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

Detection of Cryptosporidium spp. and Giardia spp. in Environmental Water Samples: A Journey into the Past and New Perspectives

Among the major issues linked with producing safe water for consumption is the presence of the parasitic protozoa Cryptosporidium spp. and Giardia spp. Since they are both responsible for gastrointestinal illnesses that can be waterborne, their monitoring is crucial, especially in water sources feeding treatment plants. Although their discovery was made in the early 1900s and even before, it was only in 1999 that the U.S. Environmental Protection Agency (EPA) published a standardized protocol for the detection of these parasites, modified and named today the U.S. EPA 1623.1 Method. It involves the flow-through filtration of a large volume of the water of interest, the elution of the biological material retained on the filter, the purification of the (oo)cysts, and the detection by immunofluorescence of the target parasites. Since the 1990s, several molecular-biology-based techniques were also developed to detect Cryptosporidium and Giardia cells from environmental or clinical samples. The application of U.S. EPA 1623.1 as well as numerous biomolecular methods are reviewed in this article, and their advantages and disadvantages are discussed guiding the readers, such as graduate students, researchers, drinking water managers, epidemiologists, and public health specialists, through the ever-expanding number of techniques available in the literature for the detection of Cryptosporidium spp. and Giardia spp. in water.

Giardia and Cryptosporidium spp. dissemination during wastewater treatment and comparative detection via immunofluorescence assay (IFA), nested polymerase chain reaction (nested PCR) and loop mediated isothermal amplification (LAMP)

Environmental water samples from the Lower Rhine area in Germany were investigated via immunofluorescence assays (IFAs), nested polymerase chain reaction (nested PCR) and loop-mediated isothermal amplification (LAMP) to detect the presence of Giardia spp. (n=185) and Cryptosporidium spp. (n=227). The samples were concentrated through filtration or flocculation, and oocysts were purified via centrifugation through a sucrose density gradient. For all samples, IFA was performed first, followed by DNA extraction for the nested PCR and LAMP assays. Giardia cysts were detected in 105 samples (56.8%) by IFA, 62 samples (33.5%) by nested PCR and 79 samples (42.7%) by LAMP. Cryptosporidium spp. were detected in 69 samples (30.4%) by IFA, 95 samples (41.9%) by nested PCR and 99 samples (43.6%) by LAMP. According to these results, the three detection methods are complementary for monitoring Giardia and Cryptosporidium in environmental waters.

A whole water catchment approach to investigating the origin and distribution of Cryptosporidium species

AIMS

Investigating the distribution and origin of Cryptosporidium species in a water catchment affected by destocking and restocking of livestock as a result of a foot and mouth disease epidemic.

METHODS AND RESULTS

Surface water, livestock and wildlife samples were screened for Cryptosporidium and oocysts characterised by sequencing SSU rRNA and COWP loci, and fragment analysis of ML1, ML2 and GP60 microsatellite loci. Oocyst concentrations in water samples (0-20.29 per 10 l) were related to rainfall events, amount of rainfall and topography. There was no detectable impact from catchment restocking. Cryptosporidium spp. found in water were indicative of livestock (Cryptosporidium andersoni and Cryptosporidium parvum) and wildlife (novel genotypes) sources. However, C. andersoni was not found in any animals sampled. Calf infections were age related; C. parvum was significantly more common in younger animals (<4 weeks old). Older calves shared Cryptosporidium bovis, Cryptosporidium ryanae and C. parvum. Wildlife shed C. parvum, Cryptosporidium ubiquitum, muskrat genotype II and deer genotype.

CONCLUSIONS

Several factors affect the occurrence of Cryptosporidium within a catchment. In addition to farmed and wild animal hosts, topography and rainfall patterns are particularly important.

SIGNIFICANCE AND IMPACT OF THE STUDY

These factors must be considered when undertaking risk-based water safety plans.

