Comparison of viability assays for Cryptosporidium parvum oocysts after disinfection

Cryptosporidium parvum infection alters the intestinal mucosa transcriptome in neonatal calves: implications for immune function

One of the leading causes of infectious diarrhea in newborn calves is the apicomplexan protozoan Cryptosporidium parvum (C. parvum). However, little is known about its immunopathogenesis. Using next generation sequencing, this study investigated the immune transcriptional response to C. parvum infection in neonatal calves. Neonatal male Holstein-Friesian calves were either orally infected (N = 5) or not (CTRL group, N = 5) with C. parvum oocysts (gp60 subtype IIaA15G2R1) at day 1 of life and slaughtered on day 7 after infection. Total RNA was extracted from the jejunal mucosa for short read. Differentially expressed genes (DEGs) between infected and CTRL groups were assessed using DESeq2 at a false discovery rate < 0.05. Infection did not affect plasma immunohematological parameters, including neutrophil, lymphocyte, monocyte, leucocyte, thrombocyte, and erythrocyte counts as well as hematocrit and hemoglobin concentration on day 7 post infection. The immune-related DEGs were selected according to the UniProt immune system process database and were used for gene ontology (GO) and pathway enrichment analysis using Cytoscape (v3.9.1). Based on GO analysis, DEGs annotated to mucosal immunity, recognizing and presenting antigens, chemotaxis of neutrophils, eosinophils, natural killer cells, B and T cells mediated by signaling pathways including toll like receptors, interleukins, tumor necrosis factor, T cell receptor, and NF-KB were upregulated, while markers of macrophages chemotaxis and cytosolic pattern recognition were downregulated. This study provides a holistic snapshot of immune-related pathways induced by C. parvum in calves, including novel and detailed feedback and feedforward regulatory mechanisms establishing the crosstalk between innate and adaptive immune response in neonate calves, which could be utilized further to develop new therapeutic strategies.

In vitro cultivation methods for coccidian parasite research

The subclass Coccidia comprises a large group of protozoan parasites, including important pathogens of humans and animals such as Toxoplasma gondii, Neospora caninum, Eimeria spp., and Cystoisospora spp. Their life cycle includes a switch from asexual to sexual stages and is often restricted to a single host species. Current research on coccidian parasites focuses on cell biology and the underlying mechanisms of protein expression and trafficking in different life stages, host cell invasion and host-parasite interactions. Furthermore, novel anticoccidial drug targets are evaluated. Given the variety of research questions and the requirement to reduce and replace animal experimentation, in vitro cultivation of Coccidia needs to be further developed and refined to meet these requirements. For these purposes, established culture systems are constantly improved. In addition, new in vitro culture systems lately gained considerable importance in research on Coccidia. Well established and optimized in vitro cultures of monolayer cells can support the viability and development of parasite stages and even allow completion of the life cycle in vitro, as shown for Cystoisospora suis and Eimeria tenella. Furthermore, new three-dimensional cell culture models are used for propagation of Cryptosporidium spp. (close relatives of the coccidians), and the infection of three-dimensional organoids with T. gondii also gained popularity as the interaction between the parasite and host tissue can be studied in more detail. The latest advances in three-dimensional culture systems are organ-on-a-chip models, that to date have only been tested for T. gondii but promise to accelerate research in other coccidians. Lastly, the completion of the life cycle of C. suis and Cryptosporidium parvum was reported to continue in a host cell-free environment following the first occurrence of asexual stages. Such axenic cultures are becoming increasingly available and open new avenues for research on parasite life cycle stages and novel intervention strategies.

Bovine Cryptosporidium parvum field isolates differ in cytopathogenicity in HCT-8 monolayers

Suckling calves are prone to Cryptosporidium infection. The variable degree of clinical disease is influenced by keeping conditions and immune status of the host, but diversity of isolate virulence may also contribute. The aim of the current study was to evaluate the cytopathogenic effects of 26 C. parvum field isolates by using a MTT assay in HCT-8 cell monolayers. Cell viability of monolayers inoculated with oocysts of the field isolates varied considerably with values of 17.7% (± 5.1%) to 99.5% (± 7.1%). A standard deviation of 18.6% was detected for cell viability of the in house reference strain, which were tested alongside in every assay. Field isolates were grouped in three categories of cytopathogenicity. Probably the length of storage has an effect on the level of the cell destruction category detected post infection in vitro. The applied tool may help to better understand the variable course of cryptosporidiosis in the field.

