Detection of protozoan parasites and microsporidia in irrigation waters used for crop production

Filters comprised of sand and Zero Valent Iron hold promise as tools to mitigate risk posed by Cyclospora cayetanensis oocysts

Irrigation water contaminated by human fecal material may elevate the risk of produce contamination with the enteric parasite Cyclospora cayetanensis. Oocysts of C. cayetanensis are resistant to commonly used disinfectants and a method of removing C. cayetanensis from irrigation water would mitigate this risk. We evaluated zero valent iron (ZVI) sand filtration as one such method. We sought to determine if sand filters containing ZVI outperformed those without ZVI. We first evaluated the abundant poultry parasites Eimeria maxima, E. tenella and E. acervulina as surrogates for C. cayetanensis. We determined if a miniaturized gravity fed ZVI-sand filter, scaled to evaluate scarce supplies of C. cayetanensis oocysts, provided useful information about the performance of larger filtration systems. Filters were inoculated with oocysts, rinsed, and the resulting filtrate examined microscopically for oocysts. We performed experiments to measure the effect of varying ZVI concentrations, repeated filter use, simulated agricultural water, and oocyst size and condition. We then compared the performance of mini filters to that of larger, gravity-fed pool filters and found that ZVI-sand filtration was far more effective at removing Eimeria spp. from water when compared to sand filtration, at both scales. Sand mini filters retained 13-54 % of E. acervulina oocysts, and pool filters retained 82 %, but when combined with 50 % (mini filter) or 35 % (pool filter) v/v ZVI, mini filters retained 89-99 % of oocysts and pool filters retained >99 %. The effectiveness of the mini filters increased with increasing ZVI concentration, and the addition of ZVI far outweighed the influence of any other measured variable. We then performed experiments including C. cayetanensis, which provided similar results to those utilizing Eimeria; 59 % of inoculated C. cayetanensis oocysts were retained in sand mini filters, and 97 % in mini filters composed of 35 % v/v ZVI. In sum, ZVI is highly effective in removing oocysts from water and Eimeria is a useful surrogate for C. cayetanensis to assess filtration. ZVI-sand filtration shows promise as a tool to mitigate the risk of C. cayetanensis contamination of irrigation water. Further studies should evaluate the performance of ZVI-sand in pressurized fast filtration systems under a range of field conditions.

Unveiling risks in healthy food: Vegetables and fruits are linked to the distribution chain of protozoan parasites

Vegetable and fruit contamination is recognized as a significant parasite transmission route. This review presents the current state of vegetables ad fruits contamination with food-borne parasitic protozoa worldwide. We consider the methodologies and strategies for detecting parasitic stages developed in the last decade and the contamination data. Asia had the highest number of reports (94 studies), followed by Africa (74 studies). At the country level, with 41 studies, Iran had the most reports among other countries, followed by Nigeria (28 studies). According to the studies included in the current review, 41.22% of vegetables and fruits were contaminated with different species of protozoan parasites. Among different continents, Asia accounted for the highest contamination rate of protozoan parasites (57.12%). Giardia spp. (10%) had the highest contamination rate in vegetables and fruits, followed by Entamoeba coli (8%), E. histolytica/dispar (7%), and Cryptosporidium spp. (6%). This study provides essential data for health authorities to develop food safety programs. The presence of protozoan parasites in fruits and vegetables highlights the critical need for maintaining rigorous food safety measures across the entire production and distribution process, particularly in countries that are major producers and distributors of these food items.

Microsporidia in Commercially Harvested Marine Fish: A Potential Health Risk for Consumers

Microsporidia are widely spread obligate intracellular fungal pathogens from vertebrate and invertebrate organisms, mainly transmitted by contaminated food and water. This study aims to detect the presence of major human-pathogenic microsporidia, i.e., Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon hellem, and Encephalitozoon cuniculi, in the gastrointestinal tract of commercially harvested marine fish from Mediterranean coast of the Comunidad Valenciana, Eastern Spain. A total of 251 fish, 138 farmed fish and 113 wild fish from commercial fishing were tested by SYBR Green real-time PCR, enabling the simultaneous detection of the four targeted species. E. intestinalis/hellem was found in 1.45% of farmed fish and 7.96% of wild fish, while Enterocytozoonidae was detected in 2.90% and 18.58% of farmed and wild fish, respectively. E. cuniculi was not detected in any of the analyzed specimens. To the authors' knowledge, this is the first report of E. intestinalis/hellem in fish, particularly in marine fish. Although the role of fish in these species' epidemiology remains unknown, this finding points out a potential public health risk linked to fish consumption. Further studies are necessary to characterize these microsporidia in fish hosts better and to elucidate their epidemiological role.

Global prevalence and genotype distribution of Microsporidia spp. in various consumables: a systematic review and meta-analysis

Water and food sources play a major role in the distribution and transfer of microsporidia infection to animals and humans. So, this systematic review and meta-analysis aimed to assess the status and genetic diversity of microsporidia infection in water, vegetables, fruits, milk, cheese, and meat. The standard protocol of Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines was followed. Scopus, PubMed, Web of Science, and Google Scholar were searched from 1 January 2000 and 1 February 2023. The point estimates and 95% confidence intervals (CIs) were calculated using a random-effects model. Of the 1,308 retrieved studies, 35 articles were included in the final meta-analysis. The pooled prevalence of microsporidia infection in mixed water, mixed fruits, mixed vegetables, and milk was 43.3% (95% CI, 33-54.2%; I², 94.86%), 35.8% (95% CI, 5.3-84.8%; I², 0), 12% (95% CI, 4.9-26.6%; I², 96.43%), and 5.8% (95% CI, 2.7-12%; I², 83.72%), respectively. Considering the genotypes, microsporidia with genotype D in water sources and genotype CD6 in vegetables/fruits were the highest reported genotypes. Given the relatively high prevalence of microsporidiosis (especially in water sources), designing strategies for control, and prevention of microsporidia infection in these sources should be recommended.

