Towards standard methods for the detection of Cryptosporidium parvum on lettuce and raspberries. Part 1: development and optimization of methods

Population dynamics of Listeria spp., Salmonella spp., and Escherichia coli on fresh produce: A scoping review

Collation of the current scope of literature related to population dynamics (i.e., growth, die-off, survival) of foodborne pathogens on fresh produce can aid in informing future research directions and help stakeholders identify relevant research literature. A scoping review was conducted to gather and synthesize literature that investigates population dynamics of pathogenic and non-pathogenic Listeria spp., Salmonella spp., and Escherichia coli on whole unprocessed fresh produce (defined as produce not having undergone chopping, cutting, homogenization, irradiation, or pasteurization). Literature sources were identified using an exhaustive search of research and industry reports published prior to September 23, 2021, followed by screening for relevance based on strict, a priori eligibility criteria. A total of 277 studies that met all eligibility criteria were subjected to an in-depth qualitative review of various factors (e.g., produce commodities, study settings, inoculation methodologies) that affect population dynamics. Included studies represent investigations of population dynamics on produce before (i.e., pre-harvest; n = 143) and after (i.e., post-harvest; n = 144) harvest. Several knowledge gaps were identified, including the limited representation of (i) pre-harvest studies that investigated population dynamics of Listeria spp. on produce (n = 13, 9% of pre-harvest studies), (ii) pre-harvest studies that were carried out on non-sprouts produce types grown using hydroponic cultivation practices (n = 7, 5% of pre-harvest studies), and (iii) post-harvest studies that reported the relative humidity conditions under which experiments were carried out (n = 56, 39% of post-harvest studies). These and other knowledge gaps summarized in this scoping review represent areas of research that can be investigated in future studies.

Transmission of Cryptosporidium by Fresh Vegetables

ABSTRACT

Consumption of fresh fruits and vegetables is increasing thanks to a greater awareness of the human health benefits. Vegetables may become contaminated by enteric pathogens (protozoan parasites, bacteria, and viruses) by irrigation with contaminated water, fertilization with fresh animal manure, or by infected food handlers. Cryptosporidium spp. are fecal-oral protozoan parasites, known to be highly persistent in the environment. Efficient methods were developed for releasing and concentrating Cryptosporidium oocysts from leafy vegetables, and sensitive and specific methods were applied for detection. The aims of this review are to discuss the development and optimization of methods applied to elute, concentrate, and detect oocysts from leafy vegetables, to review the prevalence of Cryptosporidium oocysts on fresh leafy vegetables from various parts of the world, and to discuss cryptosporidiosis outbreaks resulting from the consumption of leafy vegetables. Three solutions were used with comparable efficiency to release oocysts from leafy vegetables: 1 M glycine solution; 0.1% Alconox; and filter elution buffer, with an efficiency of 36.2, 72.6, and 44%, respectively. The prevalence of Cryptosporidium oocysts was reported in developed, as well as from developing countries, although simple detection methods were applied. Most of the cryptosporidiosis outbreaks were reported in developed countries, which can be related to the efficient surveillance system. Transmission of infectious pathogens, such as Cryptosporidium, may be facilitated by fresh vegetables, which are imported and transferred from less developed to highly developed countries and consumed uncooked. Monitoring of Cryptosporidium oocysts by sensitive detection methods may enhance measures to prevent transmission by freshly consumed vegetables.

HIGHLIGHTS

Protozoan Parasites and Leafy Greens in Marrakech: Study of Occurrence Using a Molecular Method

PURPOSE

The aim of this study was to assess the presence of T. gondii, Cryptosporidium spp. oocysts, and G. duodenalis cysts, in three leafy greens (coriander, lettuce, and parsley) commonly consumed raw. Despite the recognition of the association between the parasitic illnesses and the consumption of contaminated food, there is still a lack of studies investigating the occurrence of parasitic contamination in food matrices.

METHODS

A total of 152 leafy green samples were collected in Marrakech from April 2018 to October 2019. Parasites were eluted and concentrated before detection of their DNA by real-time qPCR.

RESULTS

The analysis revealed an overall rate of contamination of 32.2% (49/152), with 29.6% (45/152) positive for T. gondii and 2.6% (4/152) for G. duodenalis, while none was positive for Cryptosporidium spp.

CONCLUSION

The results showed that humans can be exposed to protozoan parasites through vegetables consumption. Further investigations can be performed to acquire new epidemiological data to assess the public health impact of these protozoan diseases in Morocco.

Occurrence of Intestinal Parasites of Public Health Significance in Fresh Horticultural Products Sold in Maputo Markets and Supermarkets, Mozambique

(1) Background: Giardia duodenalis and Cryptosporidium are important neglected parasites associated with diarrhea, such as the emerging Enterocytozoon bieneusi. All three are foodborne parasites raising concerns in public health. This study intended to understand the intestinal parasite occurrence with emphasis on G. duodenalis, Cryptosporidium, and E. bieneusi in fresh fruits/vegetables sold in the main municipal markets of Maputo city, Mozambique. (2) Methods: A total of 321 fresh horticultural products were purchased in the rainy and dry seasons (five markets/two supermarkets/one agricultural zone). Light microscopy (LM) and PCR analysis were performed. (3) Results: By LM and/or PCR, 29.3% of the samples presented at least one parasite (rainy season: 22.9%; dry season: 35.1%). The most contaminated horticultural products: collected in dry season, from Zimpeto and Fajardo markets, lettuce and pointed white cabbage. Overall, 3.7% of G. duodenalis, 1.3% of E. bieneusi, and other intestinal parasites (pathogenic and non-pathogenic) were identified. (4) Conclusions: Important pathogenic intestinal parasites were identified in fruits/vegetables commercially purchased in Maputo City. This fact must be taken into consideration when planning the management of these horticultural markets, in order to reduce the risk of contamination of fresh produce by intestinal parasites, and to prevent foodborne diseases.

