Molecular characterisation and taxonomy of Cryptosporidium
Ryan, U.M. (2003) Molecular characterisation and taxonomy of Cryptosporidium. In: Thompson, R.C.A., Armson, A. and Ryan, U., (eds.) Cryptosporidium : from molecules to disease. Elsevier, Amsterdam, The Netherlands, pp. 147-160.
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Cryptosporidium is a coccidian parasite that is now a well-recognized cause of diarrhea in immunocompetent and immunocompromised humans and animals throughout the world (Fayer et al., 1997). In the most severely immunocompromised host, such as persons with AIDS, diarrhea caused by Cryptosporidium parvum infection of the gastrointestinal tract, becomes progressively worse with time and may he a major factor leading to death. While immunologically healthy patients usually recover spontaneously within 30 days, their clinical signs can be severe and their potential for transmission can be persistent for as long as 60 days after symptoms cease. At the present time there are no approved drug treatments for cryptospondiosis (cf. Fayer et al.. 1997, 2000).
Cryptosporidium has been identified as the cause of numerous waterborne, foodborne and daycare outbreaks of diarrheal disease worldwide (Fayer et al., 1997,2000). Water is increasingly recognized as an important vehicle for transmission of Cryptosporidium. The oocyst is the environmentally stable stage, which is able to survive and penetrate routine wastewater treatment. Cryptosporidium is also resistant to inactivation by chlorine at doses commonly used in drinking water treatment (Rose and Gerba. 1991). Currently, cryptosporidiosis represents the major public health concern of water utilities in developed nations (Thurman et al,. 1998).
Limitations associated with conventional diagnostic methods for cryptosporidiosis based on morphological features (Morgan and Thompson, 1998) have restricted our ability to clearly identify species. The application of sensitive molecular approaches, however, has resulted in the identification of new species of cryptosporidium and clearly indicates that the current species- level taxonomy of the genus does not reflect molecular phylogenetic analyses nor epidemiological data, and warrants reappraisal (Morgan et a.,. 1999a,b). Clearly a more thorough understanding of the taxonomy and how this relates to our understanding of the epidemiology and transmission dynamics of Cryptosporidium is required in order to adequately control outbreaks of the disease.
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|Murdoch Affiliation:||School of Veterinary and Biomedical Sciences|
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