence of infection was found in weaning lambs (6.8%). Among the different seasons, the peaks were found in the fall and winter. The most prevalent species were C. xiaoi and C. ubiquitum, with the former accounting for the majority of infections. The distribution of C. xiaoi subtypes was diverse, with XXIIIc (n = 1), XXIIId (n = 2), XXIIIe (n = 2), and XXIIIl (n = 4) identified. In contrast, only one subtype, XIIa (n = 9), was found in C. ubiquitum. In this study, C. xiaoi and C. ubiquitum were found to be the predominant species, and Cryptosporidium was found to be present in the environment. These findings provide an important foundation for the comprehensive prevention and management of Cryptosporidium in intensively reared sheep. Furthermore, by elucidating the prevalence of Cryptosporidium in sheep and its potential role in environmental transmission, this study deepens our understanding of the intricate interactions between animal health, environmental contamination, and public health dynamics.

Parasitic Contamination of Fresh Leafy Green Vegetables Sold in Northern Lebanon

Contaminated, raw or undercooked vegetables can transmit parasitic infections. Here, we investigated parasitic contamination of leafy green vegetables sold in local markets in the Tripoli district, Lebanon, during two consecutive autumn seasons (2020-2021). The study involved the microscopic examination of 300 samples of five different types of vegetables (60 samples per type) and used standardized qualitative parasitological techniques for some protozoa and helminths. The results showed that 16.7% (95% interval for p: 12.6%, 21.4%) (50/300) of the vegetable samples were contaminated with at least one parasite. The most frequently detected parasite was Blastocystis spp. (8.7%; 26/300); this was followed in frequency by Ascaris spp. (3.7%; 11/300). Among the different vegetable types, lettuce (23.3%; 14/60) was the most contaminated, while arugula was the least contaminated (11.7%; 7/60). The statistical analysis did not reveal any significant association between the prevalence of parasitic contamination and the investigated risk factors, which included collection date, vegetable type, market storage status, and wetness of vegetables at the time of purchase (p > 0.05). The high prevalence of parasitic contamination also suggested the potential presence of other microbial pathogens. These findings are important because leafy green vegetables are preferentially and heavily consumed raw in Lebanon. Thus, implementing effective measures that target the farm-to-fork continuum is recommended in order to reduce the spread of intestinal pathogens.

Molecular Detection and Epidemiology of Potentially Zoonotic Cryptosporidium spp. and Giardia duodenalis in Wild Boar (Sus scrofa) from Eastern Spain

The protozoans Giardia duodenalis and Cryptosporidium spp. are common causes of gastrointestinal disease in humans and animals. While both are commonly documented in domestic animals, few studies have analysed their presence in wildlife. To assess the prevalence of both parasites in wild boar (Sus scrofa) in the Valencian Community (eastern Spain), 498 wild boar faecal samples were collected from 2018 to 2022. Cryptosporidium spp. was detected by performing a nested PCR targeting a 578 bp sequence of the small subunit ribosomal RNA gene (SSU rRNA), followed by sequencing and phylogenetic analysis. For G. duodenalis, a qPCR amplifying a fragment of 62 bp from the SSU rRNA was employed. Positive samples were genotyped for glutamate dehydrogenase and β-giardin genes. Different epidemiological factors were considered potential modulating variables in the transmission of both parasites. G. duodenalis prevalence was 1.20%, while Cryptosporidium spp. prevalence reached 21.7%. Coinfection was observed in 0.2%. Genotyping of G. duodenalis isolates only detected genotype E. Two species of Cryptosporidium spp. were identified: Cryptosporidium scrofarum and Cryptosporidium suis. The results of this study demonstrate that the exposure to Cryptosporidium spp. in wild boars is high, particularly among young individuals belonging to the Typical Mediterranean climate. Moreover, the probability of infection is dependent on both the season and the density of wild boars. On the other side, exposure to G. duodenalis seems scarce and is influenced, in turn, by the climate. Both Cryptosporidium species detected in the present study have been reported in humans. Due to wild boar increasing in number and their colonisation of urban and peri-urban areas, this could represent an inherent health risk for the human population.

