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Lihua Xiao - One of the best experts on this subject based on the ideXlab platform.
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Cryptosporidium Genotyping for Epidemiology Tracking.
Methods in molecular biology (Clifton N.J.), 2019Co-Authors: Dawn M. Roellig, Lihua XiaoAbstract:Cryptosporidium genotyping has made significant contributions to the species structure and population genetics of Cryptosporidium spp. In addition, the standardized method has shown utility in epidemiologic investigations identifying case linkages and contamination sources that could not be determined with traditional epidemiologic tools. The standardized method for Cryptosporidium genotyping from stool specimens described here comprises multiple individual protocols to amplify and sequence regions of the SSU rRNA and gp60 genes of Cryptosporidium.
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distribution of Cryptosporidium species in tibetan sheep and yaks in qinghai china
Veterinary Parasitology, 2016Co-Authors: Jinzhong Cai, Yaoyu Feng, Mi Cai, Mengtong Lei, Liju Feng, Lihua XiaoAbstract:Few data are available on the distribution of Cryptosporidium species in Tibetan sheep and yaks, which are free-range animals living in a cold, low oxygen, and high ultraviolet radiation habitat. In this study, 904 fecal specimens were collected from 350 Tibetan sheep and 554 yaks in six counties. Cryptosporidium spp. were detected and differentiated by PCR and sequence analyses. Altogether, 43 (12.3%) Tibetan sheep and 158 (28.5%) yaks were positive for Cryptosporidium spp. In Tibetan sheep, Cryptosporidium xiaoi (39/43, 90.7%) was the dominant species, with the remaining cases (4/43, 9.3%) by Cryptosporidium ubiquitum. All C. ubiquitum specimens belonged to the subtype family XIIa. In contrast, Cryptosporidium andersoni (72/158, 45.6%), Cryptosporidium bovis (47/158, 29.7%), Cryptosporidium ryanae cattle type (35/158, 22.2%), C. ryanae buffalo type (2/158, 1.3%), and Cryptosporidium suis-like (2/158, 1.3%) were identified in yaks. Contradictory to previous observations, C. andersoni was one of the dominant Cryptosporidium species in yaks in this study. Despite sharing habitats, Tibetan sheep and yaks are evidently infected with different Cryptosporidium species.
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occurrence and molecular characterization of Cryptosporidium spp and enterocytozoon bieneusi in dairy cattle beef cattle and water buffaloes in china
Veterinary Parasitology, 2015Co-Authors: Xiaoping Zhao, Yaoyu Feng, Yuanfei Wang, Yaqiong Guo, Lin Wang, Lihua XiaoAbstract:Cryptosporidium spp. and Enterocytozoon bieneusi are important protists in a wide range of vertebrate hosts, causing diarrheal diseases. Cattle are considered potential reservoirs of Cryptosporidium infection in humans, although their role in the transmission of E. bieneusi is not clear. In the present work, 793 fecal specimens from dairy cattle, native beef cattle, and water buffaloes on 11 farms in China were examined for the presence of Cryptosporidium spp. and E. bieneusi using nested PCR targeting the small subunit (SSU) rRNA gene of Cryptosporidium spp. and the internal transcribed spacer (ITS) of E. bieneusi. For Cryptosporidium, 144/446 (32.3%) dairy cattle, 44/166 (26.5%) beef cattle, and 43/181 (23.8%) water buffaloes were PCR-positive. Sequence analysis was successful for 213 of the 231 Cryptosporidium-positive isolates; among them 94 had Cryptosporidium andersoni, 61 had Cryptosporidium bovis, 54 had Cryptosporidium ryanae, 2 had a Cryptosporidium suis-like genotype, and 2 had mixed infections of C. bovis and C. ryanae. In dairy and beef cattle, C. andersoni and C. bovis were the most common species, whereas C. ryanae was the dominant species in water buffaloes. The latter species produced SSU rRNA sequences different between cattle and water buffaloes. For E. bieneusi, the infection rate of E. bieneusi in dairy cattle, beef cattle and water buffaloes was 4.9%, 5.4% and 2.2%, respectively. All 35 E. bieneusi-positive specimens were successfully sequenced, revealing the presence of four genotypes: three Group 2 genotypes previously reported in cattle as well as humans (I, J and BEB4) and one Group 1 genotype recently reported in yaks (CHN11). Genotypes I and J were the most common genotypes in dairy and beef cattle, while genotype CHN11 was the only genotype seen in water buffaloes. Thus, the distribution of Cryptosporidium spp. and E. bieneusi in water buffaloes might be different from in dairy and beef cattle in China. These findings indicate that some of the Cryptosporidium species and all four E. bieneusi genotypes identified in bovine animals in the study areas may have zoonotic potential.
