Strategies for detecting pathogenic protists in water: the point on Cryptosporidium

Parasitic infections having a well known impact in tropical pathology play also a role in the opportunistic pathology area, which affects in a same way developed and developing countries. The growing number of severely immunocompromised individuals - as a result of AIDS pandemic, cancer chemotherapy, and organ transplantations - has entailed the increasing prevalence of emerging parasitic infections. This increase in the number of individuals exposed to parasitic infection has made essential an accurate assessment of these infectious risks. The detection of pathogen protists in the environment is therefore becoming a crucial problematic that concerns as well protists as other parasites of oro-fecal transmission. In this paper, we present an overview of the different strategies to detect protists in water by focusing on the conventional and more novel techniques that are currently available for Cryptosporidium. Concentration, purification, and detection, that are the three key steps in ail methods that have been approved in standard protocols, are here considered separately with advantages and drawbacks presented for each. Monoclonal antibodies specific to Cryptosporidium have significantly improved the purification and the detection of ooeysts in water concentrates. However, the limiting factor for most protozoa (except Giardia) remains the lack of commercially available antibodies to perform these two steps. To date conventional and new PCR-based detection methods allow to identify or/and quantify the species and genotypes of Cryptosporidium sp. As there is great interest in determining whether Cryptosporidium ooeysts recovered from the environment are still alive and infectious, viability and infectivity parameters been also considered here. Cell culture techniques can be used to examine oocyst infectivity. With the availability of numerous target markers, RT PCR should also likely emerge as an important method to assess oocyst viability