Distribution of Cryptosporidium parvum gp60 subtypes in calf herds of Saxony, Germany

Cryptosporidiosis is a common protozoan parasitic infection that causes diarrhoea in neonatal calves. The high shedding of environmentally resistant oocysts facilitates outbreaks of cryptosporidiosis in humans. In total, 58 farms (512 calves) in Germany (Saxony and Brandenburg) were visited three times each. Faecal samples of pre-weaned calves were microscopically examined for oocysts of Cryptosporidium spp. using Heine staining and were scored with regard to their consistency. Overall, 88.9% of calves tested microscopically positive for Cryptosporidium spp. in at least one sample, and the excretion of oocysts was significantly (P < 0.01) associated with a higher faecal score (diarrhoea). After DNA extraction from pooled farm isolates, 47 samples were successfully subtyped by sequence analysis of the 60 kDa glycoprotein gene (gp60). All isolates belonged to subtype family IIa. IIaA15G2R1 was the most common subtype (present on 66% of the farms), followed by IIaA16G3R1 (13%). Subtypes IIaA14G1R1, IIaA14G2R1, IIaA1612R1, IIaA16G2R1, IIaA17G1R1, IIaA17G2R1, IIaA17G4R1 and IIaA19G2R1 were found sporadically. This is the first description of gp60 subtype IIaA17G4R1 in cattle in Germany.

Establishment of a germ carrier assay to assess disinfectant efficacy against oocysts of coccidian parasites

Parasites are a common threat to human and animal health. One option to combat parasites that produce infective environmental stages is to inactivate them by chemical disinfection. Standardised laboratory assays that enable proper evaluation of products suspected to be efficient are highly desirable to allow prudent selection and use of such potentially hazardous agents. Here, we present a newly developed in vitro germ carrier assay to evaluate inactivation of oocysts of the model organism Cryptosporidium parvum by chemical disinfectants. Stainless steel discs were used as carrier to mimic surface contamination by C. parvum oocysts. The germ carriers were incubated with approved chemical disinfectant for the specified time (2 h) and rinsed thereafter to remove the disinfectant and recover the exposed oocysts. Recovered oocysts were transferred to HCT-8 monolayers, and 48 h later, genomic DNA was extracted and quantified by real-time PCR targeting the hsp70 gene to estimate parasite reproduction. A panel of commercially available and approved disinfectants were examined and data compared with those of suspension assays and historical data obtained from efficacy assays based on infection of chicken with oocysts of Eimeria tenella. Altogether, data achieved by these divergent assays allowed similar conclusions although the sensitivity of the in vitro assay was higher. Consequently, a threshold of 99.5% inactivation is proposed to evaluate disinfectants in vitro using C. parvum as model organism as compared to the E. tenella animal infection assay (95%).

Efficacy of chlorine dioxide tablets on inactivation of cryptosporidium oocysts

The ability of chlorine dioxide (ClO2) to achieve 2-log inactivation of Cryptosporidium in drinking water has been documented. No studies have specifically addressed the effects of ClO2 on C. parvum oocyst infectivity in chlorinated recreational water venues (e.g., pools). The aim of this research was to determine the efficacy of ClO2 as an alternative to existing hyperchlorination protocols that are used to achieve a 3-log inactivation of Cryptosporidium in such venues. To obtain a 3-log inactivation of C. parvum Iowa oocysts, contact times of 105 and 128 min for a solution containing 5 mg/L ClO2 with and without the addition of 2.6 mg/L free chlorine, respectively, were required. Contact times of 294 and 857 min for a solution containing 1.4 mg/L ClO2 with and without the addition of 3.6 mg/L free chlorine, respectively, were required. The hyperchlorination control (21 mg/L free chlorine only) required 455 min for a 3-log inactivation. Use of a solution containing 5 mg/L ClO2 and solutions containing 5 or 1.4 mg/L ClO2 with the addition of free chlorine appears to be a promising alternative to hyperchlorination for inactivating Cryptosporidium in chlorinated recreational water venues, but further studies are required to evaluate safety constraints on use.