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Cryptosporidium species in humans and animals current understanding and research needs
Parasitology, 2014Co-Authors: Una Ryan, Ronald Fayer, Lihua XiaoAbstract:Cryptosporidium is increasingly recognized as one of the major causes of moderate to severe diarrhoea in developing countries. With treatment options limited, control relies on knowledge of the biology and transmission of the members of the genus responsible for disease. Currently, 26 species are recognized as valid on the basis of morphological, biological and molecular data. Of the nearly 20 Cryptosporidium species and genotypes that have been reported in humans, Cryptosporidium hominis and Cryptosporidium parvum are responsible for the majority of infections. Livestock, particularly cattle, are one of the most important reservoirs of zoonotic infections. Domesticated and wild animals can each be infected with several Cryptosporidium species or genotypes that have only a narrow host range and therefore have no major public health significance. Recent advances in next-generation sequencing techniques will significantly improve our understanding of the taxonomy and transmission of Cryptosporidium species, and the investigation of outbreaks and monitoring of emerging and virulent subtypes. Important research gaps remain including a lack of subtyping tools for many Cryptosporidium species of public and veterinary health importance, and poor understanding of the genetic determinants of host specificity of Cryptosporidium species and impact of climate change on the transmission of Cryptosporidium.
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minimal zoonotic risk of cryptosporidiosis from pet dogs and cats
Trends in Parasitology, 2010Co-Authors: Araceli Lucioforster, Vitaliano Cama, Lihua Xiao, Jeffrey K Griffiths, Dwight D BowmanAbstract:The role of dogs and cats in human cryptosporidiosis has been the focus of much attention. Studies in which genotyping of Cryptospiridium oocysts in feces of dogs and cats have been successful and have demonstrated that most infections in these animals are caused by host-specific C. canis and C. felis, respectively. Most human cases of cryptosporidiosis are associated with C. hominis and C. parvum; C. canis and C. felis are responsible for only a small number of cases. Thus, molecular epidemiologic studies support the contention that the risk of zoonotic transmission of Cryptosporidium spp. from pet cats and dogs is low. Veterinarians can inform their clients of this minimal risk, but nevertheless advise them to minimize contact with pet cat and dog feces.
Altaf A. Lal - One of the best experts on this subject based on the ideXlab platform.
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Detection and Differentiation of Cryptosporidium Oocysts in Water by PCR-RFLP
Methods of Molecular Biology, 2004Co-Authors: Lihua Xiao, Altaf A. Lal, Jianlin JiangAbstract:Consumption of contaminated water has been implicated as a major source of Cryptosporidium infection in various outbreak investigations and case control studies. Surveys conducted in various regions of the United States demonstrated the presence of Cryptosporidium oocysts in 67-100% of wastewaters, 24-100% of surface waters, and 17-26.8% of drinking waters. The identity and human infective potential of these waterborne oocysts are not known, although it is likely that not all oocysts are from human-infecting Cryptosporidium species. Likewise, the source of the oocyst contamination is also not fully clear. Farm animals and human sewage discharge are generally considered to be the major sources of surface water contamination with C. parvum. Because Cryptosporidium infection is common in wildlife, it is conceivable that wildlife can also be a source for Cryptosporidium oocysts in waters. The presence of host-adapted Cryptosporidium spp. and genotypes makes it possible to develop molecular tools to assess the human infection potential and source of Cryptosporidium oocysts in water.Currently, the identification of Cryptosporidium oocysts in environmental samples is largely made by the use of immunofluorescent assay (IFA) after concentration processes (Environmental Protection Agency [EPA] recommended information collection rule [ICR] method or method 1622/1623 or similar techniques). Because IFA detects oocysts from all Cryptosporidium parasites, the species distribution of Cryptosporidium parasites in environmental samples cannot be assessed. Although many surface water samples contain Cryptosporidium oocysts, it is unlikely that all these oocysts are from human-pathogenic species or genotypes, because only five genotypes of Cryptosporidium parasites (the C. parvum human and bovine genotypes, C. meleagridis, C. canis, and C. felis) are responsible for most human infections. Information on the source of C. parvum contamination is necessary for effective evaluation and selection of management practices for reducing C. parvum contamination of surface water and the risk of cryptosporidiosis. Thus, identification of oocysts to species and genotype levels is of public health importance.
