Inactivation of Cryptosporidium parvum oocysts in field soil

Cryptosporidium parvum oocysts from dairy calves are believed to regularly contaminate watersheds. Identifying oocysts and measuring their viability in the natural environment are important elements in estimating the risk posed by this resistant organism. A 152 day field study was conducted to measure the viabilities of oocysts inoculated into 25 sampling points. Water potential, pH, and ammonium content were also measured at the same 25 sampling sites. A three-dimensional mapping program (Surfer) was used to create 3-D maps of the viabilities of C. parvum oocysts and other factors measured during the experiment. The results indicate that 3-D graphical presentation may be a useful means to identify potential sites of greatest risk of oocyst survival and could indicate areas where natural conditions are causing the most rapid oocyst inactivation, and this method can be a means for the future measurement of microorganism inactivation in the natural environment.