Estimating viability of Cryptosporidium parvum oocysts using reverse transcriptase-polymerase chain reaction (RT-PCR) directed at mRNA encoding amyloglucosidase

Cryptosporidium spp. CP15 and CSL protein-derived synthetic peptides' immunogenicity and in vitro seroneutralisation capability

Cryptosporidium spp. is a zoonotic intracellular protozoan and a significant cause of diarrhoea in humans and animals worldwide. This parasite can cause high morbidity in immunocompromised people and children in developing countries, livestock being the main reservoir. This study was aimed at performing preliminary tests on Swiss albino weaned mice (ICR) to evaluate the humoral immune response induced against peptides derived from Cryptosporidium parvum CP15 (15 kDa sporozoite surface antigen) and CSL (circumsporozoite-like antigen) proteins. Peptides were identified and characterised using bioinformatics tools and were chemically synthesised. The antibody response was determined and the neutralising effect of antibodies was measured in cell culture. Despite all peptides studied here were capable of stimulating antibody production, neutralising antibodies were detected for just two of the CP15-derived ones. Additional studies aimed at evaluating further the potential of such peptides as vaccine candidates are thus recommended.

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.

Cryptosporidium spp. Contamination in Perna perna Mussels Destined for Human Consumption in Southeastern Rio de Janeiro, Brazil

Cryptosporidium spp. has been recognized as an important pathogen. As bivalve mollusks are noted as potential sources of several pathogens due to their consumption as foodstuffs, the aim of this study was to investigate the occurrence of Cryptosporidium spp. oocysts in Perna perna mussels and in seawater samples from a mussel farm in Southeastern Brazil, where mussels are grown directly in the sea, attached to ropes. Oocysts were observed by microscopy and confirmed by an enzyme-linked immunosorbent assay. Oocysts were present in mussel gills and GI tracts, as well as in the seawater. Of the 100 females, 10% and 11% showed contaminated GI tracts and gills, respectively, while this rate was lower in males, at 5% and 8.9%. Oocysts were present in higher amounts in the GI tract compared to gills and water. Contamination of the study area is apparent, leading to public health risks. More in-depth studies are needed, including molecular investigations, to identify Cryptosporidium species in mussels, as well as the implementation of monitoring actions in animals destined for human consumption.

Assessment of the viability of Cryptosporidium parvum oocysts with the induction ratio of hsp70 mRNA production in manure

Determining the presence of viable Cryptosporidium parvum oocysts in complex environmental matrices in hygiene control can prevent the contamination of water resources and food with this pathogen. This study assessed the induction ratio of hsp70 mRNA production by heat shock in different oocysts as a marker of viability. Using different procedures for (m)RNA extraction directly from manure and reverse transcription real-time qPCR, this study found slightly increased hsp70 mRNA contents in viable oocysts that were heat shock induced at 45°C for 20 min compared to not induced oocysts (1.6 fold induction in average). Prolonging the heat shock treatment to 2h did not further increase the copy numbers. Heat shock by consecutive stimuli, such as freezing and then heating, did not yield significantly higher copy numbers than the 45°C treatment. There was a certain background level of hsp70 mRNA in viable oocysts that were not exposed to heat shock, indicating a constitutive production of the transcripts in the oocysts. The production of hsp70 mRNA induced by heat shock in oocysts aged for 9 months that exhibited reduced viability was lower than in fresher oocysts (induction ratio<1.2). No production of hsp70 mRNA by heat shock was detected in 12 months old oocysts that were not viable in the excystation test. Oocysts inactivated at 75°C for 30 min were not able to respond to heat shock, and low amount of copies were occasionally measured only in total RNA extracts, but not in mRNA extracts that were purified directly with an oligo (dT)25 based system. The induction ratio of hsp70 mRNA varied according to the viability of the organisms in a sample. Copy numbers of β-tubulin mRNA in viable oocysts were lower than hsp70 mRNA, therefore the latter is more suitable to detect low numbers of oocysts by RT-qPCR.

