Protecting watersheds from Cryptosporidium in manure: a literature review

摘要

Tconcept of watershed protection finds regulatory expression in the US Environmental Protection Agency's (USEPA's) surface water "Fil-tration Avoidance Determination" program currently applicable to about 90 utilities. The largest utility that has been granted a filtration avoidance waiver is that of New York City. By operating under a USEPA waiver, the utility avoids constructing filtration facilities at a capital cost exceeding $2 billion. The full version of this article is available online at www.awwa.org/ communications/journal/2004/february. A major consideration in granting a filtration waiver is whether a watershed is adequately protected against the introduction of Cryptosporidium parvum, the causative agent of cryptosporidiosis disease in humans. The oocyst stage of this proto/oan is of special significance because it encloses and protects the infective sporozoite stage; thus, it is the transmissive agent of the disease. Oocysts are shed in large numbers by "scouring" (overt diarrhea) neonatal calves, and the oocysts are highly resistant to chlorination. In addition to monitoring raw surface waters and removing oocysts through treatment at facilities, developing and taking measures to inactivate oocysts at their sources, such as in cattle manure before it is spread on fields, are indicated. There are approximately 250 dairy farms in the watersheds of New York City.