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host adaptation and host parasite co evolution in Cryptosporidium implications for taxonomy and public health
International Journal for Parasitology, 2002Co-Authors: Lihua Xiao, Una Ryan, Ling Zhou, Irshad M Sulaiman, Edward R Atwill, Monica Lee Tischler, Xichen Zhang, Ronald Fayer, Altaf A. LalAbstract:To assess the genetic diversity and evolution of Cryptosporidium parasites, the partial ssrRNA, actin, and 70 kDa heat shock protein (HSP70) genes of 15 new Cryptosporidium parasites were sequenced. Sequence data were analysed together with those previously obtained from other Cryptosporidium parasites (10 Cryptosporidium spp. and eight Cryptosporidium genotypes). Results of this multi-locus genetic characterisation indicate that host adaptation is a general phenomenon in the genus Cryptosporidium, because specific genotypes were usually associated with specific groups of animals. On the other hand, host-parasite co-evolution is also common in Cryptosporidium, as closely related hosts usually had related Cryptosporidium parasites. Results of phylogenetic analyses suggest that the Cryptosporidium parvum bovine genotype and Cryptosporidium meleagridis were originally parasites of rodents and mammals, respectively, but have subsequently expanded their host ranges to include humans. Understanding the evolution of Cryptosporidium species is important not only for clarification of the taxonomy of the parasites but also for assessment of the public health significance of Cryptosporidium parasites from animals.
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Molecular characterization of Cryptosporidium oocysts in samples of raw surface water and wastewater.
Applied and Environmental Microbiology, 2001Co-Authors: Lihua Xiao, Thaddeus K Graczyk, Josef Limor, Ajaib Singh, Steve Graduss. Gradus, Altaf A. LalAbstract:Recent molecular characterizations of Cryptosporidium parasites make it possible to differentiate the human-pathogenic Cryptosporidium parasites from those that do not infect humans and to track the source of Cryptosporidium oocyst contamination in the environment. In this study, we used a small-subunit rRNA-based PCR-restriction fragment length polymorphism (RFLP) technique to detect and characterize Cryptosporidium oocysts in 55 samples of raw surface water collected from several areas in the United States and 49 samples of raw wastewater collected from Milwaukee, Wis. Cryptosporidium parasites were detected in 25 surface water samples and 12 raw wastewater samples. C. parvum human and bovine genotypes were the dominant Cryptosporidium parasites in the surface water samples from sites where there was potential contamination by humans and cattle, whereas C. andersoni was the most common parasite in wastewater. There may be geographic differences in the distribution of Cryptosporidium genotypes in surface water. The PCR-RFLP technique can be a useful alternative method for detection and differentiation of Cryptosporidium parasites in water.
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phylogenetic analysis of Cryptosporidium parasites based on the small subunit rrna gene locus
Applied and Environmental Microbiology, 1999Co-Authors: Lihua Xiao, Irshad M Sulaiman, Ronald Fayer, Lillian Escalante, Chunfu Yang, Anannias A Escalante, Richard J Montali, Altaf A. LalAbstract: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.
Una Ryan - One of the best experts on this subject based on the ideXlab platform.
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New developments in Cryptosporidium research
International journal for parasitology, 2015Co-Authors: Una Ryan, Nawal HijjawiAbstract:Cryptosporidium is an enteric parasite that is considered the second greatest cause of diarrhoea and death in children after rotavirus. Currently, 27 species are recognised as valid and of these, Cryptosporidium hominis and Cryptosporidium parvum are responsible for the majority of infections in humans. Molecular and biological studies indicate that Cryptosporidium is more closely related to gregarine parasites rather than to coccidians. The identification of gregarine-like gamont stages and the ability of Cryptosporidium to complete its life cycle in the absence of host cells further confirm its relationship with gregarines. This opens new avenues into the investigation of pathogenesis, epidemiology, treatment and control of Cryptosporidium. Effective drug treatments and vaccines are not yet available due, in part, to the technical challenges of working on Cryptosporidium in the laboratory. Whole genome sequencing and metabolomics have expanded our understanding of the biochemical requirements of this organism and have identified new drug targets. To effectively combat this important pathogen, increased funding is essential.