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.

Detection of Infectious Cryptosporidium parvum Oocysts from Lamb's Lettuce: CC-qPCR's Intake

Cryptosporidium spp. is responsible for several food and waterborne disease outbreaks worldwide. Healthier lifestyles attract consumers to eat, notably, fresh food like fruits and vegetables. The consumption of raw or under-cooked food increases the risk of foodborne transmission of Cryptosporidiosis. The assessment of the consumer’s exposure to Cryptosporidium danger is crucial for public health. Still, the standardized method to detect this parasite in fresh leafy greens and berry fruits has only been available since 2016 and suffers from weaknesses. Consequently, in this study, we propose a method with minimum processing steps that combines cell culture and the quantitative PCR (CC–qPCR) for detecting infectious C. parvum oocysts recovered from lamb’s lettuce. This CC–qPCR is a rapid and easy method that can detect up to one oocyst, whereas it is undetectable by classic qPCR.

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.

Removal of Giardia spp. cysts and Cryptosporididum spp. oocysts from anaerobic effluent by dissolved air flotation

Lab-scale studies were carried out to investigate the efficiency of dissolved air flotation (DAF) for the removal of Giardia spp. cysts and Cryptosporidium spp. oocysts from anaerobic effluent from the pilot UASB reactor. Raw wastewater, UASB and DAF effluent samples were collected weekly and protozoan (oo)cysts were concentrated using IMS followed by protozoa detection using immunofluorescense assay (IFA). The number of Cryptosporidium spp. oocysts in the raw wastewater was always lower than that of Giardia spp. cysts with 28-33 oocysts L^-1 and 3177-4267 cysts L^-1, respectively. Log₁₀ removal of Giardia cysts utilising polyaluminium chloride (PACl) was higher than that with FeCl₃, but no statistically significant difference between the two coagulants was observed. Cryptosporidium was absent in most of the treated effluent samples. The results indicate that DAF reached more than 2 log of cyst removal. In addition, the results demonstrated that these parasites are prevalent in the study area and E. coli and total coliforms were not good indicator microorganisms in terms of cyst and oocysts numbers.

Cryptosporidium spp., Giardia duodenalis and Toxoplasma gondii detection in fresh vegetables consumed in Marrakech, Morocco

BACKGROUND

Protozoan parasites such as Toxoplasma gondii, Giardia duodenalis, and Cryptosporidium spp., can be transmitted to humans via accidental consumption of contaminated water, fresh produce and foodstuffs. There is a lack of epidemiological data about these pathogens in Morocco. Hence the aim of this study, which is the determination of their prevalence in some leafy greens and root vegetables sold in Marrakech.

METHODS

A total of 132 vegetable samples including carrot, coriander, lettuce, parsley and radish were purchased monthly from three different markets in Marrakech from March 2017 to January 2018, pre-treated and subjected to microscopic and molecular analyses.

RESULTS

Of the 132 samples of vegetables analyzed by qPCR, the overall rate of protozoan was 21.21% (28/132); 22 samples were found to be contaminated with T. gondii, 6 with G. duodenalis, and none was positive for C. parvum/hominis. Whereas, modified Ziehl-Neelsen staining allowed the detection of Cryptosporidium spp. in 3% (4/132) of examined samples.

CONCLUSION

This survey on the presence of protozoan parasites in fresh vegetables revealed that vegetables sold in Marrakech are contaminated by these protozoan parasites, as it showed that leafy green vegetables were more susceptible for parasitic contamination than root ones.

A smartphone microscopic method for simultaneous detection of (oo)cysts of Cryptosporidium and Giardia

Background

Food and water-borne illness caused by ingestion of (oo)cysts of Cryptosporidium and Giardia is one of the major health problems globally. Several methods are available to detect Giardia cyst and Cryptosporidium oocyst in food and water. Most of the available methods require a good laboratory facility and well-trained manpower and are therefore costly. There is a need of affordable and reliable method that can be easily implemented in resource limited settings.

Methodology/Principle findings

We developed a smartphone based microscopic assay method to screen (oo)cysts of Cryptosporidium and Giardia contamination of vegetable and water samples. The method consisting of a ball lens of 1 mm diameter, white LED as illumination source and Lugols's iodine staining provided magnification and contrast capable of distinguishing (oo)cysts of Cryptosporidium and Giardia. The analytical performance of the method was tested by spike recovery experiments. The spike recovery experiments performed on cabbage, carrot, cucumber, radish, tomatoes, and water resulted in 26.8±10.3, 40.1±8.5, 44.4±7.3, 47.6±11.3, 49.2 ±10.9, and 30.2±7.9% recovery for Cryptosporidium, respectively and 10.2±4.0, 14.1±7.3, 24.2±12.1, 23.2±13.7, 17.1±13.9, and 37.6±2.4% recovery for Giardia, respectively. The spike recovery results are comparable with data obtained using commercial brightfield and fluorescence microscope methods. Finally, we tested the smartphone microscope system for detecting (oo)cysts on 7 types of vegetable (n = 196) and river water (n = 18) samples. Forty-two percent vegetable and thirty-nine percent water samples were found to be contaminated with Cryptosporidium oocyst. Similarly, thirty-one percent vegetable and thirty-three percent water samples were contaminated with Giardia cyst.

Conclusions

The newly developed smartphone microscopic method showed comparable performance to commercial microscopic methods. The new method can be a low-cost and easy to implement alternative method for simultaneous detection of (oo)cysts in vegetable and water samples in resource limited settings.

