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)

Summary Cryptosporidium spp are well recognised as causes of diarrhoeal disease during waterborne epidemics and in immunocompromised hosts. Studies have also drawn attention to an underestimated global burden and suggest major gaps in optimum diagnosis, treatment, and immunisation. Cryptosporidiosis is increasingly identified as an important cause of morbidity and mortality worldwide. Studies in low-resource settings and high-income countries have confirmed the importance of cryptosporidium as a cause of diarrhoea and childhood malnutrition. Diagnostic tests for cryptosporidium infection are suboptimum, necessitating specialised tests that are often insensitive. Antigen-detection and PCR improve sensitivity, and multiplexed antigen detection and molecular assays are underused. Therapy has some effect in healthy hosts and no proven efficacy in patients with AIDS. Use of cryptosporidium genomes has helped to identify promising therapeutic targets, and drugs are in development, but methods to assess the efficacy in vitro and in animals are not well standardised. Partial immunity after exposure suggests the potential for successful vaccines, and several are in development; however, surrogates of protection are not well defined. Improved methods for propagation and genetic manipulation of the organism would be significant advances.

/pdf/a-review-of-the-global-burden-novel-diagnostics-therapeutics-ujw4dop0op.pdf

A review of the global burden, novel diagnostics, therapeutics, and vaccine targets for cryptosporidium

Molecular characterisation of species and genotypes of Cryptosporidium and Giardia and assessment of zoonotic transmission

To understand the transmission of Cryptosporidium infection in children, fecal specimens from 62 Kuwaiti children with gastrointestinal symptoms found to be positive by microscopy were genotyped and subtyped with a small subunit rRNA-based PCR-restriction fragment length polymorphism analysis and a 60-kDa glycoprotein-based DNA sequencing tool. The median age of infected children was 4.5 years, and 77% of infections occurred during the cool season of November to April. Fifty-eight of the children (94%) had Cryptosporidium parvum, three (5%) had Cryptosporidium hominis, and one (1%) had both C. parvum and C. hominis. Altogether, 13 subtypes of C. parvum (belonging to four subtype allele families) and C. hominis (belonging to three subtype allele families) were observed, with 92% of specimens belonging to the common allele family IIa and the unusual allele family IId. Thus, the transmission of cryptosporidiosis in Kuwaiti children differed significantly from other tropical countries.

https://jcm.asm.org/content/jcm/43/6/2805.full.pdf

Unique Endemicity of Cryptosporidiosis in Children in Kuwait

A cross-sectional case-control study (ratio = 3:1) was conducted over a 15-month period to determine the prevalence and consequences of cryptosporidiosis in hospitalized diarrheic children (0–5 years old) at Mulago Hospital in Kampala, Uganda. Cryptosporidium parvum was detected and genotyped among 2,446 children of whom 1,779 (72.7%) had diarrhea, and 667 (27.3%) were age- and sex-matched controls. Of the 1,779 children with diarrhea, 532 (29.9%) had persistent (> 14 days) diarrhea and 1,247 (70.1%) had acute diarrhea. Overall, 444 (25.0%) of the 1,779 children with diarrhea had C. parvum, compared with only 57 (8.5%) of the 667 children without diarrhea (χ2 = 80.2, P ≤ 0.0001). Within this group of infected children, 72.8% were infected with genotype 1, 18.4% with genotype 2, and 4.1% with a mixture of both genotypes, and 4.1% isolates were either unclassified or C. meleagridis. The prevalence was highest during the rainy months of April to June. Of the 532 children with persistent diarrhea, 166 (31.2%) had C. parvum compared with 278 (22.3%) of the 1,247 children with acute diarrhea (χ2 = 15.8, P ≤ 0.0001). There was a significant association between C. parvum and malnutrition including stunting, being underweight, and wasting. Unfavorable outcome (death or failure to resolve within 14 days) occurred in 139 (72.8%) of the 191 children with C. parvum, and in only 65.1% of the 545 without (odds ratio = 1.117, 95% confidence interval = 1.005–1.243, P = 0.05), Of the 191 children with C. parvum, 24 (12.6%) died, compared with 34 (6.2%) of the 545 without C. parvum (P = 0.005). Mortality rates were higher among children with severe dehydration and persistent diarrhea, and in stunted or underweight children infected with C. parvum. Among Ugandan children, cryptosporidiosis, which remains untreatable, is frequently associated with diarrhea and other serious and unfavorable consequences.

Cryptosporidium parvum in children with diarrhea in Mulago Hospital, Kampala, Uganda.

The prevalence of Enterocytozoon bieneusi in the general population is unknown. Using genetic tools, we investigated its prevalence and contribution to diarrhea and malnutrition in hospitalized children in Uganda. A cross-sectional, case-control study involving diarrheic children who were matched for age and sex (3:1) with control children. Measurements included anthropometry and clinical assessment. A total of 17.4% of 1,779 children with diarrhea were infected with E. bieneusi compared with 16.8% of 667 control children (CHI2 = 0.137, P = 0.712). Prevalence was highest during the rainy seasons. There was no significant relationship between infection with E. bieneusi and stunting, being underweight, wasting, or acute diarrhea. However, children who were E. bieneusi-positive by a polymerase chain reaction (PCR) had diarrhea for a longer period (15.15 versus 9.67 days; F = 12.02; P = 0.001) compared with children who were either uninfected or were E. bieneusi-positive by a nested PCR. We conclude that E. bieneusi is widespread among children 3-36 months of age in Uganda, and that in a cross-sectional study, there was no clear association of E. bieneusi with poor nutrition or diarrhea. Since E. bieneusi is closely linked with persistent diarrhea and wasting in adults who are positive for human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), the outcome of follow-up studies involving children who are HIV/AIDS-positive and severely malnourished children may be entirely different and warrants further study.

Enterocytozoon bieneusi among children with diarrhea attending Mulago Hospital in Uganda.

Restriction fragment length polymorphism and DNA sequence analysis discern two main types of Cryptosporidium parvum. We present a survey of length polymorphism at several microsatellite loci for type 1 and type 2 isolates. A total of 14 microsatellite loci were identified from C. parvum DNA sequences deposited in public databases. All repeats were mono-, di-, and trinucleotide repeats of A, AT, and AAT, reflecting the high AT content of the C. parvum genome. Several of these loci showed significant length polymorphism, with as many as seven alleles identified for a single locus. Differences between alleles ranged from 1 to 27 bp. Karyotype analysis using probes flanking three microsatellites localized each marker to an individual chromosomal band, suggesting that these markers are single copy. In a sample of 19 isolates for which at least three microsatellites were typed, a majority of isolates displayed a unique multilocus fingerprint. Microsatellite analysis of isolates passaged between different host species identified genotypic changes consistent with changes in parasite populations.

Nicolette Nabukeera

Papers

Cryptosporidium parvum in children with diarrhea in Mulago Hospital, Kampala, Uganda.

Enterocytozoon bieneusi among children with diarrhea attending Mulago Hospital in Uganda.

Extensive polymorphism in Cryptosporidium parvum identified by multilocus microsatellite analysis.