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Cryptosporidium species in humans and animals current understanding and research needs
Parasitology, 2014Co-Authors: Una Ryan, Ronald Fayer, Lihua XiaoAbstract:Cryptosporidium is increasingly recognized as one of the major causes of moderate to severe diarrhoea in developing countries. With treatment options limited, control relies on knowledge of the biology and transmission of the members of the genus responsible for disease. Currently, 26 species are recognized as valid on the basis of morphological, biological and molecular data. Of the nearly 20 Cryptosporidium species and genotypes that have been reported in humans, Cryptosporidium hominis and Cryptosporidium parvum are responsible for the majority of infections. Livestock, particularly cattle, are one of the most important reservoirs of zoonotic infections. Domesticated and wild animals can each be infected with several Cryptosporidium species or genotypes that have only a narrow host range and therefore have no major public health significance. Recent advances in next-generation sequencing techniques will significantly improve our understanding of the taxonomy and transmission of Cryptosporidium species, and the investigation of outbreaks and monitoring of emerging and virulent subtypes. Important research gaps remain including a lack of subtyping tools for many Cryptosporidium species of public and veterinary health importance, and poor understanding of the genetic determinants of host specificity of Cryptosporidium species and impact of climate change on the transmission of Cryptosporidium.
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Human Cryptosporidiosis Diagnosed in Western Australia: a Mixed Infection with Cryptosporidium meleagridis, the Cryptosporidium Mink Genotype, and an Unknown Cryptosporidium Species
Journal of clinical microbiology, 2013Co-Authors: Josephine Ng-hublin, B.g. Combs, Brian Mackenzie, Una RyanAbstract:This report describes a case of cryptosporidiosis from an immunocompetent patient from Perth, Western Australia, suffering from diarrhea and a spectrum of other symptoms. Molecular identification revealed that this patient was infected with three Cryptosporidium species-Cryptosporidium meleagridis, the Cryptosporidium mink genotype, and an unknown Cryptosporidium species.
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identification of novel Cryptosporidium genotypes from avian hosts
Applied and Environmental Microbiology, 2006Co-Authors: Ivan Pavlasek, Una RyanAbstract:A total of 430 avian-derived fecal specimens were randomly collected from selected Western Australian commercial aviaries, poultry farms, hatcheries, wildlife parks, and the Perth Zoo and screened for the presence of Cryptosporidium by PCR. Of these, 27 Cryptosporidium-positive isolates were detected, characterized, and compared with 11 avian-derived isolates from the Czech Republic at the 18S rRNA and actin gene loci. Sequence and phylogenetic analysis identified four genetically distinct genotypes, avian genotypes I to IV, from various avian hosts. In addition, the host range for Cryptosporidium galli was extended. Cryptosporidium muris and Cryptosporidium andersoni were also identified in a tawny frogmouth and a quail-crested wood partridge, respectively.
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Cryptosporidium suis n sp apicomplexa cryptosporidiidae in pigs sus scrofa
Journal of Parasitology, 2004Co-Authors: Una Ryan, Heidi Larsen Enemark, I Sulaiman, Buddhini Samarasinghe, Carolyn Read, Ross Buddle, Paul Monis, I.d. Robertson, L Zhou, R C A ThompsonAbstract:Molecular and biological characteristics of a new species of Cryptosporidium from the feces of pigs (Sus scrofa) is described. Oocysts are structurally indistinguishable from those of Cryptosporidium parvum; they are passed fully sporulated, lack sporocysts, and measure 4.9–4.4 μm (mean = 4.6 μm) × 4.0–4.3 μm (mean = 4.2 μm); length to width ratio 1.1 (n = 50). Cryptosporidium suis is not transmissible to nude mice and is poorly infectious for cattle. Molecular and phylogenetic analyses at the 18S ribosomal RNA, heat shock protein 70, and actin gene loci demonstrate C. suis to be genetically distinct from all known species and genotypes of Cryptosporidium, and thus is named as Cryptosporidium suis.
J Mclauchlin - One of the best experts on this subject based on the ideXlab platform.