Comparison of propidium monoazide-quantitative PCR and reverse transcription quantitative PCR for viability detection of fresh Cryptosporidium oocysts following disinfection and after long-term storage in water samples

Purified oocysts of Cryptosporidium parvum were used to evaluate the applicability of two quantitative PCR (qPCR) viability detection methods in raw surface water and disinfection treated water. Propidium monoazide-qPCR targeting hsp70 gene was compared to reverse transcription (RT)-qPCR heat induced hsp70 mRNA in water samples spiked with oocysts. Changes in viability of flow cytometry sorted fresh and oocysts having undergone various aging periods (up to 48 months at 4 °C) were evaluated by Ct values obtained from the qPCR before and after disinfection scenarios involving ammonia or hydrogen peroxide. Both qPCR methods achieved stability in dose dependent responses by hydrogen peroxide treatment in distilled water that proved their suitability for the viability evaluations. Oocysts exposed to 3% hydrogen peroxide were inactivated at a rate of 0.26 h(-1) and 0.93 h(-1), as measured by the mRNA assay and the PMA-DNA assay, respectively. In contrast, the PMA-DNA assay was not as sensitive as the mRNA assay in detecting viability alterations followed by exposure to ammonia or after a long-term storage in 4 °C in distilled water since no dose response dependency was achieved. Surface water concentrates containing enhanced suspendable solids determined that changes in viability were frequently detected only by the mRNA method. Failure of, or inconsistency in the detection of oocysts viability with the PMA-DNA method, apparently resulted from solids that might have reduced light penetration through the samples, and thus inhibited the cross-linking step of PMA-DNA assay.

Detection of viable Cryptosporidium parvum in soil by reverse transcription-real-time PCR targeting hsp70 mRNA

Extraction of high-quality mRNA from Cryptosporidium parvum is a key step in PCR detection of viable oocysts in environmental samples. Current methods for monitoring oocysts are limited to water samples; therefore, the goal of this study was to develop a rapid and sensitive procedure for Cryptosporidium detection in soil samples. The efficiencies of five RNA extraction methods were compared (mRNA extraction with the Dynabeads mRNA Direct kit after chemical and physical sample treatments, and total RNA extraction methods using the FastRNA Pro Soil-Direct, PowerSoil Total RNA, E.Z.N.A. soil RNA, and Norgen soil RNA purification kits) for the direct detection of Cryptosporidium with oocyst-spiked sandy, loamy, and clay soils by using TaqMan reverse transcription-PCR. The study also evaluated the presence of inhibitors by synthesis and incorporation of an internal positive control (IPC) RNA into reverse transcription amplifications, used different facilitators (bovine serum albumin, yeast RNA, salmon DNA, skim milk powder, casein, polyvinylpyrrolidone, sodium hexametaphosphate, and Salmonella enterica serovar Typhi) to mitigate RNA binding on soil components, and applied various treatments (β-mercaptoethanol and bead beating) to inactivate RNase and ensure the complete lysis of oocysts. The results of spiking studies showed that Salmonella cells most efficiently relieved binding of RNA. With the inclusion of Salmonella during extraction, the most efficient mRNA method was Dynabeads, with a detection limit of 6 × 10(2) oocysts g(-1) of sandy soil. The most efficient total RNA method was PowerSoil, with detection limits of 1.5 × 10(2), 1.5 × 10(3), and 1.5 × 10(4) C. parvum oocysts g(-1) soil for sandy, loamy, and clay samples, respectively.

Cryptosporidium parvum oocyst viability and behaviour of the residual body during the excystation process

This study was conducted as a comparative evaluation of time-dependent changes in the viability of purified Cryptosporidium parvum oocysts by means of different excystation methods. Oocyst samples were 2 weeks to 12 months old and were treated with bile or sodium taurocholate, partly after pretreatment with hypochlorite. Pretreatment markedly enhanced the excystation of younger oocyst samples but did not increase excystation rates of 9 or 12-month-old oocysts. A cell culture-PCR assay was used as a second indicator for oocyst viability and was most consistent with excystation trials including oocyst pretreatment. In experiments aiming at the determination of the behaviour of the oocyst residual body during excystation, it could be demonstrated that it might be involved in this process.

Determining UV inactivation of Toxoplasma gondii oocysts by using cell culture and a mouse bioassay

The effect of UV exposure on Toxoplasma gondii oocysts has not been completely defined for use in water disinfection. This study evaluated UV-irradiated oocysts by three assays: a SCID mouse bioassay, an in vitro T. gondii oocyst plaque (TOP) assay, and a quantitative reverse transcriptase real-time PCR (RT-qPCR) assay. The results from the animal bioassay show that 1- and 3-log(10) inactivation is achieved with 4 mJ/cm(2) UV and 10 mJ/cm(2) low-pressure UV, respectively. TOP assay results, but not RT-qPCR results, correlate well with bioassay results. In conclusion, a 3-log(10) inactivation of T. gondii oocysts is achieved by 10-mJ/cm(2) low-pressure UV, and the in vitro TOP assay is a promising alternative to the mouse bioassay.