Case-control study of microbiological etiology associated with calf diarrhea

Calf diarrhea is a major economic burden for the US cattle industry. A variety of infectious agents are implicated in calf diarrhea and co-infection of multiple pathogens is not uncommon in diarrheic calves. A case–control study was conducted to assess infectious etiologies associated with calf diarrhea in Midwest cattle farms. A total of 199 and 245 fecal samples were obtained from diarrheic and healthy calves, respectively, from 165 cattle farms. Samples were tested by a panel of multiplex PCR assays for 11 enteric pathogens: bovine rotavirus group A (BRV-A), bovine coronavirus (BCoV), bovine viral diarrhea virus (BVDV), bovine enterovirus (BEV), bovine norovirus (BNoV), Nebovirus, bovine torovirus (BToV) Salmonella spp. (Salmonella), Escherichia coli (E. coli) K99⁺, Clostridium perfringens with β toxin gene and Cryptosporidium parvum (C. parvum). The association between diarrhea and detection of each pathogen was analyzed using a multivariate logistic regression model. More than a half of the fecal samples from the diarrheic calves had multiple pathogens. Statistically, BRV-A, BCoV, BNoV, Nebovirus, Salmonella, E. coli K99⁺, and C. parvum were significantly associated with calf diarrhea (p < 0.05). Among them, C. parvum and BRV-A were considered to be the most common enteric pathogens for calf diarrhea with high detection frequency (33.7% and 27.1%) and strong odds ratio (173 and 79.9). Unexpectedly BNoV (OR = 2.0) and Nebovirus (OR = 16.7) were identified with high frequency in diarrheic calves, suggesting these viruses may have a significant contribution to calf diarrhea.

Integration of halofuginone lactate treatment and disinfection with p-chloro-m-cresol to control natural cryptosporidiosis in calves

Two field studies were accomplished on a dairy farm in Saxony to compare different strategies for the control of natural cryptosporidiosis in newborn calves. In the first study, 96 newborn calves were allocated to four different groups immediately after birth. Calves of group H and of group HN were treated orally with 120 μg/kg body weight (BW) of halofuginone lactate daily during the first seven days of life. Calves of group C and of group CN were treated with a same volume of tap water. As an additional measure, the pens of groups HN and CN were disinfected with 3% Neopredisan 135-1^®(p-chloro-m-cresol), the pens of groups C and H remained non-disinfected. Faeces were examined semi-quantitatively for oocyst excretion using carbolfuchsin-staining and the clinical course was recorded. While disinfection alone (group CN) had no effect on oocyst shedding and diarrhoea, treatment with halofuginone lactate (groups H and HN) reduced oocyst shedding and diarrhoea significantly. Combination of treatment and disinfection (group HN) controlled cryptosporidiosis completely during the first two weeks after birth. However, prevalence of diarrhoea and oocyst shedding was higher in the third week of life in group HN than in any of the other groups. This delayed occurrence of cryptosporidiosis was not seen in study 2 when all calves were similarly protected by treatment and specific disinfection. Oocyst shedding was not observed in peripartal cows either by carbolfuchsin staining, ELISA or PCR.

Molecular identification of Giardia and Cryptosporidium from dogs and cats

The aim of the present study was to diagnose the presence of Giardia cysts and Cryptosporidium oocysts in household animals using nested polymerase chain reaction (PCR) and sequence analysis. One hundred faecal samples obtained from 81 dogs and 19 cats were investigated. The Cryptosporidium genotypes were determined by sequencing a fragment of the small subunit (SSU) rRNA gene, while the Giardia Assemblages were determined through analysis of the glutamate dehydrogenase (GDH) locus. Isolates from five dogs and two cats were positive by PCR for the presence of Giardia, and their sequences matched the zoonotic Assemblage A of Giardia. Cryptosporidium spp. isolated from one dog and one cat were both found to be C. parvum. One dog isolate harboured a mixed infection of C. parvum and Giardia Assemblage A. These findings support the growing evidence that household animals are potential reservoirs of the zoonotic pathogens Giardia spp. and Cryptosporidium spp. for infections in humans.

