Cryptosporidium spp. and cryptosporidiosis.

Epidemiology of Cryptosporidium: transmission, detection and identification.

Cryptosporidium and cryptosporidiosis in man and animals

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. baileyi, 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.

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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 baileyi, 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 Taxonomy: Recent Advances and Implications for Public Health (Review)

Eimeria spp. are the causative agents of coccidiosis, a major disease affecting many intensively-reared livestock, especially poultry. The chicken is host to 7 species of Eimeria that develop within intestinal epithelial cells and produce varying degrees of morbidity and mortality. Control of coccidiosis by the poultry industry is dominated by prophylactic chemotherapy but drug resistance is a serious problem. Strongly protective but species-specific immunity can be induced in chickens by infection with any of the Eimeria spp. At the Institute of Animal Health in Houghton, UK in the 1980s we showed that all 7 Eimeria spp. could be stably attenuated by serial passage in chickens of the earliest oocysts produced (i.e. the first parasites to complete their endogenous development) and this process resulted in the depletion of asexual development. Despite being highly attenuated, the precocious lines retained their immunizing capacity. Subsequent work led to the commercial introduction of the first live attenuated vaccine, Paracox®, that has now been in use for 20 years. As much work still remains to be done before the development of recombinant vaccines becomes a reality, it is likely that reliance upon live, attenuated vaccines will increase in years to come.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0031182009006349

Past and future: vaccination against Eimeria

Adult murine models of Cryptosporidium infection involving Cryptosporidium muris and C. parvum were used to study immunity to cryptosporidiosis in the mammalian host. Immunocompetent BALB/c or C57BL/6 mice developed a highly patent infection with the RN 66 strain of C. muris but overcame the infection and were immune to reinfection. In contrast, severe combined immunodeficiency (SCID) mice or nude mice had a chronic infection lasting at least 109 days. The development of the C. muris infection appeared to be confined to the gastric epithelium in immunocompetent and immunocompromised mice. SCID mice injected intraperitoneally with histocompatible spleen or mesenteric lymph node cells from uninfected BALB/c mice were able to recover from the C. muris infection. The protective effect of donor spleen cells was not reduced by depletion of the B cell population but was significantly reduced by depletion of Thy.1 cells. Treatment of C57BL/6 or BALB/c mice during infection with a gamma interferon-neutralizing monoclonal antibody, but not a tumor necrosis factor-neutralizing monoclonal antibody, resulted in a significant increase in oocyst production. In the C. parvum model, a severe and eventually fatal chronic infection with a cervine isolate was established in SCID mice, with parasitization occurring in the ileum, cecum, and colon. SCID mice injected with unprimed BALB/c spleen cells prior to inoculation of C. parvum oocysts were resistant to infection. These results suggested that the two animal models should be valuable in the study of immunity to cryptosporidial infection.

Immune responses to Cryptosporidium muris and Cryptosporidium parvum in adult immunocompetent or immunocompromised (nude and SCID) mice.

Cryopreparation of live sporozoites and oocysts of the apicomplexan parasite Cryptosporidium parvum, followed by transmission electron microscopy, was undertaken to show the 3D arrangement of organelles, their number and distribution. Profiles of parasites obtained from energy-filtering transmission electron microscopy of serial sections provided 3D reconstructions from which morphometric data and stereo images were derived. The results suggest that sporozoites have a single rhoptry containing an organized lamellar body, no mitochondria or conventional Golgi apparatus, and one or two crystalline bodies. Micronemes were shown to be spherical, numerous and apically located, and to account for 0.8% of the total cell volume. Dense granules were less numerous, larger, accounted for 5.8% of the cell volume, and were located more posteriorly than micronemes. A structure juxtaposed to the nucleus with similarities to the plastid-like organelle reported for other members of the Apicomplexa was observed. The detailed analysis illustrates the advantages of cryopreparation in retaining ultrastructural fidelity of labile or difficult to preserve structures such as the sporozoite of Cryptosporidium.

Ultrastructural analysis of the sporozoite of Cryptosporidium parvum

https://www.gastrojournal.org/article/S0016-5085(01)94403-8/pdf

Interferon gamma induces enterocyte resistance against infection by the intracellular pathogen Cryptosporidium parvum.

Invasion of enterocytes by pathogenic microbes evokes both innate and adaptive immune responses, and microbial pathogens have developed strategies to overcome the initial host immune defense. β-Defensins are potentially important endogenous antibiotic-like effectors of innate immunity expressed by intestinal epithelia. In this study, the interplay between the enteric protozoan parasite Cryptosporidium parvum and host epithelial β-defensin expression was investigated. Using human and murine models of infection, we demonstrated that C. parvum infection differentially regulates β-defensin gene expression. Downregulation of murine β-defensin-1 mRNA and protein was observed in both in vitro and in vivo models of infection. Infection of the human colonic HT29 cell line with the parasite resulted in differential effects on various members of the defensin gene family. Partial reduction in human β-defensin-1 (hBD-1), induction of hBD-2, and no effect on hBD-3 gene expression was observed. Recombinant hBD-1 and hBD-2 peptides exhibited significant antimicrobial activity against C. parvum sporozoites in vitro. These findings demonstrate that C. parvum infection of enterocytes may affect the expression of various defensins in different ways and suggest that the overall outcome of the effect of antimicrobial peptides on early survival of the parasite may be complex.

https://iai.asm.org/content/iai/72/5/2772.full.pdf

Vincent McDonald

Papers

Past and future: vaccination against Eimeria

Immune responses to Cryptosporidium muris and Cryptosporidium parvum in adult immunocompetent or immunocompromised (nude and SCID) mice.

Ultrastructural analysis of the sporozoite of Cryptosporidium parvum

Interferon gamma induces enterocyte resistance against infection by the intracellular pathogen Cryptosporidium parvum.

Differential regulation of beta-defensin gene expression during Cryptosporidium parvum infection.