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      Molecular Epidemiology of Cryptosporidiosis in China

      review-article
      1 , 2
      Frontiers in Microbiology
      Frontiers Media S.A.
      cryptosporidiosis, Cryptosporidium, molecular epidemiology, zoonosis, China

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          Abstract

          Molecular epidemiology of cryptosporidiosis is an active research area in China. The use of genotyping and subtyping tools in prevalence studies has led to the identification of unique characteristics of Cryptosporidium infections in humans and animals. Human cryptosporidiosis in China is exemplified by the high diversity of Cryptosporidium spp. at species and subtype levels, with dominant C. hominis and C. parvum subtypes being rarely detected in other countries. Similarly, preweaned dairy calves, lambs, and goat kids are mostly infected with non-pathogenic Cryptosporidium species ( C. bovis in calves and C. xiaoi in lambs and goat kids), with C. parvum starting to appear in dairy calves as a consequence of concentrated animal feeding operations. The latter Cryptosporidium species is dominated by IId subtypes, with IIa subtypes largely absent from the country. Unlike elsewhere, rodents in China appear to be commonly infected with C. parvum IId subtypes, with identical subtypes being found in these animals, calves, other livestock, and humans. In addition to cattle, pigs and chickens appear to be significant contributors to Cryptosporidium contamination in drinking water sources, as reflected by the frequent detection of C. suis, C. baileyi, and C. meleagridis in water samples. Chinese scientists have also made significant contributions to the development of new molecular epidemiological tools for Cryptosporidium spp. and improvements in our understanding of the mechanism involved in the emergence of hyper-transmissible and virulent C. hominis and C. parvum subtypes. Despite this progress, coordinated research efforts should be made to address changes in Cryptosporidium transmission because of rapid economic development in China and to prevent the introduction and spread of virulent and zoonotic Cryptosporidium species and subtypes in farm animals.

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          Cryptosporidium species in humans and animals: current understanding and research needs.

          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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            Genetic modification of the diarrheal pathogen Cryptosporidium parvum

            Recent studies into the global causes of severe diarrhea in young children have identified the protozoan parasite Cryptosporidium as the second most important diarrheal pathogen after rotavirus 1–3 . Diarrheal disease is estimated to be responsible for 10.5% of overall child mortality 4 . Cryptosporidium is also an opportunistic pathogen in the context of HIV-AIDS and organ transplantation 5,6 . There is no vaccine and only a single approved drug that provides no benefit for those in gravest danger, malnourished children and immunocompromised patients 7,8 . Cryptosporidiosis drug and vaccine development is limited by the poor tractability of the parasite, which includes lack of continuous culture, facile animal models, and molecular genetic tools 3,9 . Here we describe an experimental framework to genetically modify this important human pathogen. We establish and optimize transfection of C. parvum sporozoites in tissue culture. To isolate stable transgenics we develop a mouse model that delivers sporozoites directly into the intestine, a Cryptosporidium CRISPR/Cas9 system, and in vivo selection for aminoglycoside resistance. We derive reporter parasites suitable for in vitro and in vivo drug screening, and we evaluate the basis of drug susceptibility by gene knock out. We anticipate the ability to genetically engineer the parasite will be transformative for Cryptosporidium research. Genetic reporters will provide quantitative correlates for disease, cure and protection and the role of parasite genes in these processes is now open to rigorous investigation.
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              Zoonotic Cryptosporidium species and Enterocytozoon bieneusi genotypes in HIV-positive patients on antiretroviral therapy.

              Molecular diagnostic tools have been used increasingly in the characterization of the transmission of cryptosporidiosis and microsporidiosis in developing countries. However, few studies have examined the distribution of Cryptosporidium species and Enterocytozoon bieneusi genotypes in AIDS patients receiving antiretroviral therapy. In the present study, 683 HIV-positive patients in the National Free Antiretroviral Therapy Program in China and 683 matched HIV-negative controls were enrolled. Cryptosporidium species and subtypes and Enterocytozoon bieneusi genotypes were detected and differentiated by PCR and DNA sequencing. The infection rates were 1.5% and 0.15% for Cryptosporidium and 5.7% and 4.2% for E. bieneusi in HIV-positive and HIV-negative participants, respectively. The majority (8/11) of Cryptosporidium cases were infections by zoonotic species, including Cryptosporidium meleagridis (5), Cryptosporidium parvum (2), and Cryptosporidium suis (1). Prevalent E. bieneusi genotypes detected, including EbpC (39), D (12), and type IV (7), were also potentially zoonotic. The common occurrence of EbpC was a feature of E. bieneusi transmission not seen in other areas. Contact with animals was a risk factor for both cryptosporidiosis and microsporidiosis. The results suggest that zoonotic transmission was significant in the epidemiology of both diseases in rural AIDS patients in China.
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                Author and article information

                Contributors
                Journal
                Front Microbiol
                Front Microbiol
                Front. Microbiol.
                Frontiers in Microbiology
                Frontiers Media S.A.
                1664-302X
                06 September 2017
                2017
                : 8
                : 1701
                Affiliations
                [1] 1College of Veterinary Medicine, South China Agricultural University Guangzhou, China
                [2] 2Division of Foodborne, Waterborne and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention Atlanta, GA, United States
                Author notes

                Edited by: Wei Hu, Fudan University, China

                Reviewed by: Mingbo Yin, Fudan University, China; Jiaxu Chen, National Institute of Parasitic Diseases, China

                *Correspondence: Yaoyu Feng yyfeng@ 123456scau.edu.cn

                This article was submitted to Infectious Diseases, a section of the journal Frontiers in Microbiology

                Article
                10.3389/fmicb.2017.01701
                5592218
                28932217
                bf667a54-2ee9-4890-b532-7ccb499ad83e
                Copyright © 2017 Feng and Xiao.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 28 April 2017
                : 23 August 2017
                Page count
                Figures: 0, Tables: 4, Equations: 0, References: 147, Pages: 11, Words: 10116
                Funding
                Funded by: National Natural Science Foundation of China 10.13039/501100001809
                Award ID: 31425025
                Award ID: 31630078
                Categories
                Microbiology
                Review

                Microbiology & Virology
                cryptosporidiosis,cryptosporidium,molecular epidemiology,zoonosis,china
                Microbiology & Virology
                cryptosporidiosis, cryptosporidium, molecular epidemiology, zoonosis, china

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