Food and water-borne illness arising from the consumption of contaminated food and water are serious health hazards globally. Cryptosporidium and Giardia are the major food and water‒borne parasites. The infection occurs mainly by (oo)cyst phase of the parasites. People in developing countries are more vulnerable to these parasites where infection is more likely underdiagnosed and underreported due to limited resources for detection. There is need of a method that is affordable and easy to implement. In this study, we developed and optimized a novel smartphone microscope method that can detect and quantify the (oo)cyst of the parasites in food and water samples. The developed method is easy to implement and affordable and provides similar performance to the other commercially available microscopic methods.

Efficiency of PEG secondary concentration and PCR for the simultaneous concentration and quantification of foodborne bacteria, viruses and protozoa

Fresh fruits are a potential source of many different pathogens, including bacteria, enteric viruses and protozoa that may pose serious health risks. The consumption of raspberries has been widely associated with large foodborne outbreaks and because of the low concentration at which most of these pathogens are found, sensitive and accurate detection methods are required. Methods that would allow for an accurate and sensitive simultaneous elution and concentration of the different classes of pathogens would decrease the time for analysis, the costs associated and the expertise necessary. In this study we explored the use of polyethylene glycol (PEG) secondary concentration to simultaneously concentrate bacteria, enteric viruses and protozoa from raspberries. PEG secondary concentration showed good recovery rates for all the organisms tested. This work indicates that PEG secondary concentration followed by quantitative (Reverse Transcription) Polymerase Chain Reaction (q(RT)PCR) may be a relevant alternative to standardized methods for the simultaneous concentration of bacteria, enteric viruses and protozoa.

Detection methods and prevalence of transmission stages of Toxoplasma gondii, Giardia duodenalis and Cryptosporidium spp. in fresh vegetables: a review

One of the ways of human parasitic infection is the accidental ingestion of vegetables contaminated with parasites, which represents a major human health hazard. This non-exhaustive review aims to evaluate studies carried out on five types of vegetables (lettuce, parsley, coriander, carrot and radish) since 2000, particularly the methods used for recovery, concentration, detection and identification of protozoan parasites such as Toxoplasma gondii, Giardia duodenalis and Cryptosporidium spp., and the results of each work. Various studies have determined the presence of pathogenic parasites in fresh vegetables with different rates; this variation in rate depends particularly on the detection method used which is related to each parasite and each vegetable type. The variation in parasitic prevalence in food could be due to different factors such as the geographical location, the size of analysed samples and the methods used for parasite detection.

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.

Microbiological Contamination of Strawberries from U-Pick Farms in Guangzhou, China

This study quantified the association of rodent fruit damage and the microbiological quality of irrigation water on the risk of microbiological contamination of strawberries collected from 18 U-pick farms across five different districts in the Guangzhou metropolitan region of southern China. Fifty-four composite strawberries samples, with or without evidence of rodent or avian foraging damage (i.e., bitten), along with 16 irrigation water samples, were collected during the spring of 2014 and winter of 2015 from our cohort of 18 farms. Composite strawberry samples and irrigation water were analyzed for total coliforms, E. coli, Salmonella, E. coli O157, Giardia, and Cryptosporidium. Total coliforms and E. coli were detected in 100% and ~90% of irrigation water samples, respectively. In contrast, Cryptosporidium was detected in only two water samples, while Salmonella, E. coli O157, and Giardia were not detected in any water samples. Strawberries with signs of being bitten by wildlife had significantly higher concentrations of total coliforms and E. coli, compared to strawberries with no physical evidence of rodent damage (p < 0.001). Similarly, Cryptosporidium was detected in 7/18 (39%) of bitten, 4/18 (22%) of edge, and 5/18 (28%) of central strawberry samples, respectively. Concentration of E. coli on strawberries (p < 0.001), air temperature (p = 0.025), and presence of Cryptosporidium in irrigation water (p < 0.001) were all associated with the risk of Cryptosporidium contamination on strawberries. Salmonella and Giardia were detected in <4% strawberry samples and E. coli O157 was not detected in any samples. These results indicate the potential food safety and public health risks of consuming unwashed strawberries from U-pick farms, and the need for improved rodent biosecurity of U-pick strawberry fields and enhanced microbiological quality of irrigation water used at these facilities.

Simultaneous detection of four protozoan parasites on leafy greens using a novel multiplex PCR assay

Pathogen contamination of fresh produce presents a health risk for consumers; however, the produce industry still lacks adequate tools for simultaneous detection of protozoan parasites. Here, a simple multiplex PCR (mPCR) assay was developed for detection of protozoan (oo)cysts and compared with previously published real-time PCR assays and microscopy methods. The assay was evaluated for simultaneous detection of Cryptosporidium, Giardia, Cyclospora cayetanensis, and Toxoplasma gondii followed by parasite differentiation via either a nested specific PCR or a restriction fragment length polymorphism (RFLP) assay. Spiking experiments using spinach as a model leafy green were performed for assay validation. Leaf-washing yielded higher recoveries and more consistent detection of parasites as compared with stomacher processing. Lowest limits of detection using the nested mPCR assay were 1-10 (oo)cysts/g spinach (in 10 g samples processed), and this method proved more sensitive than qPCR for parasite detection. Microscopy methods were more reliable for visual detection of parasites in lower spiking concentrations, but are more costly and laborious, require additional expertise, and lack molecular confirmation essential for accurate risk assessment. Overall, the nested mPCR assay provides a rapid (<24 h), inexpensive ($10 USD/sample), and simple approach for simultaneous detection of protozoan pathogens on fresh produce.

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.