In vitro determination of anticryptosporidial activity of phytogenic extracts and compounds

Cryptosporidiosis caused by Cryptosporidium spp. is an important diarrhoeal disease observed in farm animals and humans, especially in young or immunocompromised individuals. A novel cell culture assay for testing extracts and pure compounds against Cryptosporidium parvum in 96-well microplate format was established and evaluated. It is based on previously described indirect fluorescent antibody techniques and was optimised for higher sample throughput. Rapid assessment of minimal inhibitory concentrations (MICs) was done by checking each well microscopically for the presence or absence of parasite stages. As a novelty, parasite development was quantified by enumeration of clusters of secondary infection (CSI), which typically appeared upon infection with a distinct parasite inoculum after a defined incubation time. Host cell (HCT-8) viability was measured by an integrated non-destructive water-soluble tetrazolium salt assay (WST-1), which facilitated discrimination of antiparasitic activity from possible cytotoxic effects of a test compound against the host cells. Host cell viability was regarded unimpaired when cultures had 75% or more viability when compared to control cultures without test substance. In this study, a maximum density of distinguishable CSI was obtained when cultures were infected with 2.5 × 10(3) oocysts and incubated for 48 h. The applicable inoculum has to be optimised for each batch of oocysts and before each experimental series. Parasite development was inhibited completely by monensin at 134 nM and silymarin at 50 mg/mL. These concentrations were non-toxic to the host cells and comparable to literature data. The percentages of parasite inhibition were determined for monensin and a 50% inhibitory concentration (IC(50)) of 36.6 nM (27.4-45.5) and a 90% inhibitory concentration of 65.9 nM (54.8-90.2) were calculated. The introduced assay is economic because relatively low parasite numbers may be used. If MICs are determined, evaluation is fast, as each well is viewed only briefly under the fluorescence microscope for presence or absence of CSI. Furthermore it is highly critical because only full parasite inhibition is assessed. Counting of CSI is more laborious and time-consuming, but it allows calculation of parasite inhibition rates and parameters like the half maximal inhibitory concentration (IC(50)). This assay shall be used to assess anticryptosporidial activities of various plant waste materials and by-products from the food and the pharmaceutical industries in the course of the EU project SAFEWASTES. Comparison with in vivo models should be performed to further corroborate the results. Automated evaluation by flow cytometry might facilitate higher sample throughput and reduce operator bias.

Comparison of assays for sensitive and reproducible detection of cell culture-infectious Cryptosporidium parvum and Cryptosporidium hominis in drinking water

This study compared the three most commonly used assays for detecting Cryptosporidium sp. infections in cell culture: immunofluorescent antibody and microscopy assay (IFA), PCR targeting Cryptosporidium sp.-specific DNA, and reverse transcriptase PCR (RT-PCR) targeting Cryptosporidium sp.-specific mRNA. Monolayers of HCT-8 cells, grown in 8-well chamber slides or 96-well plates, were inoculated with a variety of viable and inactivated oocysts to assess assay performance. All assays detected infection with low doses of flow cytometry-enumerated Cryptosporidium parvum oocysts, including infection with one oocyst and three oocysts. All methods also detected infection with Cryptosporidium hominis. The RT-PCR assay, IFA, and PCR assay detected infection in 23%, 25%, and 51% of monolayers inoculated with three C. parvum oocysts and 10%, 9%, and 16% of monolayers inoculated with one oocyst, respectively. The PCR assay was the most sensitive, but it had the highest frequency of false positives with mock-infected cells and inactivated oocysts. IFA was the only infection detection assay that did not produce false positives with mock-infected monolayers. IFA was also the only assay that detected infections in all experiments with spiked oocysts recovered from Envirochek capsules following filtration of 1,000 liters of treated water. Consequently, cell culture with IFA detection is the most appropriate method for routine and sensitive detection of infectious Cryptosporidium parvum and Cryptosporidium hominis in drinking water.

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.

