Taxonomy and review of the coccidian genus Cryptosporidium (protozoa, apicomplexa)

Multilocus Sequence Typing as a Useful Tool for the Study of the Genetic Diversity and Population Structure of Cryptosporidium Spp

One of the most important aquatic parasites in industrialized countries, Cryptosporidium spp., is a major cause of diarrheal disease in humans and animals worldwide. The contingent evolution of cryptosporidia with hosts, host adaptation, and geographic variation contributed to the creation of species subtypes, thereby shaping their population genetic structures. Multilocus typing tools for population genetic characterizations of transmission dynamics and delineation of mechanisms for the emergence of virulent subtypes have played an important role in improving our understanding of the transmission of this parasite. However, to better understand the significance of different subtypes with clinical disease manifestations and transmission risks, a large number of samples and preferably from different geographical areas need to be analyzed. This review provides an analysis of genetic variation through multilocus sequence typing, provides an overview of subtypes, typing gene markers for Cryptosporidium parvum, Cryptosporidium hominis, Cryptosporidium muris and Cryptosporidium andersoni genotypes and an overview of the hosts of these parasites.

Cryptosporidium: Still Open Scenarios

Cryptosporidiosis is increasingly identified as a leading cause of childhood diarrhea and malnutrition in both low-income and high-income countries. The strong impact on public health in epidemic scenarios makes it increasingly essential to identify the sources of infection and understand the transmission routes in order to apply the right prevention or treatment protocols. The objective of this literature review was to present an overview of the current state of human cryptosporidiosis, reviewing risk factors, discussing advances in the drug treatment and epidemiology, and emphasizing the need to identify a government system for reporting diagnosed cases, hitherto undervalued.

Cryptosporidium Infections in Africa-How Important Is Zoonotic Transmission? A Review of the Evidence

Cryptosporidium, a protozoan parasite in the phylum Apicomplexa, is the etiological agent of cryptosporidiosis, an intestinal infection characterized by profuse watery diarrhea. Over 30 species of Cryptosporidium are recognized, some host specific whereas others infect a broader host range. Cryptosporidium hominis and Cryptosporidium parvum are the species most commonly associated with human infection; C. hominis is largely associated only with human infections, but C. parvum is also associated with infection in animals, especially young ruminants. In some regions, cryptosporidiosis is a serious veterinary problem, particularly for calves, and lambs. Many outbreaks of human cryptosporidiosis have been associated with zoonotic transmission following contact with infected animals. In Africa, where cryptosporidiosis is a major contributor to pediatric morbidity and mortality, evidence suggests transmission is principally anthroponotic. Given the frequent close contact between humans and animals in Africa, the apparent predominance of human-to-human transmission is both interesting and puzzling. In this article, after a brief "text book" introduction to the parasite, we consider in separate sections the different aspects of relevance to Cryptosporidium transmission in African countries, describing different aspects of the various species and subtypes in human and animal infections, considering livestock management practices in different African countries, and looking for any characteristic "hot spots" where zoonotic transmission has apparently occurred. Studies where transmission networks have been investigated are particularly relevant. Finally, in a separate section, we try to gather these different strands of evidence together in order to assess the reasons behind the apparent predominance of anthroponotic transmission in Africa. Reviewing the available evidence provides an opportunity to re-think transmission pathways, not only in Africa but also elsewhere, and also to pose questions. Does the predominance of human-to-human transmission in Africa reflect a relative absence of zoonotic C. parvum in African livestock? Are Africans less susceptible to zoonotic Cryptosporidium infection, perhaps resulting from early immunostimulation by C. hominis or due to inherent genetic traits? Is the African environment-in all its variety-simply more detrimental to oocyst survival? Will the so-called hypertransmissible subtypes, currently relatively rare in Africa, be introduced from Europe or elsewhere, and, if so, will they fade out or establish and spread? Our intention with this manuscript is not only to summarize and consolidate diverse data, thereby providing an overview of data gaps, but also to provide food for thought regarding transmission of a parasite that continues to have a considerable impact on both human and animal health.

The truth about in vitro culture of Cryptosporidium species

Cryptosporidium research has focused on the development of infection control, and effective therapy that has thus far been hampered by the inability to culture Cryptosporidium in vitro. Other limitations include inadequate animal models, cumbersome screening procedures for chemotherapeutic approaches and a lack of tools for genetic manipulation. These limitations can, however, be eased by the improvement and focused development of in vitro cultivation. The ability to culture relevant Cryptosporidium isolates in vitro and to propagate the life cycle stages that are responsible for causing disease in an infected host is still a critical link. This ability will facilitate other relevant approaches, e.g., the ability to knockout genes and the application of broader screening for drug discoveries and vaccine developments, in combination with new discoveries on the parasite's basic biology, genetic manipulation and new life cycle stages. Success in this effort represents an essential step towards significant progress in the control of cryptosporidiosis.

It's official - Cryptosporidium is a gregarine: What are the implications for the water industry?

Parasites of the genus Cryptosporidium are a major cause of diarrhoea and ill-health in humans and animals and are frequent causes of waterborne outbreaks. Until recently, it was thought that Cryptosporidium was an obligate intracellular parasite that only replicated within a suitable host, and that faecally shed oocysts could survive in the environment but could not multiply. In light of extensive biological and molecular data, including the ability of Cryptosporidium to complete its life cycle in the absence of a host and the production of novel extracellular stages, Cryptosporidium has been formally transferred from the Coccidia, to a new subclass, Cryptogregaria, with gregarine parasites. In this review, we discuss the close relationship between Cryptosporidium and gregarines and discuss the implications for the water industry.