An overview of methods/techniques for the detection of Cryptosporidium in food samples

Cryptosporidium is one of the most important parasitic protozoa of concern within the food production industry, worldwide. This review describes the evolution and its development, and it monitors the methodology that has been used for Cryptosporidium in food material since 1984, when the first publication appeared regarding the detection of Cryptosporidium parvum in food materials. The methods that are currently being used for the detection of Cryptosporidium oocysts in food material (mainly vegetables) and all of the other available published methods are discussed in this review. Generating more consistent and reliable data should lead to a better understanding of the occurrence, transport and fate of the oocysts in food material. Improvements in monitoring and developing effective methodology, along with food security, offer more practical possibilities for both the developed and developing worlds.

Foodborne cryptosporidiosis

Foodborne illness, the majority of which is caused by enteric infectious agents, costs global economies billions of dollars each year. The protozoan parasite Cryptosporidium is particularly suited to foodborne transmission and is responsible for >8 million cases of foodborne illness annually. Procedures have been developed for sensitive detection of Cryptosporidium oocysts on fresh produce and molecular diagnostic assays have been widely used in case linkages and infection source tracking, especially during outbreak investigations. The integrated use of advanced diagnostic techniques with conventional epidemiological studies is essential to improve our understanding of the occurrence, source and epidemiology of foodborne cryptosporidiosis. The implementation of food safety management tools such as Good Hygienic Practices (GHP), Hazard Analysis and Critical Control Points (HACCP), and Quantitative Microbial Risk Assessment (QMRA) in industrialised nations and Water, Sanitation, and Hygiene (WASH) in developing countries is central for prevention and control and foodborne cryptosporidiosis in the future.

Loop-Mediated Isothermal Amplification-Lateral-Flow Dipstick (LAMP-LFD) to detect Toxoplasma gondii oocyst in ready-to-eat salad

The apicomplexan parasite Toxoplasma gondii is the causative agent of toxoplasmosis, a foodborne zoonosis with a global distribution and estimated to cause up to 20% of the total foodborne disease burden in Europe. Association between T. gondii infection and the consumption of unwashed raw fruits and vegetables contaminated with oocysts has been reported and the increasing habit to eat pre-washed ready-to-eat salads poses a new potential risk for consumers. It is therefore important to trace the occurrence of potential contamination with this parasite to guarantee the safety of ready-to-eat vegetables. Detection of T. gondii in vegetables by molecular techniques has been achieved but low sensitivity (PCR) or expensive equipments (qPCR) limit routine applicability. Here, we describe the development and validation of a sensitive and robust method relying on a LAMP assay, targeting the 529 bp locus, to detect T. gondii oocysts down to 25 oocysts/50 g in ready-to-eat baby lettuce. The LAMP has been also adapted for a faster visualization of the result by a lateral flow dipstick chromatographic detection method.

2015 Outbreak of Cyclosporiasis Linked to the Consumption of Imported Sugar Snap Peas in Ontario, Canada

An outbreak of cyclosporiasis in Ontario, Canada, was investigated in the fall of 2015. Thirty-five confirmed and 10 probable cases were linked to the investigation. Epidemiological and food safety evidence implicated fresh sugar snap peas imported from Guatemala as the source of the outbreak. We describe here the first documented cyclosporiasis outbreak in Canada involving the consumption of sugar snap peas.

Standardization of a method for the detection of helminth eggs and larvae in lettuce

Despite reports that food-borne parasitic infections have been increasing worldwide, the methodologies employed to detect food contamination by helminths are still largely based on methodologies used to detect these pathogens in feces and water. This study sought to improve the diagnosis of parasitic contaminants in lettuce by standardizing a method for detecting helminth eggs and larvae and estimating their percentage of recovery. Sanitized lettuces were artificially contaminated with different amounts of Ascaris suum and hookworm eggs and larvae. To standardize the method, we tested liquid extractors, vegetable washing steps, and spontaneous sedimentation times. Higher percentages of egg and larvae recovery were obtained using 1 M glycine as the liquid extractor, manual shaking for 3 min and 2 h of sedimentation. Five different levels of artificial contamination (ten replicates each; n = 50) were tested using these standardized conditions, yielding an average recovery of 62.6 % (±20.2), 51.9 % (±20.0), and 50.0 % (±27.3) for A. suum eggs, hookworm eggs, and larvae, respectively. Tests were performed with a different matrix to evaluate the performance of the method. Furthermore, collaborative analytical studies performed by different laboratories produced satisfactory results. The method for the identification of helminth eggs and larvae proposed in this study proved to be simpler and more efficient than previously published procedures, thereby demonstrating its potential contribution to health surveillance and epidemiological studies.

Enhancing the Detection of Giardia duodenalis Cysts in Foods by Inertial Microfluidic Separation

The sensitivity and specificity of current Giardia cyst detection methods for foods are largely determined by the effectiveness of the elution, separation, and concentration methods used. The aim of these methods is to produce a final suspension with an adequate concentration of Giardia cysts for detection and a low concentration of interfering food debris. In the present study, a microfluidic device, which makes use of inertial separation, was designed and fabricated for the separation of Giardia cysts. A cyclical pumping platform and protocol was developed to concentrate 10-ml suspensions down to less than 1 ml. Tests involving Giardia duodenalis cysts and 1.90-μm microbeads in pure suspensions demonstrated the specificity of the microfluidic chip for cysts over smaller nonspecific particles. As the suspension cycled through the chip, a large number of beads were removed (70%) and the majority of the cysts were concentrated (82%). Subsequently, the microfluidic inertial separation chip was integrated into a method for the detection of G. duodenalis cysts from lettuce samples. The method greatly reduced the concentration of background debris in the final suspensions (10-fold reduction) in comparison to that obtained by a conventional method. The method also recovered an average of 68.4% of cysts from 25-g lettuce samples and had a limit of detection (LOD) of 38 cysts. While the recovery of cysts by inertial separation was slightly lower, and the LOD slightly higher, than with the conventional method, the sample analysis time was greatly reduced, as there were far fewer background food particles interfering with the detection of cysts by immunofluorescence microscopy.