Cryptosporidium: detection in water and food

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

Fate of Cryptosporidium parvum and Cryptosporidium hominis oocysts and Giardia duodenalis cysts during secondary wastewater treatments

This study investigates the fate of Cryptosporidium parvum and C. hominis oocysts and Giardia duodenalis cysts at four Irish municipal wastewater treatment plants (i.e., Plant A, B, C, and D) that utilize sludge activation or biofilm-coated percolating filter systems for secondary wastewater treatment. The fate of these pathogens through the sewage treatment processes was determined based on their viable transmissive stages, i.e., oocysts for Cryptosporidium and cysts for Giardia. Analysis of final effluent indicated that over 97% of viable oocysts and cysts were eliminated, except at Plant C, which achieved only 64% of oocyst removal. A significant correlation between the removal of oocysts and cysts was found at Plants A, B, and D (R = 0.98, P < 0.05). All sewage sludge samples were positive for C. parvum and C. hominis, and G. duodenalis, with maximum concentrations of 20 oocysts and eight cysts per gram in primary sludge indicating the need for further sludge sanitization treatments. This study provides evidence that C. parvum and C. hominis oocysts and G. duodenalis cysts are present throughout the wastewater processes and in end-products, and can enter the aquatic environment with consequent negative implications for public health.

Prevalence of Giardia and Cryptosporidium spp in calves from a region in New Zealand experiencing intensification of dairying

AIM

To investigate the prevalence of Giardia and Cryptosporidium spp in calves born during two spring-calving seasons in a rapidly intensifying dairying region in the South Island; to evaluate potential correlations between the prevalence of the organism and age, characteristics of faeces, and animal-housing practices; and to compare the results with those from established dairying regions in the North Island.

METHODS

A longitudinal study was conducted in 2005 and 2006 on 10 dairy farms located in the Otago region, South Island, New Zealand. A total of 1,190 faecal samples were collected from calves 1-7 weeks old. Direct immunofluorescent microscopy was used to screen the faecal samples for Giardia cysts and Cryptosporidium oocysts. The prevalence of Giardia and Cryptosporidium spp detected in calves in Otago was compared with that previously measured in calves from dairying regions in the Waikato and Manawatu, in the North Island .

RESULTS

On average, Giardia and Cryptosporidium spp were detected in 31% and 2.6% of all samples, respectively. The prevalence of Giardia spp cysts in faeces was higher in calves >or=3 weeks of age in 2005 (p<or=0.02) and in calves >or=2 weeks of age in 2006 (p=0.07) than in younger calves. No age-related pattern was observed for Cryptosporidium spp in either year. No correlations were evident between characteristics of faeces or animal housing practices and the prevalence of either organism, which did not differ between the two dairy farming regions.

CONCLUSIONS

Prevalence rates of Giardia and Cryptosporidium spp in calves 1-7 weeks old did not differ between the two geographical regions, nor did the regions' distinct climate conditions appear to influence the prevalence of either pathogen. Considering data from both years together, the presence of Giardia spp cysts in faeces appeared to increase in the first week or two after birth, so that, on average, 30-40% of animals from 3-6 weeks of age were affected.

CLINICAL RELEVANCE

This is the first study to report the prevalence of Giardia and Cryptosporidium spp in dairy calves in the South Island of New Zealand.

Specific and genotypic identification of Cryptosporidium from a broad range of host species by nonisotopic SSCP analysis of nuclear ribosomal DNA

The accurate identification of Cryptosporidium (Protozoa: Apicomplexa) species and genotypes is central to the understanding of the transmission and to the diagnosis and control of cryptosporidiosis. In this study, we demonstrate the effectiveness of nonisotopic SSCP analysis of a approximately 300 bp region of the small subunit (pSSU) of ribosomal DNA for the specific identification of and delineation among 18 different Cryptosporidium species and genotypes from a wide range of hosts. This mutation scanning approach allowed the rapid and reliable differentiation between species/genotypes differing by as little as 1.3% in the pSSU sequence, with the capacity to detect point mutations. The present findings confirm the usefulness of this tool for the rapid genetic screening of Cryptosporidium samples from any host species, providing a foundation for detailed systematic, epidemiological and ecological studies. Although applied herein to pSSU, this low cost approach should be applicable to a wide range of genetic loci for population genetic investigations of Cryptosporidium.