Expression of Cryptosporidium parvum Cpa135/CpCCP1 chimeras in Giardia duodenalis: organization of the protein domains affects the protein secretion pathway

Cpa135 is a multidomain antigenic protein secreted at the sporozoite stage of the Apicomplexa protozoan Cryptosporidium parvum. Previous studies have shown that the protozoan flagellate parasite Giardia duodenalis is a suitable system for the heterologous expression of secreted proteins of Apicomplexa. Here, we designed three different Cpa135 variants fused to a C-terminal HA tag in order to test their expression in G. duodenalis under the control of the inducible promoter of the cyst wall protein 1 gene (cwp1). The three Cpa135 chimeras encompassed different portions of the protein; CpaG encodes the entire polypeptide of 1574 amino acids (aa); CpaGΔC includes the first 826 aa at the N-terminus; and CpaGΔN consists in of the final 833 aa at the C-terminus. Immunoblot experiments showed that CpaG and CpaGΔN maintained the epitopes recognized by anti-C. parvum-specific human serum. The intracellular localization and transport of the three Cpa135 variants were studied by immunofluorescence in combination with G. duodenalis-specific antibodies. CpaGΔC was mainly accumulated in the endoplasmic reticulum and the intact form was also excreted in the medium. Differently, the Cpa135 chimeras possessing an intact C-terminus (CpaG and CpaGΔN) were transported towards the forming cyst wall possibly and were not detected in the medium. Furthermore, the full-length CpaG was incorporated into the cyst wall. The data presented suggest that the C-terminus of Cpa135, which includes a cysteine reach domain, could influence the secretion of the chimeric proteins.

Gastric cryptosporidiosis in freshwater angelfish (Pterophyllum scalare)

A freshwater angelfish (Pterophyllum scalare) hatchery experienced variable levels of emaciation, poor growth rates, swollen coelomic cavities, anorexia, listlessness, and increased mortality within their fish. Multiple chemotherapeutic trials had been attempted without success. In affected fish, large numbers of protozoa were identified both histologically and ultrastructurally associated with the gastric mucosa. The youngest cohort of parasitized fish was the most severely affected and demonstrated the greatest morbidity and mortality. The protozoa were morphologically most consistent with Cryptosporidium. All of the protozoan life stages were identified ultrastructurally and protozoal genomic DNA was isolated from parasitized tissue viscera and sequenced. Histological, ultrastructural, genetic, and phylogenetic analyses confirmed this protozoal organism to be a novel species of Cryptosporidium.

Species tree inference by minimizing deep coalescences

In a 1997 seminal paper, W. Maddison proposed minimizing deep coalescences, or MDC, as an optimization criterion for inferring the species tree from a set of incongruent gene trees, assuming the incongruence is exclusively due to lineage sorting. In a subsequent paper, Maddison and Knowles provided and implemented a search heuristic for optimizing the MDC criterion, given a set of gene trees. However, the heuristic is not guaranteed to compute optimal solutions, and its hill-climbing search makes it slow in practice. In this paper, we provide two exact solutions to the problem of inferring the species tree from a set of gene trees under the MDC criterion. In other words, our solutions are guaranteed to find the tree that minimizes the total number of deep coalescences from a set of gene trees. One solution is based on a novel integer linear programming (ILP) formulation, and another is based on a simple dynamic programming (DP) approach. Powerful ILP solvers, such as CPLEX, make the first solution appealing, particularly for very large-scale instances of the problem, whereas the DP-based solution eliminates dependence on proprietary tools, and its simplicity makes it easy to integrate with other genomic events that may cause gene tree incongruence. Using the exact solutions, we analyze a data set of 106 loci from eight yeast species, a data set of 268 loci from eight Apicomplexan species, and several simulated data sets. We show that the MDC criterion provides very accurate estimates of the species tree topologies, and that our solutions are very fast, thus allowing for the accurate analysis of genome-scale data sets. Further, the efficiency of the solutions allow for quick exploration of sub-optimal solutions, which is important for a parsimony-based criterion such as MDC, as we show. We show that searching for the species tree in the compatibility graph of the clusters induced by the gene trees may be sufficient in practice, a finding that helps ameliorate the computational requirements of optimization solutions. Further, we study the statistical consistency and convergence rate of the MDC criterion, as well as its optimality in inferring the species tree. Finally, we show how our solutions can be used to identify potential horizontal gene transfer events that may have caused some of the incongruence in the data, thus augmenting Maddison's original framework. We have implemented our solutions in the PhyloNet software package, which is freely available at: http://bioinfo.cs.rice.edu/phylonet.

Inferring the evolutionary history of a set of species, known as the species tree, is a task of utmost significance in biology and beyond. The traditional approach to accomplishing this task from molecular sequences entails sequencing a gene in the set of species under consideration, reconstructing the gene's evolutionary history, and declaring it to be the species tree. However, recent analyses of multiple gene data sets, made available thanks to advances in sequencing technologies, have indicated that gene trees in the same group of species may disagree with each other, as well as with the species tree. Therefore, the development of methods for inferring the species tree despite such disagreements is imperative.