A perspective on Cryptosporidium and Giardia, with an emphasis on bovines and recent epidemiological findings

Cryptosporidium and Giardia are two common aetiological agents of infectious enteritis in humans and animals worldwide. These parasitic protists are usually transmitted by the faecal-oral route, following the ingestion of infective stages (oocysts or cysts). An essential component of the control of these parasitic infections, from a public health perspective, is an understanding of the sources and routes of transmission in different geographical regions. Bovines are considered potential sources of infection for humans, because species and genotypes of Cryptosporidium and Giardia infecting humans have also been isolated from cattle in molecular parasitological studies. However, species and genotypes of Cryptosporidium and Giardia of bovids, and the extent of zoonotic transmission in different geographical regions in the world, are still relatively poorly understood. The purpose of this article is to (1) provide a brief background on Cryptosporidium and Giardia, (2) review some key aspects of the molecular epidemiology of cryptosporidiosis and giardiasis in animals, with an emphasis on bovines, (3) summarize research of Cryptosporidium and Giardia from cattle and water buffaloes in parts of Australasia and Sri Lanka, considering public health aspects and (4) provide a perspective on future avenues of study. Recent studies reinforce that bovines harbour Cryptosporidium and Giardia that likely pose a human health risk and highlight the need for future investigations of the biology, population genetics and transmission dynamics of Cryptosporidium and Giardia in cattle, water buffaloes and other ruminants in different geographical regions, the fate and transport of infective stages following their release into the environment, as well as for improved strategies for the control and prevention of cryptosporidiosis and giardiasis, guided by molecular epidemiological studies.

Cryptosporidium parvum Caused a Large Outbreak Linked to Frisée Salad in Finland, 2012

Over 250 individuals fell ill in five outbreaks caused by Cryptosporidium parvum in Finland, October-November 2012. The cases were connected by lunch meals at restaurants in four different cities. In two outbreaks, the same C. parvumIIdA17G1 subtype was found in patients' stool samples which supports a single source of infection. Frisée salad was the only common food item served at the restaurants, and consumption of lunch salad containing the frisée salad was associated with the illness. Lunch customers who responded that they had eaten lunch salad were three times more likely to have become ill than those who had not answered whether they had eaten the salad or not (RR 2.66; 95% Cl 1.02-6.9, P-value <0.01). Cryptosporidiosis should be considered as a causal agent in long-lasting watery diarrhoea combined with abdominal cramps, and clinical samples should be tested for Cryptosporidium at the same time bacteria and viruses are tested. Measures to prevent contamination of 'ready-to-eat vegetables' with Cryptosporidium oocysts and methods to test frozen food samples should be developed.

Detection of Cryptosporidium parvum in environmental soil and vegetables

Cryptosporidium parvum is a zoonotic protozoan parasite that causes cryptosporidial enteritis. Numerous outbreaks of cryptosporidiosis have been reported worldwide. Cryptosporidium is transmitted to hosts via consumption of contaminated water and food but also by direct contact with contaminated soil or infected hosts. The present study investigated farm soil collected from 34 locations along the western Korean peninsula and 24 vegetables purchased from local grocery markets in Seoul. The soil and vegetable samples were examined by real-time polymerase chain reaction (qPCR) to estimate the risk of infection. Eleven of 34 locations (32.4%) and 3 of 24 vegetable samples (12.5%) were contaminated with Cryptosporidium parvum, as confirmed by TaqI enzyme digestion of qPCR products and DNA sequencing. It is suggested that Cryptosporidium infection can be mediated via farm soil and vegetables. Therefore, it is necessary to reduce contamination of this organism in view of public health.

Efficacy of wash solutions in recovering Cyclospora cayetanensis, Cryptosporidium parvum, and Toxoplasma gondii from basil

Parasitic diseases can be acquired by ingestion of contaminated raw or minimally processed fresh produce (herbs and fruits). The sensitivity of methods used to detect parasites on fresh produce depends in part on the efficacy of wash solutions in removing them from suspect samples. In this study, six wash solutions (sterile E-Pure water, 3% levulinic acid-3% sodium dodecyl sulfate, 1 M glycine, 0.1 M phosphate-buffered saline, 0.1% Alconox, and 1% HCl-pepsin) were evaluated for their effectiveness in removing Cyclospora cayetanensis, Cryptosporidium parvum, and Toxoplasma gondii from basil. One hundred or 1,000 oocysts of these parasites were inoculated onto the adaxial surfaces of 25 g of basil leaves, placed in stomacher bags, and stored for 1 h at 21°C or 24 h at 4°C. Leaves were hand washed in each wash solution for 1 min. DNA was extracted from the wash solutions and amplified using PCR for the detection of all parasites. Oocysts inoculated at a concentration of 1,000 oocysts per 25 g of basil were detected in all wash solutions. At an inoculum concentration of 100 oocysts per 25 g, oocysts were detected in 18.5 to 92.6% of the wash solutions. The lowest variability in recovering oocysts from basil inoculated with 100 oocysts was observed in 1% HCl-pepsin wash solution. Oocyst recovery rates were higher at 1 h than at 24 h postinoculation. Unlike most bacteria, parasites cannot be enriched; therefore, an optimal recovery process for oocysts from suspected foods is critical. The observations in this study provide guidance concerning the selection of wash solutions giving the highest retrieval of parasite oocysts.

New developments in safety testing of soft fruits

The chapter begins by establishing the definition of soft fruit, then discusses microbial and chemical hazards that might be found in soft fruit. Methods developed for virus detection in soft fruit are reviewed and, finally, the factors that mainly affect virus detection are detailed as these pathogens are currently linked to outbreaks caused by soft fruit consumption.