Detection of Giardia duodenalis and Toxoplasma gondii in soil and water samples in the Quindío River basin, Colombia

Two zoonotic protozoan pathogens, Giardia duodenalis and Toxoplasma gondii, are important causes of waterborne infections in the Quindío region in Colombia. No previous data exist on how contamination occurs at the source for drinking water consumed by the human population in this region. Our aim was to describe the frequency of G. duodenalis and T. gondii DNA in 11 sampling points during a five-month period in water and adjacent soil at the Quindío River basin (Andean region in the central western part of Colombia). The study employed nested PCR for T. gondii, using the B1 gene as the amplification target, and single-round PCR for G. duodenalis assemblage A and assemblage B, amplifying the gdh gene, followed by DNA sequencing. In 50 soil samples, 28% (14/50) were positive for T. gondii. For G. duodenalis, distribution was in equal parts for assemblage A (8%; 4/50) and assemblage B (8%, 4/50). Genotyping of T. gondii sequences showed two soil samples with type I strain, another two samples of soil with type III strain, but most samples were of unidentified strains. In water samples, T. gondii was detected in 9.1% (5/55), G. duodenalis assemblage A in 34.5% (19/55), and G. duodenalis assemblage B in 12.7% (7/55). T. gondii DNA positivity was associated with lower soil temperature (p = 0.0239). Presence of G. duodenalis and T. gondii was evidenced in soil and water samples in the Quindío River basin, indicating soil as the potential source of contamination for the river that it is destined for human consumption. Monitoring these protozoa in drinking water is necessary to prevent public health risks in human populations.

A multidisciplinary review about Encephalitozoon cuniculi in a One Health perspective

Encephalitozoon cuniculi is a microsporidian parasite mostly associated with its natural host, the rabbit (Oryctolagus cuniculus). However, other animals can be infected, like other mammals, birds, and even humans. Although it usually causes subclinical infection, it can also lead to encephalitozoonosis, a clinical disease characterized by neurological, ocular, and/or renal signs that can be even fatal, especially in immunocompromised individuals. Therefore, this multidisciplinary review contributes with updated information about the E. cuniculi, deepening in its molecular and genetic characterization, its mechanisms of infection and transmission, and its prevalence among different species and geographic locations, in a One Health perspective. Recent information about the diagnostic and therapeutic approach in the main host species and the prophylaxis and infection control measures currently suggested are also discussed.

Microbial Safety of Beef Along Beef Value Chains in the Ashaiman Municipality of Ghana

Food from animal sources continues to be a significant food safety hazard. This study determined the microbial quality and safety of beef along beef value chains with case studies in the Ashaiman Municipality of Ghana. Raw beef samples were collected from four slaughter slabs in the Ashaiman Municipality and analyzed using standard microbiological methods to determine the quality and prevalence of specific pathogens, including Salmonella species, Listeria monocytogenes (L. monocytogenes), and Brucella species, as well as Toxoplasma gondii (T. gondii), Cyclospora cayetanensis (C. cayetanensis), and Cryptosporidium parvum (C. parvum). Data regarding food safety knowledge and practices were collected and observed from stakeholders (cattle farmers, butchers, and beef retailers). Salmonella typhimurium was isolated from 7.5% (6/80) of the total raw beef samples. However, L. monocytogenes, Brucella spp., T. gondii, C. cayetanensis, and C. parvum were not isolated in this study. The mean level of microbial contamination of beef from the slaughter slabs/abattoir [5.2 Log10 colony-forming unit (CFU)/g] was not significantly different (p > 0.05) from the mean level observed at retail points (5.4 Log10 CFU/g). However, the mean coliform count of 4.3 Log10 CFU/g recorded at retail shops exceeded the permissible limits of 104 CFU/g (4 Log10 CFU/g) required by the Ghana Standards Authority for safety of meat and carcasses. Knowledge on food safety was at average level for butchers and retailers. Unhygienic practices and poor sanitary conditions at the abattoirs and retail shops observed could be the main contributing factors to microbial contamination of raw beef. Continuous education for meat handlers on issues of food safety and monitoring of slaughter activities will reduce the rate and level of contamination of beef.

Chronic Infections in Mammals Due to Microsporidia

Microsporidia are pathogenic organism related to fungi. They cause infections in a wide variety of mammals as well as in avian, amphibian, and reptilian hosts. Many microsporidia species play an important role in the development of serious diseases that have significant implications in human and veterinary medicine. While microsporidia were originally considered to be opportunistic pathogens in humans, it is now understood that infections also occur in immune competent humans. Encephalitozoon cuniculi, Encephalitozoon intestinalis, and Enterocytozoon bieneusi are primarily mammalian pathogens. However, many other species of microsporidia that have some other primary host that is not a mammal have been reported to cause sporadic mammalian infections. Experimental models and observations in natural infections have demonstrated that microsporidia can cause a latent infection in mammalian hosts. This chapter reviews the published studies on mammalian microsporidiosis and the data on chronic infections due to these enigmatic pathogens.