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genetic analysis of Cryptosporidium from 2414 humans with diarrhoea in england between 1985 and 2000
Journal of Medical Microbiology, 2006Co-Authors: Francesca Leoni, C Amar, Gordon Nichols, Susana Pedrazadiaz, J MclauchlinAbstract:The characterization of Cryptosporidium using DNA extracted from whole faecal samples collected from 2414 humans with diarrhoea in England between 1985 and 2000 where cryptosporidial oocysts were detected using conventional methods is described. Characterization was achieved by PCR/RFLP and DNA sequencing of fragments of the Cryptosporidium oocyst wall protein and the 18S rDNA genes. Cryptosporidium parvum was detected in 56.1 % of cases, Cryptosporidium hominis in 41.7 % and a mixture of C. parvum and C. hominis in 0.9 %. In the remainder of cases, Cryptosporidium meleagridis (0.9 %), Cryptosporidium felis (0.2 %), Cryptosporidium andersoni (0.1 %), Cryptosporidium canis (0.04 %), Cryptosporidium suis (0.04 %) and the Cryptosporidium cervine type (0.04 %) were detected.
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The identification of Cryptosporidium species and Cryptosporidium parvum directly from whole faeces by analysis of a multiplex PCR of the 18S rRNA gene and by PCR/RFLP of the Cryptosporidium outer wall protein (COWP) gene
International journal for parasitology, 1999Co-Authors: S Patel, S Pedraza-dı́az, J MclauchlinAbstract:Abstract A multiplex polymerase chain reaction (PCR) procedure to amplify 18S rRNA gene fragments has been developed. Amplified DNA fragments of the expected size were obtained which were specific for Cryptosporidium parvum and Cryptosporidium wrairi (422 bp), Cryptosporidium baileyi (1106 bp) and Cryptosporidium muris (1346 bp). Cryptosporidium parvum and C. wrairi can be distinguished using a PCR/restriction fragment length polymorphism (RFLP) analysis of the Cryptosporidium outer wall protein (COWP) gene, and these two techniques were applied to DNA extracted from whole faeces using a simple and rapid procedure. Cryptosporidium parvum DNA was detected in the faeces of 72 humans and 24 calves where cryptosporidial oocysts were demonstrated using conventional light microscopy. The specific DNA fragments were not amplified using extracts of material containing other lower eukaryotic parasites.
Ronald Fayer - One of the best experts on this subject based on the ideXlab platform.
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Cryptosporidium species in humans and animals current understanding and research needs
Parasitology, 2014Co-Authors: Una Ryan, Ronald Fayer, Lihua XiaoAbstract:Cryptosporidium is increasingly recognized as one of the major causes of moderate to severe diarrhoea in developing countries. With treatment options limited, control relies on knowledge of the biology and transmission of the members of the genus responsible for disease. Currently, 26 species are recognized as valid on the basis of morphological, biological and molecular data. Of the nearly 20 Cryptosporidium species and genotypes that have been reported in humans, Cryptosporidium hominis and Cryptosporidium parvum are responsible for the majority of infections. Livestock, particularly cattle, are one of the most important reservoirs of zoonotic infections. Domesticated and wild animals can each be infected with several Cryptosporidium species or genotypes that have only a narrow host range and therefore have no major public health significance. Recent advances in next-generation sequencing techniques will significantly improve our understanding of the taxonomy and transmission of Cryptosporidium species, and the investigation of outbreaks and monitoring of emerging and virulent subtypes. Important research gaps remain including a lack of subtyping tools for many Cryptosporidium species of public and veterinary health importance, and poor understanding of the genetic determinants of host specificity of Cryptosporidium species and impact of climate change on the transmission of Cryptosporidium.
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prevalence of species and genotypes of Cryptosporidium found in 1 2 year old dairy cattle in the eastern united states
Veterinary Parasitology, 2006Co-Authors: Ronald Fayer, Monica Santin, James M Trout, Ellis C GreinerAbstract:The prevalence of Cryptosporidium species in 1-2-year-old heifers was determined for 571 animals on 14 dairy farms in seven states on the East Coast of the United States. A fecal specimen collected directly from each heifer was processed to concentrate oocysts that were then examined by polymerase chain reaction (PCR). For every PCR-positive specimen the 18S rRNA gene of Cryptosporidium was sequenced. Cryptosporidium was identified by PCR from heifers on 13 of 14 farms. On all except four farms groups of heifers were housed in a barn or in large covered pens. Others were pastured. From many of the same farms an earlier study reported that 41% of 393 pre-weaned calves and 26.2% of 447 post-weaned calves were infected. In the present study, 11.9% of 571 heifers were infected with Cryptosporidium, 0.7% with Cryptosporidium parvum, the zoonotic species. Of 68 PCR-positive specimens characterized by gene sequencing 1, 4, 10, 24, and 29 calves were infected with Cryptosporidium suis, Cryptosporidium parvum, Cryptosporidium deer-like genotype, Cryptosporidium bovis, and Cryptosporidium andersoni, respectively. These findings demonstrate a lower prevalence of infection in 1-2-year-old dairy cattle than in younger cattle as well as a change in the diversity of species present. Consequently, the risk of humans acquiring infection with C. parvum from exposure to feces from yearling and older cattle appears much lower than from exposure to pre-weaned calves.