Comparison of sample preparation methods for the recovery of foodborne pathogens from fresh produce

Sample preparation methods (pummeling, pulsifying, sonication, and shaking by hand) were compared for achieving maximum recovery of foodborne pathogens from iceberg lettuce, perilla leaves, cucumber, green pepper, and cherry tomato. Antimicrobial and dehydration effects also were examined to investigate causes of poor recovery of pathogens. Each produce type was inoculated with Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus at 6.0 log CFU/cm(2), and samples were prepared using the four methods. Bacterial populations recovered from the five types of produce were significantly different (P < 0.05) according to sample preparation methods and produce type. The bacterial populations recovered from pummeled and pulsified samples were higher (P < 0.05) than those recovered from sonicated and hand-shaken samples, except for cherry tomato. The number of bacteria recovered from produce was reduced (P < 0.05) from that of the inoculum by 0.16 to 2.69 log CFU/cm(2). Although extracts of iceberg lettuce, perilla leaves, cucumber, and green pepper had no antimicrobial activity, the populations of E. coli O157:H7, Salmonella Typhimurium, B. cereus, and L. monocytogenes in cherry tomato extract were slightly reduced after these treatments (P < 0.05). The pathogen populations on perilla leaves and cherry tomatoes decreased by >2 log CFU/cm(2) after exposure to 40% relative humidity for 1 h. No reduction was observed when the five pathogens were exposed to 90% relative humidity. These data suggest that pummeling and pulsifying are optimal sample preparation methods for detection of microorganisms. Acidic produce such as cherry tomato should be treated with a method that does not cause sample breakdown so that acid stress on the bacteria can be minimized. Dehydration stress also affects recovery of pathogens from produce.

Analysis of cured meat products for cryptosporidium oocysts following possible contamination during an extensive waterborne outbreak of Cryptosporidiosis

An outbreak of waterborne cryptosporidiosis in a town in northern Sweden during winter 2010 resulted in the potential exposure of cured meat products to Cryptosporidium oocysts during their manufacture. The purpose of this work was to develop a method for analyzing cured meat products for contamination with Cryptosporidium oocysts and use this method to analyze potentially contaminated product samples. A simple method of elution, concentration, separation, and detection was used, based on work with other food matrices but adapted for the relatively high fat content of cured meat surfaces. Using spiking experiments, the recovery efficiency of this method was found to be over 60%. In the analysis of the potentially contaminated products, only one putative Cryptosporidium oocyst was detected, and this was sufficiently deformed so that it could not be confirmed as an oocyst; if it was an oocyst, it was considered to have been probably deformed and inactivated prior to analysis. Based on the results of the analyses, together with data on the probable extent of contamination of the products and on our knowledge of factors, such as water activity, which affect oocyst survival, the products were safely released to the market.

Use of a common laboratory glassware detergent improves recovery of Cryptosporidium parvum and Cyclospora cayetanensis from lettuce, herbs and raspberries

The success of any protocol designed to detect parasitic protozoa on produce must begin with an efficient initial wash step. Cryptosporidium parvum and Cyclospora cayetanensis oocysts were seeded onto herbs, lettuces and raspberries, eluted with one of four wash solutions and the recovered number of oocysts determined via fluorescent microscopy. Recovery rates for fluorescein thiosemicarbazide labeled C. parvum oocysts seeded onto spinach and raspberries and washed with de-ionized water were 38.4 ± 10.1% and 34.9 ± 6.2%, respectively. Two alternative wash solutions viz. 1M glycine, pH 5.5 and a detachment solution were tested also using labeled C. parvum seeded spinach and raspberries. No statistically significant difference was noted in the recovery rates. However, a wash solution containing 0.1% Alconox, a laboratory glassware detergent, resulted in a significant improvement in oocyst recovery. 72.6 ± 6.6% C. parvum oocysts were recovered from basil when washed with 0.1% Alconox compared to 47.9 ± 5.8% using detachment solution. Also, C. cayetanensis oocysts were seeded onto lettuces, herbs and raspberries and the recovery using de-ionized water were compared to 0.1% Alconox wash: basil 17.5 ± 5.0% to 76.1 ± 14.0%, lollo rosso lettuce 38.3 ± 5.5% to 72.5 ± 8.1%, Tango leaf lettuce 45.9 ± 5.4% to 71.1 ± 7.8% and spring mix (mesclun) 39.8 ± 0.7% to 80.2 ± 11.3%, respectively. These results suggest that the use of Alconox in a wash solution significantly improves recovery resulting in the detection of these parasitic protozoa on high risk foods.

CONTROLE DE QUALIDADE ANALÍTICA DOS MÉTODOS UTILIZADOS PARA A DETECÇÃO DE PROTOZOÁRIOS PATOGÊNICOS EM AMOSTRAS DE ÁGUA

RESUMO As espécies de protozoários patogênicos de veiculação hídrica Giardia spp. e Cryptosporidium spp. foram responsáveis por cerca 90% dos surtos de gastroenterite ocorridos nos últimos 25 anos, em vários países. Critérios de avaliação das etapas referentes à detecção destes agentes em amostras de água, tais como: precisão inicial, inoculação nas amostras em água bruta e, diagnóstico e localização de erros estão abordados neste trabalho. Estes critérios devem ser correntemente aplicados e constantemente avaliados pelos laboratórios, a fim de assegurar a confiabilidade dos resultados obtidos durante um monitoramento e, assim, fornecer subsídios para uma avaliação do risco de surtos.

