Author of Response: Chip Simmons, Ph.D., Assistant Research Professor at the University of North Carolina Chapel Hill School of Public Health osimmons@email.unc.edu Response: This is a difficult question because of the lack of specific epidemiological studies to address this issue. Farmers and farm workers that work with livestock are a unique group with the potential for occupational exposure to animal fecal wastes. Because of this, they are at greater risk than the general public for exposure to pathogens contained within this waste material. Farm workers do get sick from occupational exposures to microbial contaminants – this is especially true for respiratory infections associated with bacterial endotoxins in animal housing facilities. Many times, as with the general population, illnesses go unreported to the medical community, leading to a significant underestimate of the true levels of worker related illnesses. It is unknown if this underreporting of illness is higher within this group than in the general population. Microbial risks to farm workers that work with livestock are generally associated with animal manure and can be reduced by proper handling and management of fecal waste material. Exposures to pathogens that may be present in animal wastes may come from a variety of routes, including direct exposure, contaminated water (surface or ground), air, and vectors, such as houseflies and rodents. The potential for illness depends upon both the pathogen and individual. Because of this, there are characteristics associated with each that can influence the severity of the disease and ultimate health outcome. Important pathogen factors include virulence properties of the organisms, environmental factors that may adversely affect the survival rate of the pathogen, such as temperature, UV exposure, humidity, and class of pathogen. Certain bacteria and parasites form environmentally stable and resistant forms, called spores and cysts or oocysts, respectively. Host factors that can influence the pathogen-host interaction are age, immune status, diet and nutrition, pregnancy, and dose of pathogen. Additional Reading: Cole D., L. Todd, and S. Wing. 2000. Concentrated Swine Feeding Operations and Public Health: A Review of Occupational and Community Health Effects. Environmental Health Perspectives Vol. 108(8): 685 – 699. Donham KJ. 2000. The Concentration of Swine Production. Effects on Swine Health, Productivity, Human Health, and the Environment. The Veterinary Clinics of North America. Food Animal Practice. Vol. 16(3): 559 – 597. Eduard, W., J. Douwes, R. Mehl, D. Heederik, and E. Melbostad. 2001. Short Term Exposure to Airborne Microbial Agents During Farm Work: Exposure-Response Relations with Eye and Respiratory Symptoms. Occupational and Environmental Medicine. Vol. 58(2): 113 – 118. Strachan, N.J.C., D.R. Fenlon, and I.D. Ogden. 2001. Modeling the Vector Pathway and Infection of Humans in an Environmental Outbreak of Escherichia coli O157. FEMS Microbiology Letters. Vol. 203(1): 69 – 73.

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