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

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

Ecological and public health significance of Enterocytozoon bieneusi

Enterocytozoon bieneusi, a fungus-like protist parasite, causes symptomatic and asymptomatic intestinal infections in terrestrial animals and is also abundant in the environment. This parasite has been isolated from a variety of host types including humans, livestock, companion animals, birds, and wildlife, as well as the natural and urban environments including drinking source water, coastal water, recreational water, wastewater, vegetables in retail markets, and raw milk on farms. E. bieneusi exhibits high genetic diversity among host species and environmental sources and at least 500 genotypes have been identified thus far. Since its discovery in AIDS patients in 1985, scientists across the world have worked to demonstrate the natural history and public health potential of this pathogen. Here we review molecular typing studies on E. bieneusi and summarize relevant data to identify the potential sources of human and nonhuman infections and environmental contamination. This review also discusses the possible transmission routes of E. bieneusi and the associated risk factors, and advocates the importance of the One Health approach to tackle E. bieneusi infections.

Prevalence, Distribution, and Diversity of Salmonella Strains Isolated From a Subtropical Lake

This study investigated the prevalence, serovar distribution, antimicrobial resistance, and pulsed field gel electrophoresis (PFGE) typing of Salmonella enterica isolated from Lake Zapotlán, Jalisco, Mexico. Additionally, the association of the presence of Salmonella with physicochemical and environmental parameters was analyzed using Pearson correlation analysis and principal component analysis (PCA). Salmonella spp. were identified in 19 of 63 (30.15%) samples. The prevalence of Salmonella was positively correlated with air temperature, electrical conductivity, pH, and dissolved oxygen and negatively correlated with relative humidity, water temperature, turbidity, and precipitation. The predominant serotype identified was Agona (68.48%), followed by Weltevreden (5.26%), Typhimurium (5.26%), and serogroup B (21.05%). Overall, the highest detected antimicrobial resistance was toward colistin (73.68%), followed by sulfamethoxazole (63.15%), tetracycline (57.89%), nalidixic acid (52.63%), and trimethoprim (52.63%). All Salmonella strains were genetically diverse, with a total of 11 XbaI and four BlnI profiles on PFGE. The use of these two enzymes allowed differentiate strains of Salmonella of the same serotype. The results obtained in this study contribute to a better understanding of the Salmonella spp. ecology in an endorheic subtropical lake and provide information for decision makers to propose and implement effective strategies to control point and non-point sources of pathogen contamination.

Survival and infectivity of Toxoplasma gondii and Cryptosporidium parvum oocysts bioaccumulated by Dreissena polymorpha

AIMS

The study was aimed to understand the depuration process of Cryptosporidium parvum and Toxoplasma gondii oocysts by zebra mussel (Dreissena polymorpha), to consider the use of the zebra mussel as a bioremediation tool.

MATERIALS AND METHODS

Two experiments were performed: (i) individual exposure of mussel to investigate oocyst transfers between bivalves and water and (ii) in vivo exposure to assess the ability of the zebra mussel to degrade oocysts.

RESULTS

(i) Our results highlighted a transfer of oocysts from the mussels to the water after 3 and 7 days of depuration; however, some oocysts were still bioaccumulated in mussel tissue. (ii) Between 7 days of exposure at 1000 or 10 000 oocysts/mussel/day and 7 days of depuration, the number of bioaccumulated oocysts did not vary but the number of infectious oocysts decreased.

CONCLUSION

Results show that D. polymorpha can release oocysts in water via (pseudo)faeces in depuration period. Oocysts remain bioaccumulated and infectious oocyst number decreases during the depuration period in zebra mussel tissues. Results suggest a degradation of bioaccumulated C. parvum and T. gondii oocysts.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlighted the potential use of D. polymorpha as a bioremediation tool to mitigate of protozoan contamination in water resources.

Fate and Biofilm Formation of Wild-Type and Pressure-Stressed Pathogens of Public Health Concern in Surface Water and on Abiotic Surfaces

Since the historic outbreak near Broad Street in London, which serves as cornerstone of modern epidemiology, infectious diseases spread in surface and sub-surface water has been a persisting public health challenge. The current study investigated persistence of wild-type and pressure-stressed Listeria monocytogenes, Escherichia coli O157:H7, and non-typhoidal Salmonella enterica serovars in surface water stored aerobically for up to 28 days at 5, 25, and 37 °C. Additionally, biofilm formation of wild-type and pressure-stressed non-typhoidal Salmonella serovars were monitored on surface of stainless steel and rubber coupons for 28 days at 25 and 37 °C. While L. monocytogenes exhibited a lower (p < 0.05) survival rate at 5 °C, relative to the two Gram-negative pathogens, at higher temperatures of 25 and 37 °C, all three pathogens exhibited similar (p ≥ 0.05) trends for survival in surface water. Both wild-type and pressure-stressed Salmonella serovars in the vast majority of tested times, temperatures, and surfaces exhibited comparable (p ≥ 0.05) persistence and biofilm formation capability. Our study thus indicates the occurrence of contamination could lead to prolonged survival of these microorganisms in low-nutrient environments and highlights the need for preventive measures such as those articulated under Produce Safety Rule of the U.S. Food Safety Modernization Act.

Encephalitozoon cuniculi infection in farmed rabbits in Egypt

BACKGROUND

Encephalitozoon cuniculi is an important microsporidian parasite with zoonotic potential. The present study highlights the impact of encephalitozoonosis on rabbit health in Egypt. Three rabbit farms in Giza, with a total of 16,400 rabbits were investigated due to occurrence of rabbits displaying clinical signs consistent with encephalitozoonosis.