Infectivity of Cryptosporidium parvum oocysts after storage of experimentally contaminated apples

Irrigation water and washing water have been inferred to be associated with contamination of fresh fruits and vegetables with pathogenic microorganisms infectious for humans. The objective of the present study was to determine whether apples experimentally contaminated with Cryptosporidium oocysts represent a food safety concern. Laser scanning confocal microscopy revealed no morphological changes in Cryptosporidium parvum oocysts attached to apples after 6 weeks of cold storage, suggesting that oocysts might remain viable and possibly infectious during prolonged storage. Mice were fed apple peels from experimentally contaminated apples to determine whether oocysts had remained infectious on apples stored for 4 weeks. All mice developed cryptosporidiosis. To evaluate the strength of oocyst attachment to apples, washing methods that have been reported to be helpful for recovery of oocysts from various foodstuffs were evaluated, except that the intensity of washing was increased in the present study. None of the tested washing methods succeeded in completely removing oocysts from the apple peel. The most efficient removal (37.5%) was achieved by rigorous manual washing in water with a detergent and by agitation in an orbital shaker with Tris-sodium dodecyl sulfate buffer. Glycine and phosphate-buffered saline buffers had no effect on oocyst removal. Scanning electron microscopy revealed that some oocysts were attached in deep natural crevices in the apple exocarp and others were attached to the smooth surface of the peel. Some oocysts were closely associated with what appeared to be an amorphous substance with which they might have been attached to the apple surface.

Cryptosporidium oocysts and giardia cysts on salad products irrigated with contaminated water

A field study in Valencia, Spain, was done to determine the occurrence of Giardia and Cryptosporidium on salad products that are frequently eaten raw, such as lettuces and Chinese cabbage, and in irrigation waters. Four water samples were taken weekly 1 month before harvesting the vegetables. All water samples were analyzed using techniques included in the U.S. Environmental Protection Agency Method 1623. Standard methods for detecting protozoan parasites on salad vegetables are not available. Published techniques for the isolation of parasites from vegetables generally have low and variable recovery efficiencies. In this study, vegetables were analyzed using a recently reported method for detection of Cryptosporidium oocysts and Giardia cysts on salad products. The waters tested were positive for both Cryptosporidium and Giardia. Of 19 salad products studied, we observed Cryptosporidium in 12 samples and Giardia in 10 samples. Recoveries of the Texas Red-stained Cryptosporidium and Giardia, which were used as internal controls, were 24.5% +/- 3.5% for Cryptosporidium and 16.7% +/- 8.1% for Giardia (n = 8). This study provides data on the occurrence of Cryptosporidium and Giardia in salad products in Spain. The method was useful in the detection of Cryptosporidium oocysts and Giardia cysts on the vegetables tested, and it provides a useful analytical tool for occurrence monitoring.

Cryptosporidium: detection in water and food

Water and food are major environmental transmission routes for Cryptosporidium, but our ability to identify the spectrum of oocyst contributions in current performance-based methods is limited. Determining risks in water and foodstuffs, and the importance of zoonotic transmission, requires the use of molecular methods, which add value to performance-based morphologic methods. Multi-locus approaches increase the accuracy of identification, as many signatures detected in water originate from species/genotypes that are not infectious to humans. Method optimisation is necessary for detecting small numbers of oocysts in environmental samples consistently, and further work is required to (i) optimise IMS recovery efficiency, (ii) quality assure performance-based methods, (iii) maximise DNA extraction and purification, (iv) adopt standardised and validated loci and primers, (v) determine the species and subspecies range in samples containing mixtures, and standardising storage and transport matrices for validating genetic loci, primer sets and DNA sequences.

Highly sensitive and specific PCR assay for reliable detection of Cyclospora cayetanensis oocysts

Multiple outbreaks of food-borne gastroenteritis caused by the coccidian parasite Cyclospora cayetanensis have been reported annually in North America since 1995. Detection of C. cayetanensis contamination typically relies on laborious and subjective microscopic examination of produce washes. Molecular detection methods based on nested PCR, restriction fragment length polymorphism, or multiplex PCR have been developed for C. cayetanensis; however, they have not been adequately validated for use on food products. Further challenges include reliably extracting DNA from coccidian oocysts since their tough outer wall is resistant to lysis and overcoming PCR inhibitors in sample matrices. We describe preliminary validation of a reliable DNA extraction method for C. cayetanensis oocysts and a sensitive and specific novel PCR assay. The sensitivity and repeatability of the developed methods were evaluated by multiple DNA extractions and PCR amplifications using 1,000-, 100-, 10-, or 1-ooycst aliquots of C. cayetanensis oocysts in water or basil wash sediment. Successful PCR amplification was achieved on 15 and 5 replicates extracted from aliquots containing 1,000 oocysts in water and basil wash, respectively. All 45 replicates of the 100-oocyst aliquots in water and 5 in basil wash were amplified successfully, as were 43/45 and 41/45 of the 10- and 1-oocyst aliquots in water and 9/15 and 2/15 in basil wash, respectively. The developed primers showed no cross-reactivity when tested against bacteria, nematodes, and protozoans, including Eimeria, Giardia, and Cryptosporidium. Our results indicate that these methods are specific, can reliably detect a single oocyst, and overcome many of the limitations of microscopic diagnosis.

Development of a method for detection of Giardia duodenalis cysts on lettuce and for simultaneous analysis of salad products for the presence of Giardia cysts and Cryptosporidium oocysts

We report a method for detecting Giardia duodenalis cysts on lettuce, which we subsequently use to examine salad products for the presence of Giardia cysts and Cryptosporidium oocysts. The method is based on four basic steps: extraction of cysts from the foodstuffs, concentration of the extract and separation of the cysts from food materials, staining of the cysts to allow their visualization, and identification of cysts by microscopy. The concentration and separation steps are performed by centrifugation, followed by immunomagnetic separation using proprietary kits. Cyst staining is also performed using proprietary reagents. The method recovered 46.0% +/- 19.0% (n = 30) of artificially contaminating cysts in 30 g of lettuce. We tested the method on a variety of commercially available natural foods, which we also seeded with a commercially available internal control, immediately prior to concentration of the extract. Recoveries of the Texas Red-stained Giardia cyst and Cryptosporidium oocyst internal controls were 36.5% +/- 14.3% and 36.2% +/- 19.7% (n = 20), respectively. One natural food sample of organic watercress, spinach, and rocket salad contained one Giardia cyst 50 g(-1) of sample as an indigenous surface contaminant.