Cryptosporidium propidium monoazide-PCR, a molecular biology-based technique for genotyping of viable Cryptosporidium oocysts

Cryptosporidium is an important waterborne protozoan parasite that can cause severe diarrhea and death in the immunocompromised. The current methods used to monitor for Cryptosporidium oocysts in water are the microscopy-based USEPA methods 1622 and 1623. These methods assess total levels of oocysts in source waters, but do not determine oocyst viability or genotype. Recently, propidium monoazide (PMA) has been used in conjunction with molecular diagnostic tools to identify species and assess the viability of bacteria. The goal of this study was the development of a Cryptosporidium PMA-PCR (CryptoPMA-PCR) assay that includes PMA treatment prior to PCR analysis in order to prevent the amplification of DNA from dead oocysts. The results demonstrated that PMA penetrates only dead oocysts and blocks amplification of their DNA. The CryptoPMA-PCR assay can also specifically detect live oocysts within a mixed population of live and dead oocysts. More importantly, live oocysts, not dead oocysts, were detected in raw waste or surface water samples spiked with Cryptosporidium oocysts. This proof-of-concept study is the first to demonstrate the use of PMA for pre-PCR treatment of Cryptosporidium oocysts. The CryptoPMA-PCR assay is an attractive approach to specifically detect and genotype viable Cryptosporidium oocysts in the water, which is critical for human health risk assessment.

Evaluation of two methods for quantification of hsp70 mRNA from the waterborne pathogen Cryptosporidium parvum by reverse transcription real-time PCR in environmental samples

We optimized and evaluated two mRNA extraction methods to quantify induced hsp70 mRNA from viable and injured Cryptosporidium parvum oocysts by reverse transcription quantitative real-time PCR (RT-qPCR) in raw and treated manure. Methods based on guanidinium isothiocyanate/phenol/chloroform (GITC-PC) purification and direct mRNA extraction with magnetic oligo(dT)25-coated beads were evaluated for applicability and sensitivity. Both methods proved to be suitable for processing manure samples. With washed manure samples and oocyst disruption by bead beating for 165 s in time intervals with cumulative pooling of the lysate fractions, optimum RT-qPCR results were achieved. On average, 2.6 times more hsp70 mRNA was detected with the oligo(dT)25 method in comparison to the GITC-PC based method using fresh oocysts, whereas less mRNA was detected in aged oocysts. For fresh oocysts, analytical and method detection limits for the oligo(dT)25 based method were 1.7 cDNA copies/qPCR reaction and 5150 oocysts/mL manure, and for the GITC-PC based method 17 cDNA copies/qPCR reaction and 4950 oocysts/mL, respectively. In 12 months old oocysts with reduced viability, mRNA was occasionally detected only by the GITC-PC based method. Failure of or reduced detection with the oligo(dT)25 based method was apparently a result of weakened oocyst walls leading to quicker release of mRNA and therefore mRNA shredding by bead beating in the relatively long stretch between the capture sequence and the RT-qPCR target sites.

The role of free-ranging, captive, and domestic birds of Western Poland in environmental contamination with Cryptosporidium parvum oocysts and Giardia lamblia cysts

As Cryptosporidium parvum and Giardia lamblia can be disseminated in the environment by avian hosts, a total of 499 fecal dropping from 308 free-ranging, 90 captive, and 101 domestic birds were tested by conventional, immunological, and molecular techniques for these human enteropathogens. Twenty-six (5.2%) tested positive for G. lamblia cysts and 19 (3.8%) for C. parvum oocysts. A bird total of 23 (7.5%) free-ranging, two (2.2%) captive, and one (0.1%) domestic tested positive for cysts, whereas 18 (5.8%) free-ranging, one (1.1%) captive, and zero livestock birds tested positive for oocysts. G. lamblia cysts and C. parvum oocysts were found significantly more frequently in fecal droppings of free-ranging aquatic birds than in birds not normally associated with water. No specimen tested positive for both pathogens simultaneously. Aquatic birds represent an important epidemiologic link in water-associated transmission cycles of Cryptosporidium and Giardia and play a significant role in environmental contamination of aquatic habitats with these anthropozoonotic pathogens.