RESULTS

Clinical signs observed during a 4 months observation period in 2018 included vestibular disease, paresis, limb paralysis, cataracts, phacoclastic uveitis, frequent urination, marked decrease in body weight and in some pregnant females, also repeated abortions. The total morbidity rates in adult and young rabbits were 76.7% and 81.5%, respectively. The highest mortality rate was recorded in offspring (12.3%), followed by dams (5.6%), and the lowest recorded mortality rate was in males (0.04%). Post-mortem findings included enteritis, pale enlarged kidneys, congested leptomeninges, focal brain necrosis, and endometrial congestion. Histopathological examination revealed nonsuppurative meningoencephalitis and glial nodules with central necrosis in the brain, vacuolation and necrosis of renal tubular epithelium, and corneal ulceration and ruptured lens capsule with fragmentation of lenticular fibres. E. cuniculi were observed in the brain, retinal ganglion cells, kidneys, and liver. Transmission electron microscopy examination revealed the presence of different developmental stages of E. cuniculi in the brain and kidney. Presence of E. cuniculi was confirmed by conventional polymerase chain reaction using a universal 16S gene for Encephalitozoon spp. followed by sequencing and sequence analysis.

CONCLUSIONS

The presence of E. cuniculi in rabbits was confirmed at three farms in Egypt. Nervous signs and ocular lesions were the most predominant findings in these farms.

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.

Review of water quality criteria for water reuse and risk-based implications for irrigated produce under the FDA Food Safety Modernization Act, produce safety rule

Questions related to the safety of alternative water sources, such as recycled water or reclaimed water (including grey water, produced water, return flows, and recycled wastewater), for produce production have been largely un-explored at the detail warranted for protection of public health. Additionally, recent outbreaks of Escherichia coli (E. coli) in fresh produce, in which agricultural water was suspected as the source, coupled with heightened media coverage, have elevated fruit and vegetable safety into the forefront of public attention. Exacerbating these concerns, new Federal regulations released by the U.S. Food and Drug Administration (FDA) as part of implementation of the FDA Food Safety Modernization Act (FSMA), require testing of agricultural water quality for generic E. coli. Here, we present a review of water quality criteria - including surface water, groundwater recreational water, and water reuse - in an attempt to better understand implications of new FDA regulations on irrigated produce. In addition, a Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate risks from pathogen contamination of food crops eaten fresh under the context of FDA regulations to provide perspective on current water reuse regulations across the country. Results indicate that irrigation water containing 126 CFU/100 mL of E. coli correspond to a risk of GI illness (diarrhea) of 9 cases in 100,000,000 persons (a 0.000009% risk) for subsurface irrigation, 1.1 cases in 100,000 persons (a 0.0011% risk) for furrow irrigation, and 1.1 cases in 1000 persons (a 0.11% risk) for sprinkler irrigation of lettuce. In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations. These findings, while limited to a one-time exposure event of lettuce irrigated with water meeting FSMA water quality regulations, highlight the need for additional assessments to determine if the scientific-basis of the regulation is protective of public health.

Motility and Survival of Salmonella Enterica Subspecies Enterica Serovar Enteritidis in Tomato Plants (Solanum lycopersicum L)

The presence of enteropathogens such as Salmonella affects the quality and safety of vegetables that are consumed in a minimally processed state. Worldwide, tomatoes are one of the main vegetables whose raw consumption has caused health alerts. As such, the aim of this study was to determine the motility and survival of Salmonella enterica subspecies enterica serovar Enteritidis on greenhouse-grown tomato plants. A completely randomized experimental design was used, and bacteria were inoculated into the substrate at the time of transplanting as well as by puncturing the plant stem, petiole, and peduncle during the vegetative, flowering, and fruiting stages. Survival was monitored throughout the production cycle; motility was evaluated separately in plant organs separated from the point of inoculation. Salmonella enteritidis survived the 120 days of the experiment both at the point of inoculation and in other organs of the tomato plant. For all treatments, there was a significant difference (P < 0.05) between bacterial counts in the root (12.45 ± 2.52 to 160 ± 4.01 CFU/g), stem (16.10 ± 2.31 to 90.55 ± 3.62 CFU/g), flower (7.0 ± 2.15 to 51.10 ± 3.80 CFU/g), and fruit (8.75 ± 2.38 to 28.2 ± 3.29 CFU/g). The results of the study indicate that Salmonella enteritidis in contact with tomato plants is a latent danger because its ability to enter, survive, and move within tomato plants until reaching the fruit, limits the effectiveness of commonly used disinfection methods, it would potentiate the risk to human health.

Local Food Systems Food Safety Concerns

Foodborne disease causes an estimated 48 million illnesses and 3,000 deaths annually (Scallan E, et al., Emerg Infect Dis 17:7-15, 2011), with U.S. economic costs estimated at $152 billion to $1.4 trillion annually (Roberts T, Am J Agric Econ 89:1183-1188, 2007; Scharff RL, http://www.pewtrusts.org/en/research-and-analysis/reports/0001/01/01/healthrelated-costs-from-foodborne-illness-in-the-united-states, 2010). An increasing number of these illnesses are associated with fresh fruits and vegetables. An analysis of outbreaks from 1990 to 2003 found that 12% of outbreaks and 20% of outbreak-related illnesses were associated with produce (Klein S, Smith DeWaal CS, Center for Science in the Public Interest, https://cspinet.org/sites/default/files/attachment/ddreport.pdf, June 2008; Lynch M, Tauxe R, Hedberg C, Epidemiol Infect 137:307-315, 2009). These food safety problems have resulted in various stakeholders recommending the shift to a more preventative and risk-based food safety system. A modern risk-based food safety system takes a farm-to-fork preventative approach to food safety and relies on the proactive collection and analysis of data to better understand potential hazards and risk factors, to design and evaluate interventions, and to prioritize prevention efforts. Such a system focuses limited resources at the points in the food system with the likelihood of having greatest benefit to public health. As shared kitchens, food hubs, and local food systems such as community supported agriculture are becoming more prevalent throughout the United States, so are foodborne illness outbreaks at these locations. At these locations, many with limited resources, food safety methods of prevention are rarely the main focus. This lack of focus on food safety knowledge is why a growing number of foodborne illness outbreaks are occurring at these locations.