Persistence and survival of Cryptosporidium parvum oocysts on lamb's lettuce leaves during plant growth and in washing conditions of minimally-processed salads

Cryptosporidium is the causative agent of cryptosporidiosis, which results, among others, in profuse diarrhoea. Transmission to humans occurs via the faecal-oral route directly by contact with infected hosts or indirectly by waterborne or foodborne routes. For the latter, parasite transmission is closely linked to the oocyst's ability to persist and survive in food matrices. In this study, we evaluated the persistence and survival of Cryptosporidium oocysts in lamb's lettuce: i) during plant growth and ii) in conditions mimicking the industrial washing process applied in minimally-processed vegetables (MPV). Results show that oocysts persisted during the growth of lamb's lettuce, i.e. two months from the 2-leaf stage until the 8-leaf harvest time (-0.89 Log10 of oocysts). However, their survival decreased from as early as one week (-0.61 Log10), and only 6 % of oocysts remained infective at the time of harvest. The washing process had a limited effect on parasite load (<0.5 Log10) and no effect on survival; chlorination of washing water did not improve the efficiency (removal and inactivation) of the process. The ability of C. parvum to persist and survive throughout the food chain may drive its transmission to humans through MPV products. Appropriate management measures should be implemented at each operational level to limit contamination and ensure food safety of fresh produce.

Influence of Selected Factors on the Survival Assessment and Detection of Giardia intestinalis DNA in Axenic Culture

Giardia intestinalis is one of the most common food-borne protozoa. The sensitivity of pathogens to physical and chemical factors is the basis for developing measures to reduce the incidence of the population. Several methods are available to detect the presence of G. intestinalis. The study determines the influence of 22 selected factors on the survival assessment and detection of G. intestinalis DNA in trophozoites axenically cultured. The influence of a given factor on the test result was observed in the case of 17 factors (77.3%) in the microscopic method, while only in the case of 3 (13.6%) substances in the real-time PCR method. Prevention of G. intestinalis infections, e.g., by ensuring food and water safety, is a crucial issue affecting public health. The experiment was conducted on trophozoites as the first approach. It is necessary to continue research and observe the epidemiological situation. In future studies, the impact of the studied factors on the survival assessment and detection of Giardia intestinalis DNA in axenically cultured cysts should be determined.

Protozoa as the “Underdogs” for Microbiological Quality Evaluation of Fresh Vegetables

The monitoring of the microbial quality of fresh products in the industrial environment has mainly focused on bacterial indicators. Protozoa, such as Giardia duodenalis, Cryptosporidium spp., Toxoplasma gondii, and Cyclospora cayetanensis, are routinely excluded from detection and surveillance systems, despite guidelines and regulations that support the need for tracking and monitoring these pathogens in fresh food products. Previous studies performed by our laboratory, within the scope of the SafeConsume project, clearly indicated that consumption of fresh produce may be a source of T. gondii, thus posing a risk for the contraction of toxoplasmosis for susceptible consumers. Therefore, preliminary work was performed in order to assess the microbiological quality of vegetables, highlighting not only bacteria (Escherichia. coli, Listeria monocytogenes, and Salmonella spp.), but also the zoonotic protozoa G. duodenalis and Cryptosporidium spp. Although all samples were found to be acceptable based on bacteriological parameters, cysts of G. duodenalis and oocysts of Cryptosporidium spp. were observed in vegetables. Moreover, it was possible to genetically characterize G. duodenalis positive samples as assemblage A, a genotype that poses risks to human health. Although these are preliminary results, they highlight the need to include protozoa in the microbiological criteria for foodstuffs, as required by EU Law No. 1441/2007, and to improve inactivation and removal procedures of (oo)cysts in fresh produce and water.

Cryptosporidium and Giardia in Biogas Wastewater: Management of Manure Livestock and Hygiene Aspects Using Influent, Effluent, Sewage Canal Samples, Vegetable, and Soil Samples