In this paper, we propose such a method, which seeks the tree that minimizes the amount of disagreement between the input set of gene trees and the inferred one. We have implemented our method and studied its performance, in terms of accuracy and computational efficiency, on two biological data sets and a large number of simulated data sets. Our analyses, of both the biological and synthetic data sets, indicate high accuracy of the method, as well as computationally efficient solutions in practice. Hence, our method makes a good candidate for inferring accurate species trees, despite gene tree disagreements, at a genomic scale.

Genetic variability in parasites and host—parasite interactions

We have examined genetic variability in parasites in the context of ecological interactions with the host. Recent research onEchinococcus, GiardiaandCryptosporidiumhas been used to illustrate: (i) the problems that parasite variability and species recognition pose for understanding the complex and often controversial relationship between parasite and host occurrence; (ii) the need for accurate parasite characterization and the application of appropriate molecular techniques to studies on parasite transmission if fundamental questions about zoonotic relationships and risk factors are to be answered; (iii) our lack of understanding about within-host interactions between genetically heterogeneous parasites at the inter-and intraspecific levels, and the significance of such interactions with respect to evolutionary considerations and the clinical outcome of parasite infections. If advances in molecular biology and mathematical ecology are to be realized, we need to give serious consideration to the development of appropriate species concepts and in vivo systems for testing the predictions and assumptions of theoretical models.

Cryptosporidium in birds, fish and amphibians

Whilst considerable information is available for avian cryptosporidiosis, scant information is available for Cryptosporidium infections in fish and amphibians. The present review details recent studies in avian cryptosporidiosis and our current knowledge of piscine and amphibian infections.

The Apicomplexan whole-genome phylogeny: an analysis of incongruence among gene trees

The protistan phylum Apicomplexa contains many important pathogens and is the subject of intense genome sequencing efforts. Based upon the genome sequences from seven apicomplexan species and a ciliate outgroup, we identified 268 single-copy genes suitable for phylogenetic inference. Both concatenation and consensus approaches inferred the same species tree topology. This topology is consistent with most prior conceptions of apicomplexan evolution based upon ultrastructural and developmental characters, that is, the piroplasm genera Theileria and Babesia form the sister group to the Plasmodium species, the coccidian genera Eimeria and Toxoplasma are monophyletic and are the sister group to the Plasmodium species and piroplasm genera, and Cryptosporidium forms the sister group to the above mentioned with the ciliate Tetrahymena as the outgroup. The level of incongruence among gene trees appears to be high at first glance; only 19% of the genes support the species tree, and a total of 48 different gene-tree topologies are observed. Detailed investigations suggest that the low signal-to-noise ratio in many genes may be the main source of incongruence. The probability of being consistent with the species tree increases as a function of the minimum bootstrap support observed at tree nodes for a given gene tree. Moreover, gene sequences that generate high bootstrap support are robust to the changes in alignment parameters or phylogenetic method used. However, caution should be taken in that some genes can infer a "wrong" tree with strong support because of paralogy, model violations, or other causes. The importance of examining multiple, unlinked genes that possess a strong phylogenetic signal cannot be overstated.

Cryptosporidiosis in birds--a review

The taxonomy, morphology and life cycle, host species, incidence, pathology, transmission, immunity, diagnosis and control of cryptosporidiosis in birds are reviewed.

Development of a Cryptosporidium oocyst assay using an automated fiber optic-based biosensor

An intestinal protozoan parasite, Cryptosporidium parvum, is a major cause of waterborne gastrointestinal disease worldwide. Detection of Cryptosporidium oocysts in potable water is a high priority for the water treatment industry to reduce potential outbreaks among the consumer populace. Anti-Cryptosporidium oocyst polyclonal and monoclonal antibodies were tested as capture and detection reagents for use in a fiber optic biosensor assay for the detection of Cryptosporidium oocysts. Antibodies were validated using enzyme-linked immunosorbent assays, flow cytometry, Western blotting and fluorescent microscopy. Oocysts could be detected at a concentration of 105 oocysts/ml when the polyclonal antibodies were used as the capture and detection reagents. When oocysts were boiled prior to detection, a ten-fold increase in sensitivity was achieved using the polyclonal antibody. Western blotting and immunofluorescence revealed that both the monoclonal and polyclonal antibodies recognize a large (>300 kDa) molecular weight mucin-like antigen present on the surface of the oocyst wall. The polyclonal antibody also reacted with a small (105 kDa) molecular weight antigen that was present in boiled samples of oocysts. Preliminary steps to design an in-line biosensor assay system have shown that oocysts would have to be concentrated from water samples and heat treated to allow detection by a biosensor assay.

Possible involvement of Artemia as live diet in the transmission of cryptosporidiosis in cultured fish

The viability of Cryptosporidium parvum oocysts ingested by Artemia franciscana metanauplii was evaluated using two fluorogenic vital dyes. There was no significant difference (p = 0.09) between the viability of oocysts maintained in saline (control) and those recovered from the digestive tract of the microcrustacean 24 h after ingestion (95 vs 90% viable oocysts). The results suggest that Artemia, used as a life food in fish larviculture, may act as a vehicle for transmission of piscine cryptosporidiosis caused by Cryptosporidium molnari and Cryptosporidium scophthalmi.