Occurrence of Cryptosporidium and Giardia in sewage sludge and solid waste landfill leachate and quantitative comparative analysis of sanitization treatments on pathogen inactivation

Circulation of Cryptosporidum and Giardia in the environment can be facilitated by spreading of sewage sludge on agricultural or livestock grazing lands or depositing in landfills. Solid waste landfill leachate and sewage sludge samples were quantitatively tested for C. parvum and C. hominis oocysts, and G. lamblia cysts by the combined multiplexed fluorescence in situ hybridization (FISH) and immunofluorescent antibody (IFA) method. Subsequently, the effects of four sanitization treatments (i.e., ultrasound and microwave energy disintegrations, and quicklime and top-soil stabilization) on inactivation of these pathogens were determined. The landfill leachate samples were positive for Giardia, and sewage sludge samples for both Cryptosporididium and Giardia. The overall concentration of G. lamblia cysts (mean; 24.2/g) was significantly higher (P<0.01) than the concentration of C. parvum and C. hominis oocysts (mean; 14.0/g). Sonication reduced the load of G. lamblia cysts to non-detectable levels in 12 of 21 samples (57.1%), and in 5 of 6 samples (83.3%) for C. parvum and C. hominis. Quicklime stabilization treatment was 100% effective in inactivation of Cryptosporidium and Giardia, and microwave energy disintegration lacked the efficacy. Top-soil stabilization treatment reduced gradually the load of both pathogens which was consistent with the serial dilution of sewage sludge with the soil substrate. This study demonstrated that sewage sludge and landfill leachate contained high numbers of potentially viable, human-virulent species of Cryptosporidium and Giardia, and that sonication and quicklime stabilization were the most effective treatments for sanitization of sewage sludge and solid waste landfill leachates.

CP2 gene as a useful viability marker for Cryptosporidium parvum

The validity of the CP2 gene of Cryptosporidium parvum as a viability marker was evaluated using absolute quantitative real-time polymerase chain reaction (qPCR) assays. Total ribonucleic acid (RNA) was isolated from live and heat-killed C. parvum oocysts, and complementary deoxyribonucleic acid was synthesized and used as a template. The most accurate number of viable C. parvum oocysts was predicted when the CP2 gene was used as a target gene. The lower detection limit of the CP2 gene was ten oocysts, which was the most sensitive among examined target genes. With heat shock induction, only hsp70 messenger RNA (mRNA) was induced, and the predicted viable oocyst number was increased by heat shock for this marker. The CP2, hsp70, Cryptosporidium oocyst wall protein, and beta-tubulin mRNAs were not detected in heat-killed oocysts, but the 18S ribosomal ribonucleic acid (rRNA) showed heat stability until 48 h after heat killing. Although the 18S rRNA demonstrated the fastest response in crossing point (CP) value among the examined primer sets in qPCR, overestimation of viable oocysts was noted in the analysis with this gene. In conclusion, the CP2 gene was identified as the most sensitive, reliable, and accurate candidate of a viability marker of C. parvum by qPCR evaluation.

Fecundity of Cryptosporidium parvum is correlated with intracellular levels of the viral symbiont CPV

Differences in the virulence and fecundity of Cryptosporidium parvum isolates have been observed by several researchers studying cryptosporidiosis. The purpose of the present study was to determine if there was a correlation between intracellular levels of the viral symbiont CPV in C. parvum and fecundity of two isolates of the parasite, namely C. parvum Beltsville (B) and C. parvum Iowa (I). Dairy calves infected with 10(6)C. parvum-B excreted 5-fold more oocysts compared with calves infected with the same number of C. parvum-I oocysts. The increased fecundity of the former strain was corroborated by semi-quantitative PCR assay of DNA isolated from cell cultures infected with either C. parvum-B or C. parvum-I. Quantitative reverse transcriptase-PCR analysis of viral RNA revealed a 3-fold greater number of CPV in C. parvum-B compared with C. parvum-I oocysts. These findings may indicate a role for CPV in fecundity and possibly virulence of C. parvum.

Cryptosporidium oocysts: challenging adversaries?

A recent review by Brendon King and Paul Monis once again puts Cryptosporidium oocysts under the spotlight. Why is this tough transmission stage so troublesome now? And are future environments likely to assist or hinder its apparent ubiquity? Here, we explore further the fascination and challenge engendered by this parasite transmission stage.

Critical processes affecting Cryptosporidium oocyst survival in the environment

Cryptosporidium are parasitic protozoans that cause gastrointestinal disease and represent a significant risk to public health. Cryptosporidium oocysts are prevalent in surface waters as a result of human, livestock and native animal faecal contamination. The resistance of oocysts to the concentrations of chlorine and monochloramine used to disinfect potable water increases the risk of waterborne transmission via drinking water. In addition to being resistant to commonly used disinfectants, it is thought that oocysts can persist in the environment and be readily mobilized by precipitation events. This paper will review the critical processes involved in the inactivation or removal of oocysts in the terrestrial and aquatic environments and consider how these processes will respond in the context of climate change.