Cryptosporidium and Giardia are two water- and foodborne protozoan parasites that can cause diarrheal diseases. Poor microbial quality, sanitation conditions, and hygiene practices at exposure to biogas wastewater are important risk factors for human and animal infection. This study highlights the presence and level of both parasites in the environment in relation to biogas waste reuse in Vietnam. A total of 239 samples were collected from different types of samples in the studied districts in Bac Giang province in 2020 via direct immunofluorescent detection to study the occurrence of Cryptosporidium spp. and Giardia spp. (oo)cysts. Among the samples, Cryptosporidium was found in 19 (7.9%) with concentration from 1.104 to 3.105 oocysts/100 mL, while Giardia in 40 (16.7%) with concentration from 1.104 to 2.106 cysts/100 mL, respectively. In detail, the results show that the percentages of positive detection of Cryptosporidium spp. and Giardia spp. in influent, effluent, sewage canal, and vegetables were 13.1% (11/84), 6.0% (5/83), 15.4% (2/13) and 5.9% (1/17) and 26.2% (22/84), 7.2% (6/83), 7.7% (1/13) and 5.9% (1/17), respectively. The results show a trend of decreasing Cryptosporidium and Giardia densities, without statistical significance. Although these parasites decreased after biogas treatment, the remaining loads observed in biogas effluent can reach the watercourses and soil receiving it. Further investigations are needed to contribute to a general understanding of the risk of protozoan parasites, as well as strategies to control and reduce the contamination of environmental water sources and plants and reduce the burden of the pathogens in biogas wastewater in Vietnam.

Cryptosporidium and Giardia in Livestock in Tigray, Northern Ethiopia and Associated Risk Factors for Infection: A Cross-Sectional Study

The occurrence and species/genotypes of Cryptosporidium and Giardia duodenalis infecting young livestock in selected districts of Tigray, Ethiopia were investigated, along with risks associated with infection. A total of 757 faecal samples were collected from calves, lambs, and goat kids from four rural districts in Tigray, and also from calves in periurban Mekelle, Tigray's main city, and analysed for Cryptosporidium oocysts and Giardia cysts. Farmers answered questionnaires regarding potential risk factors at sample collection. Immunofluorescent antibody staining was used for parasite detection, and PCR at selected genes and sequencing of positive samples was used for molecular characterisation. The occurrence of Cryptosporidium infection was 10, 9, and 4% in calves, lambs, and goat kids, respectively; equivalent figures for Giardia infection were 39, 32, and 21%. Molecular characterisation of Cryptosporidium isolates revealed C. ubiquitum, subtype XIIa in all three host species; C. ryanae in calves and goat kids; C. andersoni and C. bovis were identified only in calves, and C. xiaoi was identified in lambs. For Giardia, Assemblage E predominated in all host species, but among calf isolates we also identified a few potentially zoonotic genotypes (assemblages A (AI) and Assemblage B). Periparturient care was shown to be a particularly relevant risk factor for infection, and infections were less likely to occur under extensive management systems. Our major findings were widespread occurrence of both parasites in livestock, and the apparent lack of the most common zoonotic species. Our results are discussed in relation to other relevant studies. As our study was conducted in Tigray, further investigation in different settings in Ethiopia could provide relevant information on transmission and zoonotic potential. In addition, given the dependency on healthy animals for the livelihoods of the population of Tigray, investigation of the effect of these common parasites on livestock productivity is important.

Soil contamination by Echinococcus multilocularis in rural and urban vegetable gardens in relation to fox, cat and dog faecal deposits

Echinococcus multilocularis eggs are deposited on the ground with the faeces of the carnivore definitive hosts. A reliable assessment of the spatial distribution of E. multilocularis eggs in environments used by humans is crucial for the prevention of alveolar echinococcosis (AE). This study was conducted in 192 rural and 71 urban vegetable gardens in AE endemic areas of north-eastern France. Its objective was to explore the relationship between the spatial distribution of E. multilocularis estimated from the collection and molecular analysis of two types of samples: faeces and soil. A total of 1024 carnivore faeces and 463 soil samples were collected and analysed by real-time PCR. No fox droppings and no positive soil samples were collected from the urban gardens. Positive soil samples, positive carnivore faeces, or both, were found in 42%, 24% and 6% of the sampled rural gardens, respectively. No significant association was found between the detection of E. multilocularis in soil samples collected from 50 gardens during a single sampling session and the extent and frequency of deposits of fox and cat faeces collected during repeated sampling sessions conducted in the previous months. In 19/50 gardens, E. multilocularis was detected in the soil while no positive faeces had been collected in the previous 12 months. Conversely, in 8/50 gardens, no soil samples were positive although positive faeces had been collected in the previous months. Collecting and analysing faeces provide information on soil contamination at a given time, while analysing soil samples provides an overview of long-term contamination.

Is Fresh Produce in Tigray, Ethiopia a Potential Transmission Vehicle for Cryptosporidium and Giardia?

