The trend in animal production has shown a dramatic shift in the last 50-60 years from small family farms and grazing operations towards large commercial confinement operations. Since 1982, animal production at these facilities has nearly doubled while at the same time they have become more spatially concentrated. Recently, the U.S. Department of Agriculture (USDA) reported that more than 80% of all livestock revenues are generated in confinement facilities that account for a scant 18% of all livestock operations. In fact, more than 43% of all beef cattle, dairy cattle, swine, and poultry are raised in the largest two percent of operations. The concentration of animals into confinement facilities poses many environmental challenges, among which pathogenic microorganisms of fecal origin are of concern. In this report, we synthesize the current state of knowledge regarding pathogen research as it relates to livestock confined animal feeding operations (CAFOs), including a summary of research ongoing at USDA and other federal agencies. Pathways for the release of zoonotic agents and antimicrobial-resistant bacteria endemic in animals raised in confinement and their potential to persist in different milieus are reviewed. We discuss the impact to the environment and public health and welfare posed by the release of these agents from CAFOs, as well as manure management practices that are employed to mitigate their release into the environment. The objectives of this review are to summarize pathogen issues with regard to livestock CAFOs and identify and discuss gaps in the research that need to be addressed to improve public health.

"EPA/600/R-06/021." Includes bibliographical references (p. 99-175). "September 2005."