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Cyclospora cayetanensis is a pathogenic agent originating from the intertropical zone. It causes diarrhoeal diseases in local populations as well as in travellers visiting these zones. In the first part of this work, an epidemiological study on drinking water supply (reservoirs and consumers' taps) was conducted in Hanoi over 12 months; samples were daily collected and have revealed the presence of Cyclospora cayetanensis oocysts during the whole year in tanks and only during monsoon season. Molecular methods were used for species identification. In the second part, we tried to investigate different water sources in Hanoi city in order to detect Cyclospora cayetanensis environmental contamination: groundwaters, surface waters collected in lakes and rivers and also waters from treatment plants. Our results show that none Cyclospora cayetanensis oocyst was found in the groundwaters and in the desinfected finished waters after treatment. In contrast, in rivers and lakes samples, the level of positivity reached about 63.6% with significant differences between the districts regarding the rates of oocysts recovery: only 24% positive specimens in Hoan Kiem district, whilst respectively 80.4%, 78.3% and 65% positive samples in Hai Ba Trung, Dong Da and Ba Dinh districts. The results of this study seem to confirm that environmental water is contaminated by Cyclospora cayetanensis oocysts and points out the importance of water as a significant source of human transmission. It is quite obvious that observation could be probably extended to the other endemic areas.

The diagnosis of microsporidiosis by staining stools is known to be fast and cheap. To obtain a specific and sensitive result, two colorimetric methods must be used: staining by the fluorochrome Uvitex 2 B (VAN GOOL) and trichrome. Among the four staining methods of trichrome currently studied, the WEBER coloration could be considered as the most efficient. The density of microsporidia spores could be semi-quantitatively evaluated, because their distribution is homogeneous.