Epidemiology of Cryptosporidium: transmission, detection and identification.

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)

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.

Phylogenetic Analysis of Cryptosporidium Parasites Based on the Small-Subunit rRNA Gene Locus

To assess the genetic diversity in Cryptosporidium parvum, we have sequenced the small subunit (SSU) rRNA gene of seven Cryptosporidium spp., various isolates of C. parvum from eight hosts, and a Cryptosporidium isolate from a desert monitor. Phylogenetic analysis of the SSU rRNA sequences confirmed the multispecies nature of the genus Cryptosporidium, with at least four distinct species (C. parvum, C. baileyi, C. muris, and C. serpentis). Other species previously defined by biologic characteristics, including C. wrairi, C. meleagridis, and C. felis, and the desert monitor isolate, clustered together or within C. parvum. Extensive genetic diversities were present among C. parvum isolates from humans, calves, pigs, dogs, mice, ferrets, marsupials, and a monkey. In general, specific genotypes were associated with specific host species. A PCR-restriction fragment length polymorphism technique previously developed by us could differentiate most Cryptosporidium spp. and C. parvum genotypes, but sequence analysis of the PCR product was needed to differentiate C. wrairi and C. meleagridis from some of the C. parvum genotypes. These results indicate a need for revision in the taxonomy and assessment of the zoonotic potential of some animal C. parvum isolates.

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Genetic diversity within cryptosporidium parvum and related cryptosporidium species

In order to define transmission routes of cryptosporidiosis and develop markers that distinguish Cryptosporidium parvum isolates, we have identified 2 polymorphic restriction enzyme sites in a C. parvum repetitive DNA sequence. The target sequence was amplified by polymerase chain reaction from 100 to 500 oocysts and the amplified product was subjected to restriction enzyme digestion. Typing of 23 isolates showed that 10 / 10 calf isolates had the same profile. In contrast, 2 patterns were observed among human isolates: 7 / 13 displayed the calf profile, and 6 / 13 presented another pattern. The PCR-RFLP assay described here is a sensitive tool to distinguish C. parvum isolates.

Genotyping human and bovine isolates of Cryptosporidium parvum by polymerase chain reaction‐restriction fragment length polymorphism analysis of a repetitive DNA sequence

Dominique Puygauthier-Toubas

Papers

Genotyping human and bovine isolates of Cryptosporidium parvum by polymerase chain reaction‐restriction fragment length polymorphism analysis of a repetitive DNA sequence