Epidemiological Evidence and Health Risks Associated With Agricultural Reuse of Partially Treated and Untreated Wastewater: A Review

The use of partially treated and untreated wastewater for irrigation is beneficial in agriculture but may be associated with human health risks. Reports from different locations globally have linked microbial outbreaks with agricultural reuse of wastewater. This article reviews the epidemiological evidence and health risks associated with this practice, aiming toward evidence-based conclusions. Exposure pathways that were addressed in this review included those relevant to agricultural workers and their families, consumers of crops, and residents close to areas irrigated with wastewater (partially treated or untreated). A meta-analysis gave an overall odds ratio of 1.65 (95% CI: 1.31, 2.06) for diarrheal disease and 5.49 (95% CI: 2.49, 12.10) for helminth infections for exposed agricultural workers and family members. The risks were higher among children and immunocompromised individuals than in immunocompetent adults. Predominantly skin and intestinal infections were prevalent among individuals infected mainly via occupational exposure and ingestion. Food-borne outbreaks as a result of crops (fruits and vegetables) irrigated with partially or untreated wastewater have been widely reported. Contamination of crops with enteric viruses, fecal coliforms, and bacterial pathogens, parasites including soil-transmitted helminthes (STHs), as well as occurrence of antibiotic residues and antibiotic resistance genes (ARGs) have also been evidenced. The antibiotic residues and ARGs may get internalized in crops along with pathogens and may select for antibiotic resistance, exert ecotoxicity, and lead to bioaccumulation in aquatic organisms with high risk quotient (RQ). Appropriate mitigation lies in adhering to existing guidelines such as the World Health Organization wastewater reuse guidelines and to Sanitation Safety Plans (SSPs). Additionally, improvement in hygiene practices will also provide measures against adverse health impacts.

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.

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.

Human infective potential of Cryptosporidium spp., Giardia duodenalis and Enterocytozoon bieneusi in urban wastewater treatment plant effluents

Cryptosporidiosis, giardiasis, and microsporidiosis are important waterborne diseases. In the standard for wastewater treatment plant (WWTP) effluents in China and other countries, the fecal coliform count is the only microbial indicator, raising concerns about the potential for pathogen transmission through WWTP effluent reuse. In this study, we collected 50 effluent samples (30 L/sample) from three municipal WWTPs in Shanghai, China, and analyzed for Cryptosporidium spp., Giardia duodenalis and Enterocytozoon bieneusi by microscopy and/or polymerase chain reaction (PCR). Moreover, propidium monoazide (PMA)-PCR was used to assess the viability of oocysts/cysts. The microscopy and PCR-positive rates for Cryptosporidium spp. were 62% and 40%, respectively. The occurrence rates of G. duodenalis were 96% by microscopy and 92-100% by PCR analysis of three genetic loci. Furthermore, E. bieneusi was detected in 70% (35/50) of samples by PCR. Altogether, 10 Cryptosporidium species or genotypes, two G. duodenalis genotypes, and 11 E. bieneusi genotypes were found, most of which were human-pathogenic. The chlorine dioxide disinfection employed in WWTP1 and WWTP3 failed to inactivate the residual pathogens; 93% of the samples from WWTP1 and 83% from WWTP3 did not meet the national standard on fecal coliform levels. Thus, urban WWTP effluents often contain residual waterborne human pathogens.

Prevalence of Some Human Enteroparasites in Commonly Consumed Raw Vegetables in Tabuk, Saudi Arabia

The problem of parasitic contamination of food, especially fresh vegetables, is not limited to personal hygiene during food preparation but is also widely dependent on the source of the food and the handling it undergoes before it gets to the consumer. The objective of the present study was to evaluate parasitic contamination in eight common raw vegetables in Tabuk, Kingdom of Saudi Arabia. A total of 400 samples of raw vegetables obtained from wholesale and retail markets were examined for helminth eggs and larvae and for cysts of different parasites, using standard methods. The prevalence of the parasites was 20.65% in cucumber, 15.76% in cabbage, 14.67% in pea, 14.13% in cress, 13.04% in lettuce, 10.33% in carrot, 8.70% in green onion, and 2.72% in tomato. Statistical analysis showed a significant difference (P < 0.05) for Entamoeba spp. cysts, Ascaris lumbricoides eggs, Entamoeba coli cysts, and unknown isolated parasite cysts. Parasites are common in vegetables that are frequently eaten raw and, for this reason, may pose a health risk for consumers in Tabuk.

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.

Irrigation water quality and the benefits of implementing good agricultural practices during tomato (Lycopersicum esculentum) production

The implementation of good agricultural practices (GAP) from irrigation water to the tomato packaging process enhances the safety of fresh produce and its value throughout the food chain. The aim of the present study was to show that fresh produce farms that apply and enforce GAP could reduce the presence of Salmonella in finished produce. Samples were collected biweekly from six packing houses from the central region of Sinaloa, México, for the isolation of Salmonella spp by the ISO 6579:2002 method, and the isolated strains were serotyped and genotyped by the Kauffmman-White scheme and pulsed field gel electrophoresis (PFGE), respectively. Salmonella strains were detected in 13 (36.1 %) irrigation water samples, while only two tomato samples were positive (5.5 %). Eight different serotypes were identified in irrigation water, and Salmonella Oranienburg (34 %) was the most prevalent; however, only Salmonella Agona and Salmonella Weltevreden were present on tomatoes. Salmonella Oranienburg was the most widely dispersed and variable serotype, with 10 different PFGE profiles. Salmonella Weltevreden was isolated from both types of samples, albeit with distinct genetic profiles, implying that the sources of contamination differ. These results confirm the utility of implementing good agricultural practices to reduce Salmonella contamination in irrigation water and the packaging process.