Criptosporidiose: uma revisão sobre a sua implicação na conservação dos mamíferos aquáticos

A criptosporidiose é uma doença parasitária emergente que vem sendo relatada em diversas espécies de mamíferos, incluindo os aquáticos. Esta revisão trata da epidemiologia da infecção por Cryptosporidium spp. em mamíferos aquáticos. A idade dos animais, dose infectante e o estado imunológico podem influenciar na apresentação clínica, e quando associados a outros patógenos pode levar o animal a óbito. A contaminação dos recursos hídricos constitui um dos principais meios de disseminação do parasito, que foi identificado por diferentes técnicas de análise. A adequação das estruturas de saneamento, utilização de métodos apropriados para a inativação dos oocistos e garantia das normas de higiene pessoal constituem algumas das maneiras recomendadas para minimizar a disseminação do Cryptosporidium entre os mamíferos aquáticos.

[Prevalence of Cryptosporidium sp. in institutionalized dogs in the city of São Paulo, Brazil]

OBJECTIVE

Dogs play an important role as infection source of human cryptosporidiosis. The objective of the study was to determine the prevalence of Cryptosporidium sp. in dogs as well as to compare two techniques of fecal analysis.

METHODS

Four-hundred and fifty canine fecal samples from the city of São Paulo were analyzed between 2003 and 2004. Fecal samples were randomly selected from dogs housed in a university veterinary hospital (group 1, n=200) and private kennels (group 2, n=250). The detection of Cryptosporidium was performed using modified Ziehl-Neelsen staining and Polymerase Chain Reaction (PCR) technique. Statistical analysis was performed using the two-tailed test of significance at 5% confidence interval (z critical=+/-1.645).

RESULTS

Only Cryptosporidium parvum oocysts were found. The prevalences found by light microscopy examination and PCR techniques were 8.8% and 9.5%, respectively. Young animals showed a lower frequency (5.5%) compared to adults (10.1%). There was no statistically significant difference in Cryptosporidium prevalence between males and females.

CONCLUSIONS

The prevalence of C. parvum in the canine population studied was similar to that one found in the literature and affects equally males and females. The use of PCR allowed the detection of more positive cases than light microscopy.

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.

Molecular and biological characterization of a Cryptosporidium molnari-like isolate from a guppy (Poecilia reticulata)

Histological, morphological, genetic, and phylogenetic analyses of a Cryptosporidium molnari-like isolate from a guppy (Poecilia reticulata) identified stages consistent with those of C. molnari and revealed that C. molnari is genetically very distinct from all other species of Cryptosporidium. This study represents the first genetic characterization of C. molnari.

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 spp. no ambiente aquático: aspectos relevantes da disseminação e diagnóstico

A criptosporidiose é uma doença de importância para a saúde pública. A via de transmissão do Cryptosporidium parvum é associada freqüentemente à contaminação de água. Porém, estudos epidemiológicos revelam que sua incidência no ambiente aquático é subestimada. A falta de método apropriado de detecção para a pesquisa dos oocistos em amostras de água contribui para isso. O artigo discute vários aspectos do tema, dentre eles, a ocorrência desse patógeno no ambiente aquático e os avanços nos métodos de detecção. Apesar da existência de técnicas de biologia molecular para a identificação do agente, métodos parasitológicos ainda apresentam resultados satisfatórios. A reação em cadeia de polimerase (PCR) é um método de detecção promissor. A identificação dos oocistos de Cryptosporidium spp. na amostra de água é influenciada pelo número de oocistos presentes, pela sensibilidade do método e pelo método de concentração dos oocistos na amostra, cujo aperfeiçoamento é fundamental para a precisão da análise e pesquisa do parasito.

Cryptosporidium molnari n. sp. (Apicomplexa: Cryptosporidiidae) infecting two marine fish species, Sparus aurata L. and Dicentrarchus labrax L

Cryptosporidium molnari n. sp. is described from two teleost fish, the gilthead sea bream (Sparus aurata L.) and the European sea bass (Dicentrarchus labrax L.). The parasite was found mainly in the stomach epithelium and seldom in the intestine. Oocysts were almost spherical, with four naked sporozoites and a prominent residuum, and measured 3.23-5.45 x 3.02-5.04 (mean 4.72 x 4.47) microm in the type host, gilthead sea bream (shape index 1-1.17, mean 1.05). Sporulation was endogenous, as fully sporulated oocysts were found within the fish, both in the stomach epithelium and lumen, and in faeces. Oocysts and other stages of C. molnari fit most of the diagnostic features of the genus Cryptosporidium, but differ from hitherto described species, including piscine ones. All stages were located within a host contributed parasitophorous vacuole lined by a double host microvillar membrane. Merogonial and gamogonial stages appeared in the typical extracytoplasmic position, whereas oogonial and sporogonial stages were located deeply within the epithelium. Ultrastructural features, including the characteristic contact zone of the parasite with the host epithelial surface, were mostly coincident with those of other Cryptosporidium spp. Mitochondria were found in dividing meronts, merozoites, microgamonts and sporozoites. Pathological effects were more evident in gilthead sea bream, which also exhibited a clearly higher prevalence (24.4 versus 4.64% in sea bass). External clinical signs, consisting of whitish faeces, abdominal swelling and ascites, were rarely observed, in contrast with important histopathological damage. The wide zones of epithelium invaded by oogonial and sporogonial stages appeared necrotic, with abundant cell debris, and sloughing of epithelial cells, which detached to the lumen. No inflammation reaction was observed and the cellular reaction was limited to the cells involved in the engulfing of intraepithelial stages and debris, probably macrophages.