Efficacy of amine-based disinfectant KENO™COX on the infectivity of Cryptosporidium parvum oocysts

Cryptosporidium parvum is a zoonotic protozoan parasite that may cause severe neonatal diarrhoea or even mortality in newborn ruminants: its oocysts are extremely resistant to normal environmental conditions and to most common disinfectants. KENO™COX, a patent pending amine-based formula, was tested for its ability to inactivate C. parvum oocysts. The Daugschies assay (2002), a standardized assay for chemical disinfection initially described for Eimeria spp., was adapted for C. parvum oocysts. KENO™COX diluted in water at 2% and 3% concentration and incubated with oocyst suspensions for 2h, allowed a significant reduction in viability, lysing 89% and 91% of oocysts respectively. Infectivity of the remaining C. parvum oocysts was assessed by inoculation to C57 Bl/6 neonatal mice. Each mouse received 2.5 μl of a suspension initially containing 500,000 oocysts before contact with KENO™COX. Six days post inoculation, the intestinal parasite load was significantly reduced by 97.5% with KENO™COX 2% compared to that of the mice inoculated with untreated parasites. KENO™COX 3% completely eliminated infectivity of oocysts. The number of oocysts remaining infectious in the inoculum treated with KENO™COX 2% was calculated from an inoculated dose-response curve: it was estimated at about 48.6 oocysts among the 500,000 oocysts initially treated corresponding to 99.99% of inhibition. These results demonstrate the high efficacy of KENO™COX against C. parvum oocysts. Combined with an appropriate method of cleaning, the application of KENO™COX may be a useful tool to reduce cryptosporidial infectious load on farm level.

Comparative efficacy of conventional primer sets in detection of Cryptosporidium parvum for diagnostic use

In this study, the sensitivity and specificity of different previously described primer sets for Cryptosporidium parvum detection by polymerase chain reaction (PCR) was evaluated. For this purpose, the primer sets defined by Cacciò et al. (FEMS Microbiol Lett 170(1):173-179, 1999) (tub), Widmer et al. (Appl Environ Microbiol 64(11):4477-4481, 1998) (btub) and Rochelle et al. (Appl Environ Microbiol 63:2029-2037, 1997) (cphsp), respectively, were used. Deoxyribonucleic acid (DNA) was isolated from three different sample materials: (1) from the faeces of an experimentally C. parvum-infected calf, (2) from purified C. parvum oocysts, and (3) from C. parvum-infected HCT-8 cell cultures. The DNA samples were subjected to PCR reactions with each of the three given primer sets to investigate sensitivity and suitability for routine use. The primers described by Cacciò et al. (FEMS Microbiol Lett 170(1):173-179, 1999) (TUB) were superior regarding sensitivity and specificity in terms of detection of C. parvum in faeces, in purified oocysts and also in cell culture, and may thus be applied for routine diagnostic use in common sample materials.

Combination of cell culture and quantitative PCR (cc-qPCR) to assess disinfectants efficacy on Cryptosporidium oocysts under standardized conditions

Oocysts of Cryptosporidium parvum are resistant to environmental conditions and many disinfectants. A combination of cell culture and quantitative real time PCR (cc-qPCR) is established for evaluation of anticoccidial disinfectants against C. parvum. C. parvum oocysts were treated with disinfectants, washed and oocysts were incubated with HCT-8 cell monolayers in the presence of excystation medium for 3h. Subsequently, unbound parasites were removed by washing with growing medium and the infected monolayers were further maintained in fresh growing medium for 48h. Genomic DNA was extracted from each sample and qPCR performed targeting a specific sequence of the 70kDa heat shock protein gene in order to quantify development. Treatment of oocysts with cresolic disinfectants demonstrated dose dependent reduction of viability of oocysts. More than 98% inactivations were recorded with at least 2% concentration of cresolic disinfectants after 2h of treatment. Bleach (sodium hypochlorite) at 6% solution induced 92.7% inactivation of C. parvum oocysts after 2h. Thermally treated oocysts (56 and 70 degrees C for 20min) demonstrated complete inactivation, whereas at 38 degrees C no inactivation was observed. Application of Neopredisan((R)) 135-1 and Aldecoc((R)) TGE (4% for 2h) as recommended according to the current guidelines stipulated by DVG (German Veterinary Society) consistently inactivated more than 99.5% of oocysts. The suggested cc-qPCR method appeared to be suited for standardized testing of inactivation measures, particularly for evaluation of chemical disinfectants and thus cc-qPCR is proposed as an alternative to the established chicken infectivity model for Eimeria tenella for testing anticoccidial disinfectants. A minimum inactivation of 99.5% in cc-qPCR model is claimed as a suitable threshold for certification of chemical products for disinfection of coccidia oocysts.