Detection and genotyping of Cryptosporidium from brown rats (Rattus norvegicus) captured in an urban area of Japan

We investigated the prevalence and genotypes of Cryptosporidium parasite in 50 brown rats (Rattus norvegicus) inhabiting an urban area of Japan. Fecal samples collected from the animals were examined by an immuno-fluorescence assay (IFA). Genomic DNA was extracted directly from fecal sample of each animal and nested PCR was performed to amplify part of the 18S ribosomal RNA (18SrRNA) of the Cryptosporidium species. The detection rate was 8% by IFA and 38% by nested PCR. The sequence and phylogenetic analyses of 13 PCR products showed that the Cryptosporidium from brown rats were clustered into four distinct genotypes. Interestingly, one of the four genotypes was significantly distinct from the C. parvum and C. hominis genotypes. Our results suggest the existence of a new genotype of Cryptosporidium in brown rats.

Detection of Cryptosporidium oocysts in water: effect of the number of samples and analytic replicates on test results

Due to the small number of Cryptosporidium oocysts in water, the number of samples taken and the analyses performed can affect the results of detection. In this study, 42 water samples were collected from one watershed during 20 storm events over 1 year, including duplicate or quadruplicate samples from 16 storm events. Ten samples from four events had three to eight subsamples. They were processed by EPA method 1623, and Cryptosporidium oocysts present were detected by immunofluorescent microscopy or PCR. Altogether, 24 of 39 samples (47 of 67 samples and subsamples) analyzed by microscopy were positive for Cryptosporidium. In contrast, 36 of 42 samples (62 of 76 samples and subsamples) were positive by PCR, including 10 microscopy-negative samples (13 microscopy-negative samples and subsamples). Six of the 24 microscopy-positive samples were negative by PCR, and all samples had one or less oocyst in a 0.5-ml packed pellet volume calculated. Discordant results were obtained by microscopy and PCR from six and three of the storm events, respectively, with multiple samples. Discordant microscopy or PCR results were also obtained among subsamples. Most of the 14 Cryptosporidium genotypes were found over a brief period. Cryptosporidium-positive samples had a mean of 1.9 genotypes per sample, with 39 of the 62 positive samples/subsamples having more than one genotype. Samples/subsamples with more than one genotype had an overall PCR-positive rate of 73%, compared to 34% for those with one genotype. The PCR amplification rate of samples was affected by the volume of DNA used in PCR.

An Irish perspective on Cryptosporidium. Part 1

Cryptosporidiosis, a protozoal disease which causes significant morbidity in humans, is one of the chief causes of diarrhoea in neonatal ruminants. Although the parasite poses a significant threat to public health and animal health in Ireland, its epidemiology on the island is only poorly understood. Environmental studies have shown the waterborne parasite to be widespread in some untreated waterbodies around Ireland. The island's hydrogeological situation, combined with high stocking rates of livestock and the absence of filtration from regular water treatment, render it vulnerable to large-scale outbreaks. This review discusses the parasite in the Irish context and underlines the need for a reference facility to provide active surveillance on the island.

Genotyping of single Cryptosporidium oocysts in sewage by semi-nested PCR and direct sequencing

This study describes an approach for genotyping individual Cryptosporidium oocysts obtained from sewage. We isolated single immunofluorescent assay (IFA)-stained Cryptosporidium oocysts from sewage concentrate using glass capillary pipettes and inverted epifluorescence microscopy. Each isolated Cryptosporidium oocyst was analyzed by semi-nested PCR for the 18S rRNA gene and direct sequencing of the PCR products. A total of 74 of 107 oocysts isolated from sewage were genotyped successfully. Of the 74 genotyped isolates, 51% (38 oocysts) were identified as C. parvum genotype 1, 4% (3 oocysts) of C. parvum VF383 human isolates, 20% (15 oocysts) of C. parvum genotype 2, 14% (10 oocysts) of C. meleagridis, 7% (5 oocysts) of C. sp. Pig 1, 3% (2 oocysts) of C. sp PG1-26 pig isolates and 1% (1 oocyst) of C. parvum CPM1 isolated from mouse. The results of this study demonstrate that 18S rRNA-based semi-nested PCR and direct sequencing can be used to characterize individual Cryptosporidium oocysts and also to reveal the distribution of Cryptosporidium genotypes in environmental waters.

Occurrence of Cryptosporidium spp. oocysts in raw and treated sewage and river water in north-eastern Spain

AIMS

To determine the occurrence and levels of Cryptosporidium parvum oocysts in wastewater and surface waters in north-eastern Spain.