Molecular phylogeny and evolutionary relationships of Cryptosporidium parasites at the actin locus

To further validate previous observations in the taxonomy of Cryptosporidium parasites, the phylogenetic relationship was analyzed among various Cryptosporidium parasites at the actin locus. Nucleotide sequences of the actin gene were obtained from 9 putative Cryptosporidium species (C. parvum, C. andersoni, C. baileyi, C. felis, C. meleagridis, C. muris, C. saurophilum, C. serpentis, and C. wrairi) and various C. parvum genotypes. After multiple alignment of the obtained actin sequences, genetic distances were measured, and phylogenetic trees were constructed. Results of the analysis confirmed the presence of genetically distinct species within Cryptosporidium and various distinct genotypes within C. parvum. The phylogenetic tree constructed on the basis of the actin sequences was largely in agreement with previous results based on small subunit rRNA, 70-kDa heat shock protein, and Cryptosporidium oocyst wall protein genes. The Cryptosporidium species formed 2 major clades; isolates of C. andersoni, C. muris, and C. serpentis formed the first major group, whereas isolates of all other species, as well as various C. parvum genotypes, formed the second major group. Intragenotype variations were low or absent at this locus.

Cryptosporidium muris infection in an HIV-infected adult, Kenya

We describe a case of Cryptosporidium muris infection in an HIV-infected adult with diarrhea in Kenya. Sequence analysis of an 840-bp region of the 18S rRNA gene locus demonstrated the isolate had 100% nucleotide identity with C. muris recovered from a rock hyrax, 98.8% with a C. muris "calf" isolate, 95.5% with C. serpentis, but only 87.8% with C. parvum "human" type.

Contribution to the laboratory diagnosis of human cryptosporidiosis

Human cryptosporidiosis is an infection caused by Cryptosporidium spp, a coccidial protozoan of emergencial pathogenicity and responsible for severe and prostrating watery diarrhea, mainly in immunocompromised patients. Smears of stools submitted to concentration and staining by carbol fuchsin technique has been used in our laboratory as a diagnostic procedure for cryptosporidiosis. The long time observing the smears in the microscope due to the small size of the forms and the low contrast of the staining led us to introduce some modifications in the original protocol for the acid-fast staining. The smears were treated with the carbol fuchsin solution for 3 minutes as recommended by LENNETTE et al., 1985 and the solution of the ethyl alcohol 70%-chloride acid 0.5% was used instead of the ethyl alcohol-sulfuric acid 5% recommended by HENRIKSEN & POHLENZ, 1981. Smears were treated with the discoloration solution for 2 minutes. These modifications promoted a better washing out of the excess of carbol fuchsin therefore increasing the dye efficiency. In such conditions, the visualization of protozoan oocysts on the slides examined became easier. They were observed by the contrast of their intense pink-reddish pigmentation against the blue background. It's worthwhile to emphasize that these modifications offer advantages when time and accuracy are concerned.

Variation in Cryptosporidium: towards a taxonomic revision of the genus

Cryptosporidium is an important cause of enteric disease in humans and other animals. Limitations associated with conventional diagnostic methods for cryptosporidiosis based on morphological features, coupled with the difficulty of characterising parasites isolated in the laboratory, have restricted our ability to clearly identify species. The application of sensitive molecular approaches has obviated the necessity for laboratory amplification. Such studies have found considerable evidence of genetic heterogeneity among isolates of Cryptosporidium from different species of vertebrate, and there is now mounting evidence suggesting that a series of host-adapted genotypes/strains/species of the parasite exist. In this article, studies on the molecular characterisation of Cryptosporidium during the last 5 years are reviewed and put into perspective with the past and present taxonomy of the genus. The predictive value of achieving a sound taxonomy for the genus Cryptosporidium with respect to understanding its epidemiology and transmission and controlling outbreaks of the disease is also discussed.

Phylogenetic analysis of Cryptosporidium parasites based on the small-subunit rRNA gene locus

Biological data support the hypothesis that there are multiple species in the genus Cryptosporidium, but a recent analysis of the available genetic data suggested that there is insufficient evidence for species differentiation. In order to resolve the controversy in the taxonomy of this parasite genus, we characterized the small-subunit rRNA genes of Cryptosporidium parvum, Cryptosporidium baileyi, Cryptosporidium muris, and Cryptosporidium serpentis and performed a phylogenetic analysis of the genus Cryptosporidium. Our study revealed that the genus Cryptosporidium contains the phylogenetically distinct species C. parvum, C. muris, C. baileyi, and C. serpentis, which is consistent with the biological characteristics and host specificity data. The Cryptosporidium species formed two clades, with C. parvum and C. baileyi belonging to one clade and C. muris and C. serpentis belonging to the other clade. Within C. parvum, human genotype isolates and guinea pig isolates (known as Cryptosporidium wrairi) each differed from bovine genotype isolates by the nucleotide sequence in four regions. A C. muris isolate from cattle was also different from parasites isolated from a rock hyrax and a Bactrian camel. Minor differences were also detected between C. serpentis isolates from snakes and lizards. Based on the genetic information, a species- and strain-specific PCR-restriction fragment length polymorphism diagnostic tool was developed.