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prevalence and age related variation of Cryptosporidium species and genotypes in dairy calves
Veterinary Parasitology, 2004Co-Authors: Monica Santin, Lihua Xiao, Ling Zhou, James M Trout, Ellis C Greiner, Ronald FayerAbstract:Fifteen dairy farms in seven states on the east coast of the US were each visited on two consecutive years to determinate the prevalence of Cryptosporidium species in pre-weaned (5 days to 2 months) and post-weaned calves (3-11 months), respectively. After each of 971 fecal specimens collected directly from each calf was sieved and subjected to density gradient centrifugation to remove debris and concentrate oocysts, specimens were examined by immunofluorescence microscopy, and polymerase chain reaction (PCR). For all PCR-positive specimens the 18S rRNA gene of Cryptosporidium was sequenced. Cryptosporidium was identified from all farms. Types of housing appeared to have no influence with regard to prevalence of infection. Of 971 calves, 345 were infected with Cryptosporidium (35.5%), but more pre-weaned calves (253 of 503; 50.3%) than post-weaned calves (92 of 468; 19.7%) were found to be infected. A total of 278 PCR-positive specimens characterized by gene sequencing revealed Cryptosporidium parvum, Cryptosporidium andersoni, and two unnamed Cryptosporidium genotypes Bovine B (AY120911) and deer-like genotype (AY120910). The prevalence of these Cryptosporidium species and genotypes appeared to be age related between pre- and post-weaned calves. C. parvum, the only zoonotic species/genotype, constituted 85% of the Cryptosporidium infections in pre-weaned calves but only 1% of the Cryptosporidium infections in post-weaned calves. These findings clearly demonstrate that earlier reports on the presence and prevalence of C. parvum in post-weaned cattle that were based solely on oocyst morphology must be reassessed using molecular methods to validate species and genotype. This finding also indicates that persons handling or otherwise exposed to calves under 2 months of age are at greater risk of zoonotic infection from Cryptosporidium than the risk of infection from exposure to older calves.
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Cryptosporidium taxonomy recent advances and implications for public health
Clinical Microbiology Reviews, 2004Co-Authors: Lihua Xiao, Una Ryan, Ronald Fayer, Steve J UptonAbstract: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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host adaptation and host parasite co evolution in Cryptosporidium implications for taxonomy and public health
International Journal for Parasitology, 2002Co-Authors: Lihua Xiao, Una Ryan, Ling Zhou, Irshad M Sulaiman, Edward R Atwill, Monica Lee Tischler, Xichen Zhang, Ronald Fayer, Altaf A. LalAbstract:To assess the genetic diversity and evolution of Cryptosporidium parasites, the partial ssrRNA, actin, and 70 kDa heat shock protein (HSP70) genes of 15 new Cryptosporidium parasites were sequenced. Sequence data were analysed together with those previously obtained from other Cryptosporidium parasites (10 Cryptosporidium spp. and eight Cryptosporidium genotypes). Results of this multi-locus genetic characterisation indicate that host adaptation is a general phenomenon in the genus Cryptosporidium, because specific genotypes were usually associated with specific groups of animals. On the other hand, host-parasite co-evolution is also common in Cryptosporidium, as closely related hosts usually had related Cryptosporidium parasites. Results of phylogenetic analyses suggest that the Cryptosporidium parvum bovine genotype and Cryptosporidium meleagridis were originally parasites of rodents and mammals, respectively, but have subsequently expanded their host ranges to include humans. Understanding the evolution of Cryptosporidium species is important not only for clarification of the taxonomy of the parasites but also for assessment of the public health significance of Cryptosporidium parasites from animals.