Role of livestock in microbiological contamination of water: Commonly the blame, but not always the source

Since the 1940s, livestock production practices in North America have evolved from extensive to intensive systems, concentrating animals, nutrients, and their associated microorganisms within limited geographical areas. Livestock wastes can harbor both bacterial and protozoal pathogens, and surface and groundwater contamination has been, but is not always, linked to extensive and intensive livestock operations. In mixed-activity watersheds, fecal contamination can be of livestock, human, or wildlife origin. Fecal indicator microorganisms are not always indicative of the disease risk of water, a limitation that is being overcome by the development of molecular identification methods that specifically target pathogens. Best management manure handling, storage, and application practices can substantially reduce the risk of microbial contamination of surface and groundwater. Livestock management practices can reduce the release of pathogens into the environment. The purity of water can never be fully guaranteed; consequently, a multiple-barrier approach is most efficacious in ensuring the production of pathogen-free drinking water.