Distribution of actin and tropomyosin in Cryptosporidium muris

Actin and tropomyosin of Cryptosporidium muris were localized by immunogold labeling. Two kinds of antibodies for actin labeling were used. The polyclonal antibody to skeletal muscle (chicken back muscle) actin was labeled on the pellicle and cytoplasmic vacuoles of parasites. The feeder organelle has showed a small amount of polyclonal actin antibody labeling as well. Whereas the monoclonal antibody to smooth muscle (chicken gizzard muscle) actin was chiefly labeled on the filamentous cytoplasm of parasites. The apical portion of host gastric epithelial cell cytoplasm was also labeled by smooth muscle actin together. The polyclonal antibody to tropomyosin was much more labeled at C. muris than host cells, so it could be easily identified even with low magnification (x2,000). The tropomyosin was observed along the pellicle, cytoplasmic vacuoles, and around the nucleus also. The skeletal muscle type actin seems to play a role in various cellular functions with tropomyosin in C. muris; on the other hand, the smooth muscle type actin was located mainly on the filamentous cytoplasm and supported the parasites' firm attachment to host cells. Tropomyosin on the pellicle was thought to be able to stimulate the host as a major antigen through continuous shedding out by the escape of sporozoites or merozoites from their mother cells.

Species and strain-specific typing of Cryptosporidium parasites in clinical and environmental samples

Cryptosporidiosis has recently attracted attention as an emerging waterborne and foodborne disease as well as an opportunistic infection in HIV infected individuals. The lack of genetic information, however, has resulted in confusion in the taxonomy of Cryptosporidium parasites and in the development of molecular tools for the identification and typing of oocysts in environmental samples. Phylogenetic analysis of the small subunit ribosomal RNA (SSU rRNA) gene has shown that the genus Cryptosporidium comprises several distinct species. Our data show the presence of at least four species: C. parvum, C. muris, C. baileyi and C. serpentis (C. meleagridis, C. nasorum and C. felis were not studied). Within each species, there is some sequence variation. Thus, various genotypes (genotype 1, genotype 2, guinea pig genotype, monkey genotype and koala genotype, etc.) of C. parvum differ from each other in six regions of the SSU rRNA gene. Information on polymorphism in Cryptosporidium parasites has been used in the development of species and strain-specific diagnostic tools. Use of these tools in the characterization of oocysts in various samples indicates that C. parvum genotype 1 is the strain responsible for most human Cryptosporidium infections. In contrast, genotype 2 is probably one of the major sources for environmental contamination, and has been found in most oysters examined from Chesapeake Bay that may serve as biologic monitors of estuarine waters.

Cryptosporidiosis in Houston, Texas. A report of 95 cases

Cryptosporidiosis is an important cause of diarrhea. We identified 95 patients with cryptosporidiosis over a 6-year period in our county hospital system, including 9 children and 86 adults infected with the human immunodeficiency virus (HIV). Risk factors included male-to-male sexual practices and Hispanic race. Diarrhea, weight loss, and gastrointestinal complaints were the most common symptoms at presentation. Among the HIV-infected adults, 20 (23%) developed biliary tract disease. Biliary involvement was associated with low CD4 counts. Treatment with paromomycin and antimotility agents was effective in reducing diarrheal symptoms in 54 of 70 (77%) patients with the acquired immunodeficiency syndrome (AIDS), although there was a high rate of relapse. Paromomycin did not prevent the development of biliary disease. Biliary disease responded to cholecystectomy or sphincterotomy with stent placement. Though often a cause of morbidity, cryptosporidiosis was only rarely the cause of death, even among patients with HIV. Cryptosporidiosis continues to be an important medical problem even in developed-countries. Current methods of prevention and treatment are suboptimal.

A survey for Cryptosporidium spp. in mammals at the Barcelona Zoo

Mammals housed at the Barcelona Zoo belonging to the orders Carnivora, Artiodactyla, Perissodactyla and Proboscidea were examined for Cryptosporidium infections. A total of 183 fecal samples from 17 carnivores and 34 herbivores revealed patent infections in only 6 herbivore species (5 artiodactyls of the families Bovidae and Giraffidae and 1 perissodactyl of the family Rhinocerotidae); all carnivores were negative. Intensity of infection was found to be generally low. Connochaetes taurinus taurinus, Gazella dorcas neglecta, Kobus ellipsiprymmus and Giraffa camelopardalis constitute new host species for the parasite.

Prevalence, detection and control of Cryptosporidium parvum in food

The role of Cryptosporidium parvum as a foodborne pathogen has not been well documented. Epidemiological features of this parasitic protozoon lead to the assumption that the incidence of cryptosporidiosis due to contaminated food is under-estimated. The high prevalence of C. parvum among dairy herds has increased the spread of oocysts in the farm environment, and their potential presence in raw milk and other raw foods. In October 1993, the first well-documented foodborne outbreak was reported in Maine, USA, and was caused by contaminated hand-pressed apple cider. Although various cases of cryptosporidiosis among humans have pointed to raw milk and other raw foods as possible sources of infection, a conclusive demonstration of foodborne cryptosporidiosis has rarely been established. The limited numbers of oocysts in the suspected samples and the lack of sensitive detection methods adapted for oocyst detection in food contribute to this under-reporting. This review paper discusses various aspects of Cryptosporidium spp. and cryptosporidiosis, including the routes of transmission, the control of oocysts in food, and the available detection methods. The polymerase chain reaction (PCR) combined with DNA probe hybridization is a promising detection method. Recent knowledge on the molecular biology of the parasite for the development of new PCR assays and their potential use in the detection of C. parvum in food are described.