Viability staining and animal infectivity of Cryptosporidium andersoni oocysts after long-term storage

Preservation of biological properties of oocysts during the storage is critical for experimental work. Stomach species of cryptosporidia are less resistant against external influences, and their infectivity decreases rapidly in comparison with intestinal cryptosporidia. Cryptosporidium andersoni oocysts lost their infectivity for gerbil (Meriones unguiculatus) after 7 months storage in deionised water (DW) or in 2.5% potassium dichromate solution (PDS). Evaluation of oocyst viability by flow cytometry indicates higher percentage of viable oocysts stored in PDS than in DW, particularly after 6 months of storage. However, direct counting using fluorescent microscope revealed that these results are false and are influenced by the change of staining properties during the storage in PDS. Moreover, the examination of oocyst integrity by flow cytometry revealed that oocysts preserved in PDS kept their wall integrity longer than those stored in DW, and this fact should be taken into consideration during quantification of oocyst survival.

Fluorescent in situ hybridization as a tool to retrospectively identify Cryptosporidium parvum and Giardia lamblia in samples from terrestrial mammalian wildlife

Fecal samples of five terrestrial mammalian wildlife species stored at 4 degrees C or at -20 degrees C for up to 36 months have been tested for human zoonotic enteric parasites (i.e., Cryptosporidium parvum and Giardia lamblia) using combined fluorescent in situ hybridization (FISH) and direct fluorescent antibody techniques. The prevalence of C. parvum and G. lamblia varied from 20 to 63% (mean, 45.8%) and from 13 to 100% (mean, 53.2%), respectively. The prevalence of C. parvum and G. lamblia infections was higher in small rodents (mean, 68.5%) than in other wildlife (mean, 21%). Overall, 31.1% of animals were coinfected, and coinfections were more prevalent in small rodents (mean, 52%) than in other wildlife species (mean, 13.2%). The present study has shown that the FISH assay can be retrospectively applied to fecal samples for the identification of C. parvum oocysts, but is less suitable for the identification of G. lamblia cysts in such samples. Terrestrial mammalian wildlife, particularly small rodents, can contribute to watershed contamination with C. parvum oocysts and G. lamblia cysts. To control contamination, the management of pristine watersheds used for drinking water purposes should incorporate control measures for terrestrial wildlife, especially field rodents residing within such watersheds.

Quantitative assessment of viable Cryptosporidium parvum load in commercial oysters (Crassostrea virginica) in the Chesapeake Bay

The epidemiological importance of increasing reports worldwide on Cryptosporidium contamination of oysters remains unknown in relation to foodborne cryptosporidiosis. Thirty market-size oysters (Crassostrea virginica), collected from each of 53 commercial harvesting sites in Chesapeake Bay, MD, were quantitatively tested in groups of six for Cryptosporidium sp. oocysts by immunofluorescent antibody (IFA). After IFA analysis, the samples were retrospectively retested for viable Cryptosporidium parvum oocysts by combined fluorescent in situ hybridization (FISH) and IFA. The mean cumulative numbers of Cryptosporidium sp. oocysts in six oysters (overall, 42.1+/-4.1) were significantly higher than in the numbers of viable C. parvum oocysts (overall, 28.0+/-2.9). Of 265 oyster groups, 221 (83.4%) contained viable C. parvum oocysts, and overall, from 10-32% (mean, 23%) of the total viable oocysts were identified in the hemolymph as distinct from gill washings. The amount of viable C. parvum oocysts was not related to oyster size or to the level of fecal coliforms at the sampling site. This study demonstrated that, although oysters are frequently contaminated with oocysts, the levels of viable oocysts may be too low to cause infection in healthy individuals. FISH assay for identification can be retrospectively applied to properly stored samples.