METHODS AND RESULTS

Samples from five sewage treatment plants were taken monthly and quarterly during 2003. In addition, water was collected monthly from the River Llobregat (NE Spain) during the period from 2001 to 2003. All samples were analysed by filtration on cellulose acetate filters or through Envirocheck using EPA method 1623, followed by immunomagnetic separation and examination by laser scanning cytometry. All raw sewage, secondary effluent and river water samples tested were positive for Cryptosporidium oocysts. Of the tertiary sewage effluents tested, 71% were positive for Cryptosporidium oocysts. The proportion of viable oocysts varied according to the sample.

CONCLUSIONS

Two clear maxima were observed during spring and autumn in raw sewage, showing a seasonal distribution and a correlation with the number of cryptosporidiosis cases and rainfall events.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides the first data on the occurrence of Cryptosporidium oocysts in natural waters in north-eastern Spain.

Distribution of cryptosporidium genotypes in storm event water samples from three watersheds in New York

To assess the source and public health significance of Cryptosporidium oocyst contamination in storm runoff, a PCR-restriction fragment length polymorphism technique based on the small-subunit rRNA gene was used in the analysis of 94 storm water samples collected from the Malcolm Brook and N5 stream basins in New York over a 3-year period. The distribution of Cryptosporidium in this study was compared with the data obtained from 27 storm water samples from the Ashokan Brook in a previous study. These three watersheds represented different levels of human activity. Among the total of 121 samples analyzed from the three watersheds, 107 were PCR positive, 101 of which (94.4%) were linked to animal sources. In addition, C. hominis (W14) was detected in six samples collected from the Malcolm Brook over a 2-week period. Altogether, 22 Cryptosporidium species or genotypes were found in storm water samples from these three watersheds, only 11 of which could be attributed to known species/groups of animals. Several Cryptosporidium spp. were commonly found in these three watersheds, including the W1 genotype from an unknown animal source, the W4 genotype from deer, and the W7 genotype from muskrats. Some genotypes were found only in a particular watershed. Aliquots of 113 samples were also analyzed by the Environmental Protection Agency (EPA) Method 1623; 63 samples (55.7%) were positive for Cryptosporidium by microscopy, and 39 (78%) of the 50 microscopy-negative samples were positive by PCR. Results of this study demonstrate that molecular techniques can complement traditional detection methods by providing information on the source of contamination and the human-infective potential of Cryptosporidium oocysts found in water.

Cryptosporidiumparvum oocysts in seawater clams (Chameleagallina) in Italy

Bivalves filter large volumes of water and can concentrate organisms which are pathogenic for humans and animals. Our aim was to evaluate the presence of Cryptosporidium spp. in clams from the Adriatic coast (Abruzzo region) and genetically characterize the oocysts isolated from the clams. From March to July 2003, 960 specimens of clams (Chamelea gallina) present in nature were collected at 500 m from the Tordino, Tronto, Vibrata and Vomano river mouths on the Adriatic sea. The haemolymph and tissues were extracted from the specimens (240 per river mouth) after the specimens had been identified, measured and weighed (live weight). Immunofluorescence tests (IFA) were performed on pools (n = 32) of samples and oocysts of Cryptosporidium spp. were detected in 23 pools of C. gallina. To identify the Cryptosporidium species, all the pools IFA-positive were tested by a PCR assay specific for the Cryptosporidium outer wall protein (COWP) gene. Positive amplicons then were sequenced and analysed. Two pools of clams were positive for Cryptosporidium parvum Genotype 2 (the "bovine" i.e. zoonotic genotype). This is the first time that C. parvum was found in clams from the Adriatic sea in Italy and the case might be of public health importance.

Human cryptosporidiosis: an update with special emphasis on the situation in Europe

The genus Cryptosporidium consists of different species and genotypes which infect a wide range of hosts, including humans. The parasite is ubiquitous and lack of differentiation between the species and strains has made it difficult to track down sources of human and animal infections. Genetic analysis of strains and isolates has led to the redescription of Cryptosporidium with special consideration of the host specificity and possible ways of transmission to humans. Infection with the small oocysts usually occurs directly by faecal-oral transmission, water- or food-borne. In Europe water from different sources is frequently contaminated with oocysts. Generally, humans are most frequently infected with C. hominis in an anthroponotic cycle (especially in cases of infections imported from highly endemic (sub-) tropical regions) and the animal genotype (type II) of C. parvum in a zoonotic cycle which seems to play a major role in autochthonous infections in Switzerland, the UK and probably other European countries. Other species (such as C. felis or the avian species C. meleagridis and C. baileyi) and genotypes are rare in humans and mostly restricted to immunocompromised individuals who are highly susceptible to serious opportunistic cryptosporidial infections.