Codon usage in Cryptosporidium parvum differs from that in other Eimeriorina

Codon usage of Crytosporidium parvum was compared with those of other Eimeriorina Toxoplasma gondii and Eimeria tenella and revealed a biased use of synonymous codons with a preference for NNU (40.0%) and NNA (33.4%). There was no close resemblance of the codon usage of C. parvum to T. gondii (correlation coefficient, r = 0.14) or E. tenella (r = 0.14) but it was similar to Entamoeba histolytica (r = 0.75) and Plasmodium falciparum (r = 0.5). Analysis of the codon usage in homologous gene sequences (actin, beta-tubulin) also failed to reveal a close relationship between C. parvum and T. gondii or E. tenella. The low usage codons in C. parvum were most frequently used codons in T. gondii and E. tenella. These observations are consistent with 18S rRNA sequence analysis which shows no close relationship of Cryptosporidium with other Eimeriorina (Sarcocystis, Toxoplasma and Eimeria) and questions the validity of the current classification of C. parvum.

Infectivity of a Cryptosporidium species isolated from a domestic cat (Felis domestica) in lambs and mice

Two neonatal lambs were inoculated orally with purified Cryptosporidium species oocysts isolated from a farm cat. Oocysts first appeared in the faeces of the two lambs three and 10 days after infection. Two distinct sizes of oocysts were observed in the faeces of both the cat and the lambs, the smaller measuring approximately 5.0 x 4.5 microns and the larger measuring approximately 6.0 x 5.0 microns in diameter. The smaller type predominated. Histological examination of the alimentary tract of the lambs revealed endogenous stages of Cryptosporidium in the epithelial borders of the ileum. In addition, Cryptosporidium oocysts were detected in impression smears from the jejunum, ileum, caecum and colon. Suspensions of 10(3) oocysts from the faeces of the farm cat were inoculated into each of 10 newborn mice and 10(4) oocysts from the two experimentally infected lambs were inoculated into each of 20 newborn mice. Cryptosporidium oocysts were detected in gut homogenates from 19 of the 20 mice inoculated with oocysts from the lambs but in none of the mice inoculated with oocysts from the cat.

Cryptosporidiosis of liver and pancreas in rhesus monkeys with experimental SIV infection

Following an experimental SIV infection, 11 rhesus monkeys were evaluated to determine the presence of opportunistic infections. Five animals had severe alterations of the hepatobiliary tree, three of which were associated with the presence of numerous Cryptosporidium spp. Subacute to chronic inflammatory changes were observed in the pancreatic ducts of four animals, one without histologic evidence of parasites. In one animal, the inflamed ducts were associated with a chronic interstitial pancreatitis. The rate of Cryptosporidium infection together with hepatic and pancreatic involvement (36%) supports the hypothesis that systemic cryptosporidiosis is the result of a loss of protective mucosal immunity.

Chronic cryptosporidiosis in Australian elapid snakes: control of an outbreak in a captive colony

An outbreak of chronic cryptosporidiosis resulting in hypertrophic gastritis occurred in a captive colony of Australian elapid snakes. Two species of the genus Notechis were involved: Notechis ater (Black Tiger Snake) and Notechis scutatus (Eastern or Mainland Tiger Snake). The infection was eventually fatal in all 9 affected snakes. Typical histopathological findings of the stomach included mucosal thickening with cystic dilatation of gastric glands, moderate oedema and fibrosis of the lamina propria, and a mild to moderate patchy infiltration of inflammatory cells. Procedures implemented to contain the outbreak included the use of a formaldehyde-based disinfectant, prompt removal of faecal matter, uneaten and regurgitated food from enclosures, and examination of faecal specimens for Cryptosporidium oocytes and other pathogens.

Isoenzyme variation within the genus Cryptosporidium

Soluble extracts of the oocysts of Cryptosporidium parvum had demonstrable, but low, activities of malate dehydrogenase (MDH, EC. 1.1.1.37), carboxylesterase (ES, EC 3.1.1.1) and lactate dehydrogenase (LDH, EC. 1.1.1.27) following thin-layer starch-gel electrophoresis. Much higher activities of glucose phosphate isomerase (GPI, EC. 5.3.1.9) and phosphoglucomutase (PGM, EC. 2.7.5.1) were found, and zymograms of these two enzymes were used to characterise isolates of C. parvum from human, bovine, ovine and cervine sources, C. muris from the brown rat and C. baileyi from young turkeys. PGM and GPI zymograms clearly distinguished between C. parvum, C. muris and C. baileyi. The five isolates of C. parvum showed the same electrophoretic mobility for GPI, whereas the PGM mobility of the single human isolate of C. parvum examined was clearly different from that of the other isolates. This is the first report of the use of isoenzymes to distinguish between species and isolates of Cryptosporidium.