In rural Ethiopia, where people often share their homes with their livestock, infections of humans and animals with Cryptosporidium and Giardia are relatively common. One possible transmission route is consumption of contaminated fresh produce; this study investigated the occurrence of Cryptosporidium and Giardia in fresh produce in four districts of rural Tigray in Ethiopia. Fresh produce samples (n = 55) were analysed using standard laboratory procedures. Overall, 15% (8/55) of samples were found to be contaminated. Although contamination levels were mostly low, a few samples had high numbers of Giardia cysts (up to around 70 cysts per 30 g sample). Molecular analyses were largely unsuccessful, but Giardia Assemblage A was identified in one sample. Contamination with these parasites was identified in two of the four districts, but, although a similar pattern has already been described for water contamination, this may be at least partially explained by sampling bias. Nevertheless, we speculate that access to clean water sources may be an important factor for reducing the occurrence of these pathogens. Given the public health and veterinary burden associated with both parasites, the factors which are of importance for their circulation in the communities and environments deserve further investigation.

Optimization and validation of a loop-mediated isothermal amplification (LAMP) assay for detection of Giardia duodenalis in leafy greens

Giardia duodenalis is one of the most common food and water-borne intestinal parasites of humans and animals worldwide. Fresh, ready-to-eat produce such as leafy greens and salad mixes are considered potential transmission vehicles for Giardia infection in humans. Therefore, a specific, sensitive, and reliable method for Giardia detection in leafy greens is needed. We optimized washing procedures for the recovery of Giardia cysts from leafy greens and adapted and validated an existing EF1α LAMP assay for the detection of Giardia DNA to support routine diagnostic surveillance and disease outbreak investigations. Four leafy green types (35 ± 1 g) were spiked with 100 Giardia cysts and we compared washing by shaking with 1 M glycine (n = 20) or 0.1% Alconox (n = 20). DNA was extracted from washes, tested by LAMP and melt curve analysis, and time to positive (TTP) values compared. The detection limit was determined by spiking 10 (n = 40) Giardia cysts onto these same types of leafy greens and processing as above with 0.1% Alconox. Method robustness was assessed by subjecting spring mix (n = 45 total) to aging (1, 3 or 7 days) and washes to aging and freezing conditions prior to testing. Assay repeatability and specificity were evaluated, and an artificial positive control (APC) distinguishable by melt temperature (Tm) from DNA of Giardia spiked on leafy greens was designed to rule out cross-contamination from the control. Giardia detection rates were higher and TTP was lower (P < 0.05) for 0.1% Alconox (19/20, 8.85 ± 0.3 min) compared with 1 M glycine (15/20, 14.53 ± 7.2 min). The LAMP assay detected 10 Giardia cysts spiked on leafy greens in 13–34 min in 14/40 samples tested. Robustness assessment showed that TTP was higher (P < 0.0001) when spiked produce was stored for 7 days (13.09 ± 1.14 min) compared to fresh (9.72 ± 0.43 min). No unspiked samples were positive by LAMP, and the Tm for DNA of Giardia spiked on leafy greens was higher (P < 0.0001, 87.43 ± 0.05 °C) than the APC (86.43 ± 0.12 °C). Within-assay repeatability co-efficient of variation (CV) for TTP was 5.4% and no cross-contamination occurred when spiked and un-spiked samples were processed in alternate order. The optimized sample processing procedure combined with the EF1α LAMP assay is a sensitive, specific, labour-saving, and rapid method for the detection of Giardia cysts in leafy greens.

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We adapted and validated EF1α LAMP assay for detection of Giardia in leafy greens.

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Giardia LAMP is sensitive, specific and has a faster turnaround time than nPCR.

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The assay performs well on aged and deteriorated produce samples.

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Giardia LAMP has been implemented in our lab for routine surveillance testing.

Removal of Parasite Transmission Stages from Berries Using Washing Procedures Suitable for Consumers

Due to the delicate nature of berries and the reduced shelf-life once washed, producers usually do not wash berries. Therefore, consumers are expected to wash the berries prior to consumption, and this might be a more effective way of infection prevention. However, the efficacy of consumer berry-washing procedures in removing the parasite contaminants from the berries surface has not been investigated. The aim of the present study was, therefore, to compare the efficacy of three different washing techniques in removing parasite contaminants. Three alternatives to washing berries before consumption were compared on berries artificially contaminated with oo/cysts of Cyclospora cayetanensis, Cryptosporidium parvum, and Giardia duodenalis. The results show that simple washing of berries under the cold tap for 1 min could remove on average at least 80% of the parasites, except for C. cayetanensis, which seems to be stickier than both G. duodenalis and C. parvum. The percent removal was slightly lower for raspberries as compared to blueberries. Although the differences are expected, a relevant result of the study is that washing contaminated berries prior to consumption by the consumer removes a considerable proportion of parasites and thereby lowers the risk of ingesting parasites’ transmission stages.

