Effect of various environmental factors on the viability of Cryptosporidium parvum oocysts
To evaluate individual and combined effects of temperature (4, 18 and 25°C), pH (7 and 10), ammonia (5 and 50 mg l−1) and exposure time (1, 2, 4 and 6 days) on the viability of Cryptosporidium parvum oocysts in water. Methods and Results:
The viability of oocysts was evaluated using the fluorogenic vital dyes assay (4′,6-diamidino-2-phenylindole and propidium iodide). All the factors analysed (temperature, pH, ammonia and exposure time) and their interaction were statistically significant (P < 0·005). Exposure of oocysts to pH 10 for 6 days at 25°C reduced oocyst viability from ∼80% to 51%. Similarly, the exposure of C. parvum oocysts to 5 mg NH3 l−1 and 50 mg NH3 l−1 for 4 days reduced their viability from between ∼80% to 41·5% and 14·8%, respectively. Conclusions:
The interaction between pH, temperature and exposure time may have adverse effects on the survival of C. parvum oocysts in water. Low concentrations of ammonia, as commonly found in alga-based wastewater systems, over a long period of time can produce high C. parvum oocyst inactivation rates. Significance and Impact of the Study:
This study provides relevant data on the inactivation of C. parvum oocysts in alga-based wastewater-treatment systems in the northwest of Spain.
Document Type: Research Article
Affiliations: 1: Department of Ecology, Faculty of Biological and Environmental Sciences, University of León, León, Spain 2: Scottish Parasite Diagnostic Laboratory, Stobhill Hospital, Glasgow, Scotland, United Kingdom
Publication date: 01 April 2008