Inactivation of protozoan parasites in food, water, and environmental systems

Protozoan parasites can survive under ambient and refrigerated storage conditions when associated with a range of substrates. Consequently, various treatments have been used to inactivate protozoan parasites (Giardia, Cryptosporidium, and Cyclospora) in food, water, and environmental systems. Physical treatments that affect survival or removal of protozoan parasites include freezing, heating, filtration, sedimentation, UV light, irradiation, high pressure, and ultrasound. Ozone is a more effective chemical disinfectant than chlorine or chlorine dioxide for inactivation of protozoan parasites in water systems. However, sequential inactivation treatments can optimize existing treatments through synergistic effects. Careful selection of methods to evaluate inactivation treatments is needed because many studies that have employed vital dye stains and in vitro excystation have produced underestimations of the effectiveness of these treatments.

Evaluation of two commercial disinfectants on the viability and infectivity of Cryptosporidium parvum oocysts

Cryptosporidiosis is mainly a problem in neonatal ruminants. Not only do Cryptosporidium spp. spread ubiquitously in our environment, but the protozoa are highly resistant to harsh environmental conditions and disinfectants, and a control measure is urgently required. This study investigated the potential biocidal activity on Cryptosporidium parvum oocysts of two commercial disinfectants developed originally to be used in farms and food-processing industries. The products, containing formaldehyde and hydrogen peroxide respectively, both had some anticryptosporidial effects. The viability and infectivity of purified C. parvum oocysts exposed to both disinfectants at different concentrations and exposure times were evaluated by inclusion or exclusion of vital dye (propidium iodide), use of an excystation technique and infection of suckling mice. Viability assays showed a decrease in oocyst viability associated with an increase in exposure time for each of the concentrations used. The intensity of infection in neonatal mice was significantly lower (P<0.05) than in the control litters.

Development of a sensitive detection system for Cryptosporidium in environmental samples

The identification of Cryptosporidium species and genotypes is necessary to determine sources of infection in outbreaks and the risk factors associated with their transmission. Few studies have applied isolation methods to field samples because of difficulties with detection of oocysts in environmental samples, particularly in soil and manure. The objective of this study was to develop an easy to use method which can be applied to field samples to rapidly detect the presence of Cryptosporidium parasites and identify their species. The assay included an oocyst recovery method combined with spin column DNA extraction, followed by PCR-hybridization for detection and a real-time PCR-melting curve analysis for species assignment. An internal positive control (IPC) was developed to determine the presence of PCR inhibitory substances. Two oocyst recovery methods, sodium chloride and sucrose flotation techniques were compared. Two commercial DNA extraction kits were performed using feces, soil and water samples each inoculated with different concentration of Cryptosporidium oocysts. Subsequently, methods were used to test field samples. The sucrose flotation method provided the greatest analytical sensitivity detecting as few as 10 oocysts. The PCR-hybridization detection limit was 10 oocysts for feces and soil, and less than 10 oocysts for water samples. IPC was positive for all inoculated and field samples indicating 0% PCR inhibition. Cryptosporidium species DNA samples were detected with the real-time PCR and were differentiated by the melting curve analysis. The results of this study demonstrate the potential of the assay system for rapid detection of Cryptosporidium parasites in environmental samples.