Freeze-fracture study of the site of attachment of Cryptosporidium muris in gastric glands

The mode and organization of the attachment site of Cryptosporidium muris to gastric glands of stomach were investigated by the freeze-fracture method. Cryptosporidium muris was enveloped by a double membrane, of host plasma membrane origin, which formed the parasitophorous vacuole. The outer membrane of the double membrane was continuous with host plasma membrane, while the inner membrane was connected with the anterior part of the parasite plasma membrane at the annular ring. The density of intramembranous particles (IMP) was severely altered at the above two junctures. The parasitophorous outer membrane showed low IMP-density when compared to the host plasma membrane, although both membranes were continuous at the dense band. The inner membrane had few IMP, whereas the parasite plasma membrane showed numerous IMP, although both membranes were continuous at the annular ring. The size of dense band and annular ring was similar in diameter. The feeder organelle was clearly visible as membrane folds in freeze-fracture and some of them were connected with small vesicles of cytoplasm, indicating that the feeder organelle may play an important role for incorporation of nutrients from the host cell.

Cryptosporidiosis

Before 1982, only eight case reports of human cryptosporidiosis and fewer than 30 papers on Cryptosporidium spp. appeared in the biomedical literature. At that time, cryptosporidiosis was thought to be an infrequent infection in animals and rarely an opportunistic infection in humans. The concept of Cryptosporidium spp. as pathogens has changed dramatically within the past 8 years because of improved diagnostic techniques, increased awareness within the biomedical community, and the development of basic research programs in numerous laboratories. Presently, greater than 1,000 publications including over 400 case reports in the biomedical literature address Cryptosporidium spp. and cryptosporidiosis. Cryptosporidium parvum is now thought to be one of the three most common enteropathogens causing diarrheal illness in humans worldwide, especially in developing countries. It is likely that cryptosporidiosis was previously included in the 25 to 35% of diarrheal illness with unknown etiology. Because of the severity and length of diarrheal illness and because no effective therapy has been identified, cryptosporidiosis is one of the most ominous infections associated with AIDS. The role of C. parvum as an enteropathogen is well established; documentation of its role as a cause of hepatobiliary and respiratory diseases is now appearing in the literature. Our present understanding of the natural history, epidemiology, biology, and immunology of Cryptosporidium spp. as well as the clinical features, pathogenicity, and treatment of cryptosporidiosis are reviewed here.

[Isolation and identification of Cryptosporidium from various animals in Korea. II. Identification of Cryptosporidium muris from mice]

Each of SPF mice(Scl: ICR strain, 3-week-old males) was inoculated with 5 x 10(4) oocysts of Cryptosporidium by stomach tube. The oocysts were large type one which was previously isolated from Korean mice, and passaged in 3-week-old SPF mice. The patterns of oocyst discharge were monitored daily, and in order to observe the ultrastructure of developmental stages the stomach of the mice was examined by transmission electron microscopy (TEM) at 4 weeks post-inoculation. The prepatent period for 6 mice was 5.6 days post-inoculation on the average, and the patent period was 63.2 days. The number of oocysts discharged per day from the mice reached peak on day 36.6 post-inoculation on the average. A large number of oocysts were found in fecal samples obtained from inoculated mice on days 30-50 post-inoculation. C. muris was larger than C. parvum at almost every developmental stages, the size difference being 1.4 times in oocysts, 2.4 times in sporozoites, 1.6 times in merozoites, and 1.5 times in microgametes. The ultrastructural features of the attachment site of C. muris to the mucus cells were remarkably different from those of C. parvum and its closely related species. The anterior projection of the protozoa (C. muris), the outer aspect of which was surrounded by a thick filamentous process of the host cell, has not been reported at any developmental stages of C. parvum or its closely related species. The size of the oocysts of strain RN 66 was larger than that of Korean mice origin. The above results reveal that the large type Cryptosporidium of Korean mice origin is identified as Cryptosporidium muris and this type was named as C. muris (strain MCR).

The first finding of Cryptosporidium baileyi in man

Oocysts of cryptosporidia whose morphology and measurements corresponded with those of the species Cryptosporidium baileyi were found in the stool of an immunodeficient patient. In autopsy material, cryptosporidia were found in the esophagus, whole intestine, trachea, larynx, lungs, and gall and urinary bladders. None of the 69 suckling mice inoculated with this isolate developed cryptosporidial infection. Infection was successful in 26 chickens inoculated perorally and 6 others subjected to intratracheal inoculation; it was localized in the duodenum, jejunum, bursa Fabricii, and respiratory tract. From day 12 after infection, oocysts of cryptosporidia were found in the excrement. Human infection with C. baileyi may have occurred due to disruption of the immune system by human immunodeficiency virus (HIV) and to immunosuppressive therapy undertaken after allogeneic kidney transplantation.

Some infectious causes of diarrhea in young farm animals

Escherichia coli, rotaviruses, and Cryptosporidium parvum are discussed in this review as they relate to enteric disease in calves, lambs, and pigs. These microorganisms are frequently incriminated as causative agents in diarrheas among neonatal food animals, and in some cases different strains or serotypes of the same organism cause diarrhea in humans. E. coli causes diarrhea by mechanisms that include production of heat-labile or heat-stable enterotoxins and synthesis of potent cytotoxins, and some strains cause diarrhea by yet undetermined mechanisms. Rotaviruses and C. parvum induce various degrees of villous atrophy. Rotaviruses infect and replicate within the cytoplasm of enterocytes, whereas C. parvum resides in an intracellular, extracytoplasmic location. E. coli, rotavirus, and C. parvum infections are of concern to producers, veterinarians, and public health officials. These agents are a major cause of economic loss to the producer because of costs associated with therapy, reduced performance, and high morbidity and mortality rates. Moreover, diarrheic animals may harbor, incubate, and act as a source to healthy animals and humans of some of these agents.