Recovery, bioaccumulation, and inactivation of human waterborne pathogens by the Chesapeake Bay nonnative oyster, Crassostrea ariakensis

The introduction of nonnative oysters (i.e., Crassostrea ariakensis) into the Chesapeake Bay has been proposed as necessary for the restoration of the oyster industry; however, nothing is known about the public health risks related to contamination of these oysters with human pathogens. Commercial market-size C. ariakensis triploids were maintained in large marine tanks with water of low (8-ppt), medium (12-ppt), and high (20-ppt) salinities spiked with 1.0 x 10(5) transmissive stages of the following human pathogens: Cryptosporidium parvum oocysts, Giardia lamblia cysts, and microsporidian spores (i.e., Encephalitozoon intestinalis, Encephalitozoon hellem, and Enterocytozoon bieneusi). Viable oocysts and spores were still detected in oysters on day 33 post-water inoculation (pwi), and cysts were detected on day 14 pwi. The recovery, bioaccumulation, depuration, and inactivation rates of human waterborne pathogens by C. ariakensis triploids were driven by salinity and were optimal in medium- and high-salinity water. The concentration of human pathogens from ambient water by C. ariakensis and the retention of these pathogens without (or with minimal) inactivation and a very low depuration rate provide evidence that these oysters may present a public health threat upon entering the human food chain, if harvested from polluted water. This conclusion is reinforced by the concentration of waterborne pathogens used in the present study, which was representative of levels of infectious agents in surface waters, including the Chesapeake Bay. Aquacultures of nonnative oysters in the Chesapeake Bay will provide excellent ecological services in regard to efficient cleaning of human-infectious agents from the estuarine waters.

Environmental temperature controls Cryptosporidium oocyst metabolic rate and associated retention of infectivity

Cryptosporidium is a significant cause of water-borne enteric disease throughout the world and represents a challenge to the water industry and a threat to public health. In this study we report the use of a cell culture-TaqMan PCR assay to measure oocyst inactivation rates in reagent-grade and environmental waters over a range of temperatures. While oocysts incubated at 4 degrees C and 15 degrees C remained infective over the 12-week holding period, we observed a 4 log(10) reduction in infectivity for both 20 and 25 degrees C incubation treatments at 12 and 8 weeks, respectively, for all water types examined, a faster rate of inactivation for oocysts than previously reported. This temperature-dependent inactivation was further investigated using a simple and rapid ATP assay described herein. Time course experiments performed in reagent-grade water at incubation temperatures of 4, 15, 20, 25, 30, and 37 degrees C identified a close relationship between oocyst infectivity and oocyst ATP content, demonstrating that temperature inactivation at higher temperatures is a function of increased oocyst metabolic activity. While water quality did not affect oocyst inactivation, biological antagonism appears to be a key factor affecting oocyst removal from environmental waters. Both the cell culture-TaqMan PCR assay and the ATP assay provide a sensitive and quantitative method for the determination of environmental oocyst inactivation, providing an alternative to the more costly and time-consuming mouse infection assay. The findings presented here relating temperature to oocyst inactivation provide valuable information for determining the relative risks associated with Cryptosporidium oocysts in water.

Amylopectin: a major component of the residual body in Cryptosporidium parvum oocysts

Amylopectin is used for carbohydrate storage in different life-stages of a number of apicomplexan parasites. We have performed an ultrastructural analysis of amylopectin granules from the oocyst residual body and sporozoites of Cryptosporidium parvum. Amylopectin granules were studied in situ and after isolation from 'French' press disrupted parasites, by conventional transmission electron microscopy (TEM) of sectioned oocysts and various negative staining and cryoelectron microscopy techniques. Within the membrane-enclosed oocyst residuum large amylopectin granules (0.1-0.3 microm) can be found besides a characteristic large lipid body and a crystalline protein inclusion. Smaller granules were detected in sectioned sporozoites. Negative staining of isolated amylopectin granules revealed some ultrastructural features not readily visible in sectioned material. The large amylopectin granules had a smooth surface with a 'ball of string'-like inner structure. Granules isolated from sporozoites were more irregularly shaped and showed a rod-like particulate composition. With the exception of alpha-amylase, which led to some degree of damage of the surface of the particles, treatment of amylopectin granules with other glycohydrolases had little effect on the overall structure. However, granules adhered to one another. Only when the granules were boiled did the 'ball of string' structure gradually dissolve.

Cryptosporidium parvum and Giardia lamblia recovered from flies on a cattle farm and in a landfill

Filth flies associated with a cattle barn and a municipal landfill were tested positive by combined immunofluorescent antibody and fluorescent in situ hybridization for Cryptosporidium parvum and Giardia lamblia on their exoskeletons and in their guts. More pathogens were carried by flies from the cattle barn than from the landfill; 81% of C. parvum and 84% of G. lamblia pathogens were presumptively viable.

