Cryptosporidium is a pathogenic parasite that is commonly found in lakes and rivers, particularly those contaminated by sewage and animal wastes. The parasite exists as an oocyst, an egg-shell-like covering that protects the microorganism from such hazards chlorine, a disinfectant. 

 

Unfortunately, the Cryptosporidium oocyst is invisible to the naked eye. Only recently have tests been developed to detect it in drinking water.

 

Of all the Cryptosporidium species, EPA believes that only the species Cryptosporidium parvum causes cryptosporidiosis in humans. But not all oocysts present in water are in the infectious stage.

 

How does it get into drinking water?

 

Cryptosporidium is typically found in surface water bodies, like lakes, rivers, and streams. It is found in human and animal fecal matter, so water bodies that are contaminated with sewage or animal waste likely contain Cryptosporidium. For this reason, water sources near farms are particularly vulnerable to Cryptosporidium contamination.

 

Shallow aquifers that are recharged by surface water may also be susceptible to Cryptosporidium contamination. But generally, only surface water sources are affected by the oocyst.

 

Don’t water treatment plants eliminate it?

 

Current EPA drinking water standards were not designed to ensure the removal or disinfection of Cryptosporidium. In fact, the current national primary drinking water standards do not contain a regulation for Cryptosporidium. More importantly, the protective oocyst prevents most water treatment plants from killing the microorganism with chlorine, the disinfectant most commonly used to control microbial pathogens. To effectively control Cryptosporidium, the oocysts must be physically removed from drinking water by microfiltration. This is not economically feasible for municipal water treatment facilities.