First detection and genotyping of human-associated microsporidia in wild waterfowl of Slovakia

A total of 47 avian faecal samples of wild waterfowl (great cormorant - Phalacrocorax carbo, great crested grebe - Podiceps cristatus, white stork - Ciconia ciconia) trapped in the eastern Slovakia were screened for the presence of human pathogenic microsporidia by microscopy and real-time SYBR Green PCR method using species primers and sequenced. Microscopic analysis showed presence in 32 samples (29 cormorants, 3 dippers). Microsporidial DNA (Encephalitozoon cuniculi genotype I) was identified in 19 faeces samples (40.4%) namely cormorants in 17 out of 40, one dipper of 5 and a stork out of 2. The present work describes three new host species of the bird population in microsporidium Encephalitozoon cuniculi genotype I which confirms the theory of low specificity of this species.

Epidemiology of Enterocytozoon bieneusi Infection in Humans

A review was conducted to examine published works that focus on the complex epidemiology of Enterocytozoon bieneusi infection in humans. Studies on the prevalence of these emerging microsporidian pathogens in humans, in developed and developing countries, the different clinical spectra of E. bieneusi intestinal infection in children, in different settings, and the risk factors associated with E. bieneusi infection have been reviewed. This paper also analyses the impact of the recent application of PCR-based molecular methods for species-specific identification and genotype differentiation has had in increasing the knowledge of the molecular epidemiology of E. bieneusi in humans. The advances in the epidemiology of E. bieneusi, in the last two decades, emphasize the importance of epidemiological control and prevention of E. bieneusi infections, from both the veterinary and human medical perspectives.

Giardia--from genome to proteome

In this review, the current status of genomic and proteomic research on Giardia is examined in terms of evolutionary biology, phylogenetic relationships and taxonomy. The review also describes how characterising genetic variation in Giardia from numerous hosts and endemic areas has provided a better understanding of life cycle patterns, transmission and the epidemiology of Giardia infections in humans, domestic animals and wildlife. Some progress has been made in relating genomic information to the phenotype of Giardia, and as a consequence, new information has been obtained on aspects of developmental biology and the host-parasite relationship. However, deficiencies remain in our understanding of pathogenesis and host specificity, highlighting the limitations of currently available genomic datasets.

Risk factors for Giardia infection among hospitalized children in Cuba

The risk factors associated with Giardia infection, in children hospitalized in Havana, Cuba, were recently explored. Children aged ≥5 years were more likely to be positive for Giardia infection than the younger children, with an odds ratio (OR) of 3·41 [95% confidence interval (CI) = 1·36-9·69]. The risk factors found to be associated with Giardia infection in univariate analyses were rural residence (OR = 3·01; CI = 1·23-7·35), belonging to a household that did not receive water from an aqueduct (OR = 3·27; CI = 1·21-8·91), drinking unboiled water (OR = 3·64; CI = 2·14-6·26), nail biting (OR = 3·47; CI = 1·97-6·08), eating unwashed vegetables raw (OR = 4·84; CI = 2·33-10·14), and a personal (OR = 3·23; CI = 1·58-6·59) or family history (OR = 3·96; CI = 1·53-10·47) of previous parasitic infection. In multivariate analyses, however, only two (modifiable) risk factors were found to be independently and significantly associated with Giardia infection: nail biting and eating unwashed vegetables raw. It therefore seems that, at least at the individual level, giardiasis-prevention activities in Havana should be focussed on health education to improve personal hygiene and food-related practices. If appropriately managed, the surveillance of drinking water and foodstuffs, for Giardia and other parasites, might also help to reduce the hospitalization of Cuban children.

Foodborne illness associated with Cryptosporidium and Giardia from livestock

Waterborne outbreaks caused by Cryptosporidium and Giardia are well documented, while the public health implications for foodborne illness from these parasites have not been adequately considered. Cryptosporidium and Giardia are common in domestic livestock, where young animals can have a high prevalence of infection, shedding large numbers of oocysts and cysts. Molecular epidemiological studies have advanced our knowledge on the distribution of Cryptosporidium and Giardia species and genotypes in specific livestock. This has enabled better source tracking of contaminated foods. Livestock generate large volumes of fecal waste, which can contaminate the environment with (oo)cysts. Evidence suggests that livestock, particularly cattle, play a significant role in food contamination, leading to outbreaks of cryptosporidiosis. However, foodborne giardiasis seems to originate primarily from anthroponotic sources. Foodborne cryptosporidiosis and giardiasis are underreported because of the limited knowledge of the zoonotic potential and public health implications. Methods more sensitive and cheaper are needed to detect the often-low numbers of (oo)cysts in contaminated food and water. As the environmental burden of Cryptosporidium oocysts and Giardia cysts from livestock waste increases with the projected increase in animal agriculture, public health is further compromised. Contamination of food by livestock feces containing Cryptosporidium oocysts and Giardia cysts could occur via routes that span the entire food production continuum. Intervention strategies aimed at preventing food contamination with Cryptosporidium and Giardia will require an integrated approach based on knowledge of the potential points of entry for these parasites into the food chain. This review examines the potential for foodborne illness from Cryptosporidium and Giardia from livestock sources and discusses possible mechanisms for prevention and control.