Biology, persistence and detection of Cryptosporidium parvum and Cryptosporidium hominis oocyst

Cryptosporidium parvum and Cryptosporidium hominis are obligate enteric protozoan parasites which infect the gastrointestinal tract of animals and humans. The mechanism(s) by which these parasites cause gastrointestinal distress in their hosts is not well understood. The risk of waterborne transmission of Cryptosporidium is a serious global issue in drinking water safety. Oocysts from these organisms are extremely robust, prevalent in source water supplies and capable of surviving in the environment for extended periods of time. Resistance to conventional water treatment by chlorination, lack of correlation with biological indicator microorganisms and the absence of adequate methods to detect the presence of infectious oocysts necessitates the development of consistent and effective means of parasite removal from the water supply. Additional research into improving water treatment and sewage treatment practices is needed, particularly in testing the efficiency of ozone in oocyst inactivation. Timely and efficient detection of infectious C. parvum and C. hominis oocysts in environmental samples requires the development of rapid and sensitive techniques for the concentration, purification and detection of these parasites. A major factor confounding proper detection remains the inability to adequately and efficiently concentrate oocysts from environmental samples, while limiting the presence of extraneous materials. Molecular-based techniques are the most promising methods for the sensitive and accurate detection of C. parvum and C. hominis. With the availability of numerous target sequences, RT-PCR will likely emerge as an important method to assess oocyst viability. In addition, a multiplex PCR for the simultaneous detection of C. parvum, C. hominis and other waterborne pathogens such as Giardia lamblia would greatly benefit the water industry and protect human health.

Viability and infectivity of Cryptosporidium parvum oocysts detected in river water in Hokkaido, Japan

The viability and infectivity of Cryptosporidium parvum (C. parvum) oocysts, detected in water samples collected from river water in Hokkaido, were investigated using Severe Combined Immunodeficient (SCID) mice. The water samples collected from September 27 through October 10, 2001 by filtration using Cuno cartridge filters were purified and concentrated by the discontinuous centrifugal flotation method. From 1.2 x 10 (5) liters of the raw river water, approximately 2 x 10(4) oocysts were obtained and designated as Hokkaido river water 1 isolate (HRW-1). Oocyst identification was carried out using microscopic and immunological methods. Six 8-week-old female SCID mice were each inoculated orally with 1 x 10 (3) oocysts. Infection was successfully induced, resulting in fecal oocyst shedding. Oocysts were then maintained by sub-inoculation into SCID mice every 3 months. Infectivity was evaluated by making comparisons with two known C. parvum stocks, HNJ-1 and TK-1, which were bovine genotypes detected in fecal samples from a cryptosporidiosis patient and young cattle raised in Tokachi, Hokkaido respectively. The oocyst genotypes were determined from a small subunit ribosomal RNA (SSU-rRNA) gene by polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) analysis. No significant differences were observed in the average number of oocysts per gram of feces (OPG) in any of the isolates. Our data indicates that the C. parvum oocysts detected in the sampled river water were of C. parvum genotype 2. Moreover, our data on the continued isolation, detection and identification of the C. parvum isolates is consistent with the available epidemiological data for the Tokachi area.

Emerging waterborne infections: contributing factors, agents, and detection tools

Because microorganisms are easily dispersed, display physiological diversity, and tolerate extreme conditions, they are ubiquitous and may contaminate and grow in water. The presence of waterborne enteric pathogens (bacteria, viruses, and protozoa) in domestic water supplies represents a potentially significant human health risk. Even though major outbreaks of waterborne disease are comparatively rare, there is substantial evidence that human enteric pathogens that are frequently present in domestic water supplies are responsible for low-level incidence of waterborne microbial disease. Although these diseases are rarely debilitating to healthy adults for more than a few hours to a few days, enteric pathogens can cause severe illness, even death, for young children, the elderly, or those with compromised immune systems. As the epidemiology of waterborne diseases is changing, there is a growing global public health concern about new and reemerging infectious diseases that are occurring through a complex interaction of social, economic, evolutionary, and ecological factors. New microbial pathogens have emerged, and some have spread worldwide. Alternative testing strategies for waterborne diseases should significantly improve the ability to detect and control the causative pathogenic agents. In this article, we provide an overview of the current state of knowledge of waterborne microbial pathogens, their detection, and the future of new methods in controlling these infectious agents.

Direct detection of Cryptosporidium parvum oocysts by immunomagnetic separation-polymerase chain reaction in raw milk

Cryptosporidium parvum is an emerging protozoan parasite responsible for several serious outbreaks of cryptosporidiosis, an enteric infection characterized by severe intestinal distress. This parasite can be transmitted through contaminated water and raw food in the oocyst form, which is resistant to many environmental stresses and food processes. C. parvum is also commonly found on dairy farms and could be transmitted to humans through contaminated raw milk and dairy products. Thus, an immunomagnetic separation-polymerase chain reaction assay for direct detection of C. parvum oocysts in milk was developed. The procedure was able to detect < 10 C. parvum oocysts. Thus, it could be used for monitoring milk samples.