Prevalence of Cryptosporidium and Giardia in vegetables in Iran: a nineteen-years meta-analysis review

Cryptosporidium and Giardia are two major protozoa reported from vegetables and environment. The prevalence of these parasites supposes to be different regarding the climate zones. This review aimed to evaluate the prevalence of Cryptosporidium and Giardia in vegetables according to the major climate zones in Iran. The results showed pooled prevalence 7% (95% CI: 2%, 14%) and 4% (95% CI: 3%, 6%) for Cryptosporidium spp., and Giardia spp., respectively. The prevalence of Giardia spp. in mountain, desert and semi-desert, and Mediterranean regions was 4% (95% CI: 2%, 6%), 5% (95% CI: 3%, 8%) and 7% (95% CI: 1%, 18%), respectively. Cryptosporidium spp. was reported 8% (95% CI: 0%, 65%), 6% (95% CI: 0%, 18%) and 4% (95% CI: 0%, 77%) from mountain, desert and semi-desert, and Mediterranean climate zones, respectively. This review suggests the higher prevalence of Giardia and Cryptosporidium in Mediterranean and mountain regions, respectively.

Prevalence and molecular characterization of Giardia duodenalis in dogs in Israel

Three hundred and two stool samples were collected from municipal shelters and owned dogs in different geographical locations in Israel from December 2016 to September 2017 and examined for Giardia and assemblage type by PCR targeting the 18S rRNA and β-giardin genes. Overall Giardia prevalence was 24.5 % (74/30). Giardia prevalence was 1.9-fold higher in dogs ≤ 6 months old compared to > 6 ≤ 12 months old and older dogs [25/61 (41 %), 18/73 (24.6 %) and 31/166 (18.7 %), respectively, (p = 0.001)], 2.3-fold higher in winter [32/90 (35.5 %)] compared to its prevalence during autumn [15/60 (25 %)], spring [10/62 (16.1 %)] and summer [17/89 (19.1 %), p = 0.003)], and 2.7-fold more frequent among diarrheic dogs [23/43 (53.4 %)] compared to those with formed stools [51/253 (20.1 %)], (p = 0.001)]. The Giardia sp. assemblages detected were C and D. Higher infection rates in young, diarrheic dogs, sampled during winter, and housed in municipal shelters, indicates the need for targeted preventive measures.

Food and waterborne protozoan parasites: The African perspective

Parasitic food-borne diseases, particularly those caused by the protozoan parasites Cryptosporidium, Giardia, Cyclospora cayetanensis and Entamoeba are increasingly becoming common and have received considerable attention in the last two decades. The ability of the transmission stages of the parasites to survive in the environment for prolonged periods, globalization of the food industry and changes in eating habits have contributed to the numbers of human infections. This systematic scoping review highlights these important water- and foodborne parasites in the African context, detailing the burden in African water sources, wastewater/effluents and fresh produce. A scoping review search targeting African countries was conducted in Medline, Web of science and African journals online as well as back referencing from included studies covering the period 1990 to January 2020. Out of 1134 studies, 68 were included in the review. The articles covered 17 out of 54 African countries. There were 39/68 studies reporting on water sources while the rest reported on fresh produce. Cryptosporidium prevalence ranged from 6 to 100% in surface water, 4 to 100% in tap water and up to 100% in wastewater and sludge. In fresh produce, Cryptosporidium was reported from five countries with prevalence of 0.8-75%. Giardia was reported in 47 out of 68 articles; prevalence ranged from 2.4% in surface water; 1% to over 70% in tap water; 28-100% in wastewater and 2% - 99% in fresh produce. Prevalence of Cyclospora cayetanensis was lower. Prevalence of Entamoeba was 78% in surface water; 100% in wastewater and up to 99% in fresh produce. This study finds that Africa is no exception to the risk presented by the subject parasites from water and/or food sources. Routine screening for these parasites particularly at household level and provision of adequate and safe drinking water would help to control the parasites.