Quantification of the infectivity of Cryptosporidium parvum by monitoring the oocyst discharge from SCID mice

Doses of 1-10(5) oocysts of Cryptosporidium parvum HNJ-1 were inoculated into severe combined immunodeficient (SCID) mice, and the discharge of oocysts was monitored for 30 days post inoculation. None of the mice discharged any oocysts after oral inoculation of one oocyst. Only one of five SCID mice discharged oocysts after oral inoculation of 10 oocysts, and the prepatent period was 17 days. The other four mice did not discharge any oocysts. All the SCID mice discharged oocysts after oral inoculation of 10(2)-10(5) oocysts. The prepatent periods were 13-17, 8-10, 8, and 10 days in SCID mice inoculated with 10(2), 10(3), 10(4), and 10(5) oocysts, respectively. A proportional correlation was observed between inoculation doses of oocysts ranging from 10 to 10(4) oocysts and the corresponding prepatent periods. The prepatent period can be used to evaluate the infectivity of C. parvum oocysts.

Validity of the indicator organism paradigm for pathogen reduction in reclaimed water and public health protection

The validity of using indicator organisms (total and fecal coliforms, enterococci, Clostridium perfringens, and F-specific coliphages) to predict the presence or absence of pathogens (infectious enteric viruses, Cryptosporidium, and Giardia) was tested at six wastewater reclamation facilities. Multiple samplings conducted at each facility over a 1-year period. Larger sample volumes for indicators (0.2 to 0.4 liters) and pathogens (30 to 100 liters) resulted in more sensitive detection limits than are typical of routine monitoring. Microorganisms were detected in disinfected effluent samples at the following frequencies: total coliforms, 63%; fecal coliforms, 27%; enterococci, 27%; C. perfringens, 61%; F-specific coliphages, approximately 40%; and enteric viruses, 31%. Cryptosporidium oocysts and Giardia cysts were detected in 70% and 80%, respectively, of reclaimed water samples. Viable Cryptosporidium, based on cell culture infectivity assays, was detected in 20% of the reclaimed water samples. No strong correlation was found for any indicator-pathogen combination. When data for all indicators were tested using discriminant analysis, the presence/absence patterns for Giardia cysts, Cryptosporidium oocysts, infectious Cryptosporidium, and infectious enteric viruses were predicted for over 71% of disinfected effluents. The failure of measurements of single indicator organism to correlate with pathogens suggests that public health is not adequately protected by simple monitoring schemes based on detection of a single indicator, particularly at the detection limits routinely employed. Monitoring a suite of indicator organisms in reclaimed effluent is more likely to be predictive of the presence of certain pathogens, and a need for additional pathogen monitoring in reclaimed water in order to protect public health is suggested by this study.

Evaluation of two rapid assays for detecting Cryptosporidium parvum in calf feces

OBJECTIVE

To evaluate 2 rapid, patient-side assays for detection of Cryptosporidium parvum in feces from neonatal calves with diarrhea.

DESIGN

Diagnostic test evaluation Sample Population-Fecal samples from 96 neonatal (1 to 30 days old) calves with diarrhea.

PROCEDURE

Results of the rapid assays were compared with results of microscopic examination of fecal smears that had been stained with diamant fuchsin stain.

RESULTS

One of the rapid assays correctly identified 56 of 62 (90%) fecal samples positive for C. parvum oocysts and 33 of 34 (97%) fecal samples negative for oocysts. The other assay correctly identified 53 of 62 (85%) fecal samples positive for oocysts and 33 of 34 (97%) fecal samples negative for oocysts.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that these 2 rapid assays are accurate when used to detect C. parvum in fecal samples from neonatal calves with diarrhea.

Structural analysis of Cryptosporidium parvum

Cryptosporidium parvum (Apicomplexa, formerly Sporozoa) is the causative agent of cryptosporidiosis, an enteric disease of substantial medical and veterinary importance. C. parvum shows a number of unique features that differ from the rest of the class of coccidea in which it is currently grouped taxonomically. Differences occur in the overall structure of the transmission form and the invasive stages of the parasite, its intracellular location, the presence of recently described additional extracellular stages, the host range and target cell tropism, the ability to autoinfection, the nonresponsiveness to anticoccidial drugs, the immune response of the host, and immunochemical and genetic characteristics. These differences have an important impact on the infectivity, the epidemiology, the therapy, and the taxonomy of the parasite. The present article describes the structural analysis of the parasite using light and electron microscopy with an emphasis on structural details unique to C. parvum.

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.