Cryptosporidium parvum and Cyclospora cayetanensis: a review of laboratory methods for detection of these waterborne parasites

Cryptosporidium and Cyclospora are obligate, intracellular, coccidian protozoan parasites that infest the gastrointestinal tract of humans and animals causing severe diarrhea illness. In this paper, we present an overview of the conventional and more novel techniques that are currently available to detect Cryptosporidium and Cyclospora in water. Conventional techniques and new immunological and genetic/molecular methods make it possible to assess the occurrence, prevalence, virulence (to a lesser extent), viability, levels, and sources of waterborne protozoa. Concentration, purification, and detection are the three key steps in all methods that have been approved for routine monitoring of waterborne oocysts. These steps have been optimized to such an extent that low levels of naturally occurring Cryptosporidium oocysts can be efficiently recovered from water. The filtration systems developed in the US and Europe trap oocysts more effectively and are part of the standard methodologies for environmental monitoring of Cryptosporidium oocysts in source and treated water. Purification techniques such as immunomagnetic separation and flow cytometry with fluorescent activated cell sorting impart high capture efficiency and selective separation of oocysts from sample debris. Monoclonal antibodies with higher avidity and specificity to oocysts in water concentrates have significantly improved the detection and enumeration steps. To date, PCR-based detection methods allow us to differentiate the human pathogenic Cryptosporidium parasites from those that do not infect humans, and to track the source of oocyst contamination in the environment. Cell culture techniques are now used to examine oocyst viability. While fewer studies have focused on Cyclospora cayetanensis, the parasite has been successfully detected in drinking water and wastewater using current methods to recover Cryptosporidium oocysts. More research is needed for monitoring of Cyclospora in the environment. Meanwhile, molecular methods (e.g. molecular markers such as intervening transcribed spacer regions), which can identify different genotypes of C. cayetanensis, show good promise for detection of this emerging coccidian parasite in water.

Occurrence and molecular genotyping of Cryptosporidium spp. in surface waters in Northern Ireland

AIMS

To investigate the incidence and genotype of Cryptosporidium parvum oocysts in drinking water sources in Northern Ireland for the period 1996-1999, and to compare conventional and molecular methods of detection.

METHODS AND RESULTS

Four hundred and seventy-four waters were investigated by conventional methods, namely immuno-fluorescent antibody detection (IFA; 380) and immuno-magnetic separation-IFA (IMS-IFA; 94), of which 14/474 (3%) were positive. Two hundred and fourteen samples (214/474) were also investigated by PCR techniques, targeting both the 18S rRNA and TRAP-C2 genes, of which 11/214 (5.1%) were positive. These 11 samples were classified as genotype II following sequence analysis of the TRAP-C2 amplicon.

CONCLUSIONS

This study demonstrated the low incidence of oocysts of C. parvum in water sources in Northern Ireland.

SIGNIFICANCE AND IMPACT OF THE STUDY

Such molecular-based techniques offer a number of advantages over conventional detection methodologies, namely greater sensitivity and specificity as well as the ability to provide accurate genotyping data rapidly, which may be valuable in directing operational management in potential outbreak situations.

Epidemiology of Cryptosporidium: transmission, detection and identification

There are 10 valid species of Cryptosporidium and perhaps other cryptic species hidden under the umbrella of Cryptosporidium parvum. The oocyst stage is of primary importance for the dispersal, survival, and infectivity of the parasite and is of major importance for detection and identification. Because most oocysts measure 4-6 microm, appear nearly spherical, and have obscure internal structures, there are few or no morphometric features to differentiate species and in vitro cultivation does not provide differential data as for bacteria. Consequently, we rely on a combination of data from three tools: morphometrics, molecular techniques, and host specificity. Of 152 species of mammals reported to be infected with C. parvum or an indistinguishable organism, very few oocysts have ever been examined using more than one of these tools. This paper reviews the valid species of Cryptosporidium, their hosts and morphometrics; the reported hosts for the human pathogen, C. parvum; the mechanisms of transmission; the drinking water, recreational water, and food-borne outbreaks resulting from infection with C. parvum; and the microscopic, immunological, and molecular methods used to detect and identify species and genotypes.