Cryptosporidium taxonomy: recent advances and implications for public health

There has been an explosion of descriptions of new species of Cryptosporidium during the last two decades. This has been accompanied by confusion regarding the criteria for species designation, largely because of the lack of distinct morphologic differences and strict host specificity among Cryptosporidium spp. A review of the biologic species concept, the International Code of Zoological Nomenclature (ICZN), and current practices for Cryptosporidium species designation calls for the establishment of guidelines for naming Cryptosporidium species. All reports of new Cryptosporidium species should include at least four basic components: oocyst morphology, natural host specificity, genetic characterizations, and compliance with the ICZN. Altogether, 13 Cryptosporidium spp. are currently recognized: C. muris, C. andersoni, C. parvum, C. hominis, C. wrairi, C. felis, and C. cannis in mammals; C. baïleyi, C. meleagridis, and C. galli in birds; C. serpentis and C. saurophilum in reptiles; and C. molnari in fish. With the establishment of a framework for naming Cryptosporidium species and the availability of new taxonomic tools, there should be less confusion associated with the taxonomy of the genus Cryptosporidium. The clarification of Cryptosporidium taxonomy is also useful for understanding the biology of Cryptosporidium spp., assessing the public health significance of Cryptosporidium spp. in animals and the environment, characterizing transmission dynamics, and tracking infection and contamination sources.

Cryptosporidium hominis n. sp. (Apicomplexa: Cryptosporidiidae) from Homo sapiens

The structure and infectivity of the oocysts of a new species of Cryptosporidium from the feces of humans are described. Oocysts are structurally indistinguishable from those of Cryptosporidium parvum. Oocysts of the new species are passed fully sporulated, lack sporocysts. and measure 4.4-5.4 microm (mean = 4.86) x 4.4-5.9 microm (mean = 5.2 microm) with a length to width ratio 1.0-1.09 (mean 1.07) (n = 100). Oocysts were not infectious for ARC Swiss mice, nude mice. Wistar rat pups, puppies, kittens or calves, but were infectious to neonatal gnotobiotic pigs. Pathogenicity studies in the gnotobiotic pig model revealed significant differences in parasite-associated lesion distribution (P = 0.005 to P = 0.02) and intensity of infection (P = 0.04) between C. parvum and this newly described species from humans. In vitro cultivation studies have also revealed growth differences between the two species. Multi-locus analysis of numerous unlinked loci, including a preliminary sequence scan of the entire genome demonstrated this species to be distinct from C. parvum and also demonstrated a lack of recombination, providing further support for its species status. Based on biological and molecular data, this Cryptosporidium infecting the intestine of humans is proposed to be a new species Cryptosporidium hominis n. sp.

Molecular genotyping of human cryptosporidiosis in Northern Ireland: epidemiological aspects and review

BACKGROUND

Cryptosporidium parvum is the most common of the protozoal pathogens associated with gastrointestinal disease in Northern Ireland. Genotyping techniques are valuable in helping to elucidate sources and modes of transmission of this parasite. There have been no reports on the prevalence of genotypes in Northern Ireland, mainly due to a lack of discriminatory genotyping techniques, which recently have become available.

AIM

To investigate the genotype of C. parvum oocysts isolated from human faeces in sporadic cases of cryptosporidiosis in Northern Ireland.

METHODS

Thirty-nine isolates of C. parvum, representing 79.6% of the total 1998 laboratory reports for the Eastern Health and Social Services Board, were investigated. Following DNA extraction from oocysts the thrombospondin-related adhesive protein 2 (TRAP-C2) locus was amplified by polymerase chain reaction (PCR) and subsequently sequenced.

RESULTS

The majority of isolates (87.2%) were classified as bovine genotype II with the remainder (12.8%) being the human genotype I.

CONCLUSIONS

There is a high prevalence of the bovine genotype II parasite in sporadic cases around the greater Belfast area. Epidemiologically, this suggests that the most frequent mode of transmission may be from animals to humans, but does not suggest a high proportion of human to human spread.