Comparative Pathobiology of the Intestinal Protozoan Parasites Giardia lamblia, Entamoeba histolytica, and Cryptosporidium parvum

Protozoan parasites can infect the human intestinal tract causing serious diseases. In the following article, we focused on the three most prominent intestinal protozoan pathogens, namely, Giardia lamblia, Entamoeba histolytica, and Cryptosporidium parvum. Both C. parvum and G. lamblia colonize the duodenum, jejunum, and ileum and are the most common causative agents of persistent diarrhea (i.e., cryptosporidiosis and giardiasis). Entamoeba histolytica colonizes the colon and, unlike the two former pathogens, may invade the colon wall and disseminate to other organs, mainly the liver, thereby causing life-threatening amebiasis. Here, we present condensed information concerning the pathobiology of these three diseases.

Public health risks associated with food-borne parasites

Parasites are important food‐borne pathogens. Their complex lifecycles, varied transmission routes, and prolonged periods between infection and symptoms mean that the public health burden and relative importance of different transmission routes are often difficult to assess. Furthermore, there are challenges in detection and diagnostics, and variations in reporting. A Europe‐focused ranking exercise, using multicriteria decision analysis, identified potentially food‐borne parasites of importance, and that are currently not routinely controlled in food. These are Cryptosporidium spp., Toxoplasma gondii and Echinococcus spp. Infection with these parasites in humans and animals, or their occurrence in food, is not notifiable in all Member States. This Opinion reviews current methods for detection, identification and tracing of these parasites in relevant foods, reviews literature on food‐borne pathways, examines information on their occurrence and persistence in foods, and investigates possible control measures along the food chain. The differences between these three parasites are substantial, but for all there is a paucity of well‐established, standardised, validated methods that can be applied across the range of relevant foods. Furthermore, the prolonged period between infection and clinical symptoms (from several days for Cryptosporidium to years for Echinococcus spp.) means that source attribution studies are very difficult. Nevertheless, our knowledge of the domestic animal lifecycle (involving dogs and livestock) for Echinoccocus granulosus means that this parasite is controllable. For Echinococcus multilocularis, for which the lifecycle involves wildlife (foxes and rodents), control would be expensive and complicated, but could be achieved in targeted areas with sufficient commitment and resources. Quantitative risk assessments have been described for Toxoplasma in meat. However, for T. gondii and Cryptosporidium as faecal contaminants, development of validated detection methods, including survival/infectivity assays and consensus molecular typing protocols, are required for the development of quantitative risk assessments and efficient control measures.

Giardia: an under-reported foodborne parasite

Foodborne zoonotic pathogens are a serious public health issue and result in significant global economic losses. Despite their importance to public health, epidemiological data on foodborne diseases including giardiasis caused by the enteric parasite, Giardia duodenalis, are lacking. This parasite is estimated to cause ∼28.2 million cases of diarrhoea each year due to contamination of food, but very few foodborne outbreaks have been documented due to the limitations of current detection as well as surveillance methods. The current method for the recovery of Giardia cysts from food matrices using immunomagnetic separation requires further standardisation and cost reduction before it can be widely used. It also should incorporate downstream molecular procedures for genotyping, and traceback and viability analyses. Foodborne giardiasis can be potentially controlled through improvements in national disease surveillance systems and the establishment of Hazard Analysis and Critical Control Point interventions across the food chain. Studies are needed to assess the true prevalence and public health impact of foodborne giardiasis.

Assessing viability and infectivity of foodborne and waterborne stages (cysts/oocysts) of Giardia duodenalis, Cryptosporidium spp., and Toxoplasma gondii: a review of methods

Giardia duodenalis, Cryptosporidium spp. and Toxoplasma gondii are protozoan parasites that have been highlighted as emerging foodborne pathogens by the Food and Agriculture Organization of the United Nations and the World Health Organization. According to the European Food Safety Authority, 4786 foodborne and waterborne outbreaks were reported in Europe in 2016, of which 0.4% were attributed to parasites including Cryptosporidium, Giardia and Trichinella. Until 2016, no standardized methods were available to detect Giardia, Cryptosporidium and Toxoplasma (oo)cysts in food. Therefore, no regulation exists regarding these biohazards. Nevertheless, considering their low infective dose, ingestion of foodstuffs contaminated by low quantities of these three parasites can lead to human infection. To evaluate the risk of protozoan parasites in food, efforts must be made towards exposure assessment to estimate the contamination along the food chain, from raw products to consumers. This requires determining: (i) the occurrence of infective protozoan (oo)cysts in foods, and (ii) the efficacy of control measures to eliminate this contamination. In order to conduct such assessments, methods for identification of viable (i.e. live) and infective parasites are required. This review describes the methods currently available to evaluate infectivity and viability of G. duodenalis cysts, Cryptosporidium spp. and T. gondii oocysts, and their potential for application in exposure assessment to determine the presence of the infective protozoa and/or to characterize the efficacy of control measures. Advantages and limits of each method are highlighted and an analytical strategy is proposed to assess exposure to these protozoa.

