2003 Volume 77 Issue 2 Pages 75-82
Cryptosporidium parvum oocysts were exposed to the mixed-oxidant solution, which was electrochemically generated by Miox Water Disinfection Unit, and sodium hypochlorite in phosphate buffered saline (PBS, pH 7.2) or biologically treated wastewater at 25°C by using concentrations of residual chlorine of up to 5 mg/l and contact times of up to 8 h. The effect of two disinfectants on infectivity of the oocysts in a neonatal murine model was comparatively evaluated by determining the total number of oocysts recovered from the intestine. Exposure to the mixed-oxidant solution at 2 and 5 mg/l (residual chlorine) yielded a significant inactivation of infectivity in the dose-and exposure timedependent manner, while exposure to 5 mg/l (residual chlorine) of sodium hypochlorite for contact times of up to 4 h produced no measurable inactivation of infectivity. Morphological examination also revealed a picture of degenerating oocysts after exposure to 5 mg/l (residual chlorine) of the mixedoxidant solution, but not with sodium hypochlorite. When the oocysts were exposed to either biologically treated wastewater-or PBS-diluted the mixed-oxidant solution at 5 mg/l (residual chlorine) for4 h, the disinfectants produced a significant inactivation of infectious oocysts. The decrease number of the oocysts was 0.8 log10 in the former and 2.1 log10 in the latter. These results demonstrate that the mixed-oxidant solution may be a useful disinfectant against Cryptosporidium oocysts, but appropriate applications need to be validated.