Detection of microsporidia in drinking water, wastewater and recreational rivers

Diarrhea is the main health problem caused by human-related microsporidia, and waterborne transmission is one of the main risk factors for intestinal diseases. Recent studies suggest the involvement of water in the epidemiology of human microsporidiosis. However, studies related to the presence of microsporidia in different types of waters from countries where human microsporidiosis has been described are still scarce. Thirty-eight water samples from 8 drinking water treatment plants (DWTPs), 8 wastewater treatment plants (WWTPs) and 6 recreational river areas (RRAs) from Galicia (NW Spain) have been analyzed. One hundred liters of water from DWTPs and 50 L of water from WWTPs and RRAs were filtered to recover parasites, using the IDEXX Filta-Max® system. Microsporidian spores were identified by Weber's stain and positive samples were analyzed by PCR, using specific primers for Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon cuniculi, and Encephalitozoon hellem. Microsporidia spores were identified by staining protocols in eight samples (21.0%): 2 from DWTPs, 5 from WWTPs, and 1 from an RRA. In the RRA sample, the microsporidia were identified as E. intestinalis. To the best of our knowledge, this is the first report of human-pathogenic microsporidia in water samples from DWTPs, WWTPs and RRAs in Spain. These observations add further evidence to support that new and appropriate control and regulations for drinking, wastewater, and recreational waters should be established to avoid health risks from this pathogen.

Detection of zoonotic intestinal parasites in public parks of Spain. Potential epidemiological role of microsporidia

Several studies have demonstrated that the soil of public parks presents an important source of infection which has a significant impact on public health. Children are the main group affected by accidentally ingestion of contaminated soil. This study was performed in order to identify the presence of zoonotic parasites in dog and cat faecal and soil samples from public parks of Madrid, Spain. Six hundred twenty-five and seventy-nine soil and faecal samples (presumably from dogs and cats) respectively were collected from 67 parks. Intestinal parasites were identified in 27 parks (40.3%), which were contamined with Giardia sp. (19.4%), microsporidia (19.4%), Toxocara spp. (16.4%), Cryptosporidium sp. (6%), Entamoeba histolytica (3%) and Ancylostomidae (3%). Combinations of two or more intestinal parasites were found in 11 parks, and it was common to find Giardia and microsporidia together in samples. Intestinal parasites were detected in 18% (112/625) of soil samples. The most frequent parasite species found in the examined soil samples were Toxocara spp. (16.4%), followed by Giardia sp. (4.5%) and Strongyloides sp. larvae (3%). The zoonotic parasites found in the 79 faecal samples were Giardia sp. (17.7%), Cryptosporidium sp. (9%), E. histolytica (2.5%), Trichuris vulpis (1.3%), Toxascaris leonina (1.3%) and microsporidia spores (28%). Microsporidia characterization by amplification of DNA confirmed 10 samples as positive, eight for E. bieneusi and two for E. hellem by PCR. The role of those parasites in the environment are discussed.

First reported foodborne outbreak associated with microsporidia, Sweden, October 2009

Microsporidia are spore-forming intracellular parasites that infrequently cause disease in immunocompetent persons. This study describes the first report of a foodborne microsporidiosis outbreak which affected persons visiting a hotel in Sweden. Enterocytozoon bieneusi was identified in stool samples from 7/11 case-patients, all six sequenced samples were genotype C. To confirm that this was not a chance finding, 19 stool samples submitted by healthy persons from a comparable group who did not visit the hotel on that day were tested; all were negative for microsporidia. A retrospective cohort study identified 135 case-patients (attack rate 30%). The median incubation period was 9 days. Consumption of cheese sandwiches [relative risk (RR) 4·1, 95% confidence interval (CI) 1·4–12·2] and salad (RR 2·1, 95% CI 1·1–4) were associated with illness. Both items contained pre-washed, ready-to-eat cucumber slices. Microsporidia may be an under-reported cause of gastrointestinal outbreaks; we recommend that microsporidia be explored as potential causative agents in food- and waterborne outbreaks, especially when no other organisms are identified.

Municipal wastewater treatment plants as removal systems and environmental sources of human-virulent microsporidian spores

Municipal wastewater treatment plants play a vital role in reducing the microbial load of sewage before the end-products are discharged to surface waters (final effluent) or local environments (biosolids). This study was to investigate the presence of human-virulent microsporidian spores (Enterocytozoon bieneusi, Encephalitozoon intestinalis, and Encephalitozoon hellem) and enterococci during treatment processes at four Irish municipal secondary wastewater treatment plants (plants A-D). Microsporidian abundance was significantly related to seasonal increase in water temperature. Plant A had the least efficient removal of E. intestinalis spores (32%) in wastewater, with almost 100% removal at other plants both in April and July. Some negative removal efficiencies were obtained for E. bieneusi (at plants C and D, -100%) and for E. hellem (at plants A and D, -90% and -50%). In addition, a positive correlation was found between the levels of enterococci and E. bieneusi in July (r (s) = 0.72, P < 0.05). In terms of the dewatered biosolids, a median concentration as high as 32,000 spores/Kg of E. hellem was observed at plant D in July. Plant C sewage sludge contained the lowest microsporidian loadings (E. bieneusi; 450 spores/L and 1,000 spores/L in April and July, respectively). This study highlights the seasonal variation in concentrations of microsporidian spores in the incoming sewage. Spores in final effluents and dewatered biosolids can be the source of human-virulent microsporidian contamination to the local environment. This emphasizes a considerably high public health risk when sewage-derived biosolids are spread during summer months. This study also suggested enterococci as a potential indicator of the presence of microsporidian spores in wastewater, especially for E. bieneusi.