Parasite contamination of berries: Risk, occurrence, and approaches for mitigation

Fresh fruits and vegetables, including berries, are essential components of a healthy diet and are relevant in the prevention of chronic non-communicable diseases such as cancer and heart disease. Associations between diet and health are becoming an increasing focus of consumers, and, in response, consumption of fresh berries has been increasing rapidly in recent decades. However, increased consumption of berries may be associated with an increased risk of acquiring foodborne infections, including parasites. In this review, we describe how parasite contamination of berries may occur at several points on the farm-to-fork pathway, starting from the use of contaminated water for irrigation and pesticide application, and contact with animal and human faeces during cultivation, through contaminated harvesting equipment, and including unhygienic practices of berry pickers in the production field or others handling berries prior to consumption. Parasite transmission stages tend to be robust and therefore likely to survive from contamination in the field, through the various stages of harvesting, packaging, and sale, until consumption. We describe outbreaks of parasitic disease associated with consumption of berries - so far only described for Cyclospora and Trypanosoma cruzi, both of which are briefly introduced - but also show from survey data summarised in this review that sporadic infections or undetected outbreaks associated with contaminated berries may also occur. In addition, we describe methods for assessing whether berries are contaminated with parasite transmission stages, with emphasis on the challenges associated with analysing this particular matrix. Emphasis on current possibilities for mitigation and control are addressed; avoidance of contamination and implementation of good management practices and a hazard analysis and critical control points (HACCP) approach are essential.

Checking the detail in retail: Occurrence of Cryptosporidium and Giardia on vegetables sold across different counters in Chandigarh, India

Fresh produce has been recognized as a vehicle of infection for protozoan parasites, particularly Cryptosporidium, and, to a lesser extent, Giardia. For both parasites, outbreaks associated with fresh produce have been documented. Although documented outbreaks tend to be from industrialized countries, contamination of fresh produce with these parasites is a global issue. In developing countries, infections with these parasites are often endemic in the community, and basic infrastructure and hygiene measures may be inadequate, thus the likelihood of contamination of fresh produce with these parasites may be higher. Realization of the importance of this transmission route comes against a backdrop of raw salads and more Western culinary habits gaining a foothold, and fresh produce being encouraged as part of the diet due to their associated health benefits. However, if consumption of uncooked fresh produce is going to increase its market sector in India, it is important that it is safe. In this study, various types of fresh produce obtained from three types of vendors in Chandigarh, a major city in Northern India, were analyzed for contamination with Cryptosporidium oocysts and Giardia cysts using a method that has been previously validated in inter-laboratory spiking experiments. A total of 284 samples of different fresh produce items were analyzed, obtained from the different retailers situated in different societal layers of the city. The overall prevalence of contamination of fresh produce with these parasites was just under 11%, with 6% of the vegetables contaminated with Cryptosporidium oocysts, and 5% with Giardia cysts. Contaminated vegetables included turnip, cabbage, carrot, chili, coriander, cucumber, radishes, and tomatoes. Molecular analyses identified contamination with Cryptosporidium parvum and Giardia duodenalis of Assemblage A and Assemblage D, indicating that contamination from animals may be of relevance. Although the prevalence of contamination is similar to those reported in previous studies, the levels of contamination on some items of fresh produce were relatively high. Although the different socioeconomic areas of Chandigarh from which the samples were obtained was not associated with likelihood of contamination, fresh produce from supermarkets had heavier contamination with Cryptosporidium oocysts than fresh produce purchased through other sales outlets. The results are discussed in relation to the fresh produce chain and sales models in Chandigarh, both in terms of where contamination may occur and the potential importance of fresh produce as a transmission vehicle.