A collaborative study on a Nordic standard protocol for detection and enumeration of thermotolerant Campylobacter in food (NMKL 119, 3. Ed., 2007)

A Nordic standard protocol for detection and enumeration of thermotolerant Campylobacter in food has been elaborated (NMKL 119, 3. Ed., 2007). Performance and precision characteristics of this protocol were evaluated in a collaborative study with participation of 14 laboratories from seven European countries. The laboratories performed qualitative, semi-quantitative and quantitative analyses on samples of chicken meat, cut lettuce, and milk artificially inoculated with different concentrations including blank duplicates of one strain of Campylobacter coli (SLV-271) and one strain of Campylobacter jejuni (SLV-542). Expected concentrations (95% C.I.) (cfu g(-1) or ml(-1)) of both strains in matrices were 0.6-1.4 and 23-60 for qualitative detection, and 0.6-1.4; 23-60; and 420-1200 for semi-quantitative detection. For quantitative determination, the expected concentrations of C. jejuni/C. coli were 420-1200/580-1100; 2100-6000/6300-11,000; and 4100-11,000/53,000-97,000 cfu g(-1) or ml(-1). The qualitative and semi-quantitative techniques resulted in comparable detection. The overall specificity and sensitivity of the detection techniques was 98.6% (95% C.I.: 95.1-99.8%) and 82.8% (C.I.: 78.4-86.6%), respectively. The sensitivity was not influenced by food matrix (P=0.359), but was significantly lower for C. coli compared to C. jejuni (P=0.007) and for concentrations below 1.4 cfu g(-1) (P<0.001). The detection techniques were therefore only considered satisfactory for detection of Campylobacter concentrations above approximately 25 cfu g(-1) for all matrices tested, which was supported by calculation of values for accordance, concordance, and concordance odds ratio. No statistical difference was found between enumerations obtained by the semi-quantitative and quantitative techniques for comparable concentrations of Campylobacter (420-1200 cfu g(-1) or cfu ml(-1)) (P=0.104). Both techniques underestimated concentrations of thermotolerant Campylobacter in milk. The semi-quantitative technique estimated low inoculation levels of Campylobacter more correctly than the high inoculation levels. Counts obtained on the two selective plating media, Abeyta-Hunt-Bark agar added to it 0.1% triphenyl tetrazolium chloride and modified charcoal cephoperazone desoxycholate agar were not significantly different (P=0.143). Expressed as an absolute difference between log(10)-transformed results, the overall values for repeatability (r) and reproducibility (R) were r=log(10) 0.43 and R=log(10) 1.99, respectively. By omitting results from laboratories with high level of variability in results, R was reduced to log(10) 1.88. We suggest that the poor detection of low numbers, the underestimation in milk samples, and the large variation between laboratories can be explained by the general difficulties in handling Campylobacter. In conclusion, NMKL 119, 3. Ed., 2007, is regarded as an acceptable protocol for detection of thermotolerant Campylobacter at concentrations above 25 cfu g(-1) and also for enumeration of thermotolerant Campylobacter in chicken meat.

Cryptosporidium and Giardia as foodborne zoonoses

Cryptosporidium and Giardia are major causes of diarrhoeal disease in humans, worldwide and are major causes of protozoan waterborne diseases. Both Cryptosporidium and Giardia have life cycles which are suited to waterborne and foodborne transmission. There are 16 'valid'Cryptosporidium species and a further 33+ genotypes described. Parasites which infect humans belong to the Giardia duodenalis "type", and at least seven G. duodenalis assemblages are recognised. Cryptosporidium parvum is the major zoonotic Cryptosporidium species, while G. duodenalis assemblages A and B have been found in humans and most mammalian orders. In depth studies to determine the role of non-human hosts in the transmission of Cryptosporidium and Giardia to humans are required. The use of harmonised methodology and standardised and validated molecular markers, together with sampling strategies that provide sufficient information about all contributors to the environmental (oo)cyst pool that cause contamination of food and water, are recommended. Standardised methods for detecting (oo)cysts in water are available, as are optimised, validated methods for detecting Cryptosporidium in soft fruit and salad vegetables. These provide valuable data on (oo)cyst occurrence, and can be used for species and subspecies typing using appropriate molecular tools. Given the zoonotic potential of these organisms, epidemiological, source and disease tracking investigations involve multidisciplinary teams. Here, the role of the veterinarian is paramount, particularly in understanding the requirement for adopting comprehensive sampling strategies for analysing both sporadic and outbreak samples from all potential non-human contributors. Comprehensive sampling strategies increase our understanding of parasite population biology and structure and this knowledge can be used to determine what level of discrimination is required between isolates. Genetic exchange is frequent in C. parvum populations, leading to recombination between alleles at different loci, the generation of a very large number of different genotypes and a high level of resolution between isolates. In contrast, genetic exchange appears rare in Cryptosporidium hominis and populations are essentially clonal with far fewer combinations of alleles at different loci, resulting in a much lower resolution between isolates with many being of the same genotype. Clearly, more markers provide more resolution and high throughput sequencing of a variety of genes, as in multilocus sequence typing, is a way forward. Sub-genotyping tools offer increased discrimination, specificity and sensitivity, which can be exploited for investigating the epidemiology of disease, the role of asymptomatic carriers and contaminated fomites and for source and disease tracking for food and water contaminated with small numbers of (oo)cysts.