Microbiological water quality in a large irrigation system: El Valle del Yaqui, Sonora México

The primary objective of this study was to determine the microbial water quality of a large irrigation system and how this quality varies with respect to canal size, impact of near-by communities, and the travel distance from the source in the El Valle del Yaqui, Sonora, México. In this arid region, 220,000 hectares are irrigated with 80% of the irrigation water being supplied from an extensive irrigation system including three dams on the Yaqui River watershed. The stored water flows to the irrigated fields through two main canal systems (severing the upper and lower Yaqui Valley) and then through smaller lateral canals that deliver the water to the fields. A total of 146 irrigation water samples were collected from 52 sample sites during three sampling events. Not all sites could be accessed on each occasion. All of the samples contained coliform bacteria ranging from 1,140 to 68,670 MPN/100 mL with an arithmetic mean of 11,416. Ninety-eight percent of the samples contained less than 1,000 MPN/100 mL Escherichia coli, with an arithmetic mean of 291 MPN/100 mL. Coliphage were detected in less than 30% of the samples with an arithmetic average equal to 141 PFU/100 mL. Enteroviruses, Cryptosporidium oocysts, and Giardia cysts were also detected in the canal systems. No significant difference was found in the water quality due to canal system (upper or lower Yaqui Valley), canal-size (main vs. lateral), distance from source, and the vicinity of human habitation (presence of various villages and towns along the length of the canals). There was a significant decrease in coliforms (p < 0.011) and E. coli (< 0.022) concentrations as travel distance increased from the City of Obregón.

Unapparent microsporidial infection among immunocompetent humans in the Czech Republic

In the present population-based study, we determined the prevalences of the most common human-pathogenic microsporidia, Encephalitozoon spp. and Enterocytozoon bieneusi, in asymptomatic healthy people living in the Czech Republic. A total of 382 males and females (ages, 1 to 84 years) living in the Czech Republic, of whom 265 were Czech nationals and 117 were foreign students, were included in a study testing for the presence of microsporidia by use of coprology and molecular methods. Single-species infections with Enterocytozoon bieneusi or an Encephalitozoon sp. were detected for 9 and 136 individuals, respectively. Moreover, coinfections were detected for 14 individuals. Four genotypes of 3 human-pathogenic Encephalitozoon spp. and 7 E. bieneusi genotypes, including 3 novel genotypes, were detected. Some of these were reported in humans for the first time. The highest prevalence was recorded for individuals older than 50 years and for loose, unformed stool samples. These findings clearly show that exposure to microsporidia is common among immunocompetent people and that microsporidiosis is not linked to any clinical manifestation in healthy populations.

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.

Spinacia oleracea L. leaf stomata harboring Cryptosporidium parvum oocysts: a potential threat to food safety

Cryptosporidium parvum is a cosmopolitan microscopic protozoan parasite that causes severe diarrheal disease (cryptosporidiosis) in mammals, including humans and livestock. There is growing evidence of Cryptosporidium persistence in fresh produce that may result in food-borne infection, including sporadic cases as well as outbreaks. However, drinking and recreational waters are still considered the major sources of Cryptosporidium infection in humans, which has resulted in prioritization of studies of parasite etiology in aquatic environments, while the mechanisms of transmission and parasite persistence on edible plants remain poorly understood. Using laser scanning confocal microscopy together with fluorescein-labeled monoclonal antibodies, C. parvum oocysts were found to strongly adhere to spinach plants after contact with contaminated water, to infiltrate through the stomatal openings in spinach leaves, and to persist at the mesophyll level. These findings and the fact that this pathogenic parasite resists washing and disinfection raise concerns regarding food safety.

Risk assessment of cryptosporidium and giardia in water irrigating fresh produce in Mexico

A rise in foodborne outbreaks in the United States associated with fresh produce has resulted in increased concerns with the importation of fruits and vegetables. Mexico is a major exporter of produce to the United States, particularly tomatoes and bell peppers. A quantitative microbial risk assessment (QMRA) was conducted to evaluate the public health impact of protozoan-laden water irrigating produce in Culiacan, Sinaloa, Mexico. Specifically, a QMRA was conducted to address the human health impact associated with consumption of tomatoes, bell peppers, cucumbers, and lettuce irrigated with water contaminated with Cryptosporidium and Giardia. Yearly infection risks were estimated and assumed a 120-day exposure in a given year. Annual risks range from 9 x 10(-6) for Cryptosporidium at the lowest concentration associated with bell peppers to almost 2 x 10(-1) for exposure to Giardia on lettuce at the highest detected concentration. With the relatively high number of illnesses resulting from produce-related outbreaks, addressing pre- and postharvest points of contamination for fruits and vegetables consumed raw should be a food industry priority. This research shows how QMRA can be used to interpret microbial contamination data for public health significance and subsequently provide the foundation for guideline development.

Cryptosporidium surveillance and risk factors in the United States

Surveillance for Cryptosporidium in the United States indicates that the reported incidence of infection has increased dramatically since 2004. The reasons for this increase are unclear but might be caused by an actual increase in incidence, improved surveillance, improved awareness about cryptosporidiosis, and/or increases in testing practices resulting from the licensing of the first-ever treatment for cryptosporidiosis. While regional differences remain, the incidence of cryptosporidiosis appears to be increasing across the United States. Onset of illness is most common during the summer, particularly among younger children. Cryptosporidiosis case reporting also influences outbreak detection and reporting; the recent rise in cases coincides with an increase in the number of reported cryptosporidiosis outbreaks, particularly in treated recreational water venues. Risk factors include ingesting contaminated recreational or drinking water, exposure to infected animals, having close contacts with cryptosporidiosis, travel to disease-endemic areas, and ingestion of contaminated food. Advances in molecular characterization of clinical specimens have improved our understanding of the changing epidemiology and risk factors. Prevention and control of cryptosporidiosis requires continued efforts to interrupt the transmission of Cryptosporidium through water, food, and contact with infected persons or animals. Of particular importance is continued improvement and monitoring of drinking water treatment and advances in the design, operation, and management of recreational water venues coupled with behavioral changes among the swimming public.