Giardia cyst and Cryptosporidium oocyst survival in water, soil, and cattle feces

Giardiasis and cryptosporidiosis are gastrointestinal diseases caused by protozoan parasites that mag infect domestic animals, wildlife and human beings. The ability of cysts and oocysts of these parasites to persist in the environment was determined because agricultural fecal waste has the potential to contaminate municipal water supplies. The degradation rate and viability of Giardia cysts and Cryptosporidium oocysts in water, cattle (Bos taurus) feces, and soil was evaluated at temperatures of -4, 4, and 25 degrees C for up to 12 wk. Cysts and oocysts were enumerated after staining samples with a specific fluorescent monoclonal antibody and the viability was determined using propidium iodide dye exclusion and mouse infectivity assays. Giardia cysts were noninfective in water, feces, and soil following 1 wk of freezing to -4 degrees C and within 2 wk at 25 degrees C. At 4 degrees C Giardia cysts were infective for 11 wk in water, 7 wk in soil, and 1 wk in cattle feces. Cryptosporidium oocysts were more environmentally resistant. At -4 and 4 degrees C, the oocysts could survive in water and soil for >12 wk but degradation was accelerated at 25 degrees C. Cryptosporidium oocysts also were degraded more rapidly in feces and in soil containing natural microorganisms. Contaminated cattle feces should be distributed on fields during warmer weather and after 12 wk of storage to reduce potential waterborne transmission following heavy runoffs.