A Systems-Based Risk Assessment Model for Animal and Plant Production

NON-TECHNICAL SUMMARY: This research will permit science-based decisions to be made and effectively communicated to a diverse clientele on risk/cost analysis of management options, exposure and carriage of pathogens by animals, development of a conceptual site model, estimation of human exposure and human health risk and the significance of geographic and climatic factors on management of pathogens in the production environment.

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APPROACH: A detailed and comprehensive epidemiological characterization of four foodborne pathogens and two protozoans in soil, air, water, humans and animals located within three specific types of animal production settings in four geographic regions (California, Tennessee, Alabama and Washington) over a 24-month period will be completed. This information will be used to develop a risk-based systems approach for enhanced understanding of the epidemiology, transmission and persistence of foodborne pathogens and parasites in the rural and farm environment to develop a spatial model using Geographical Information Systems to identify risk factors for contamination of humans and animals with pathogens from the environment.

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PROGRESS: 2001/09 TO 2005/09<BR>
The objective of this study was to determine incidence and gather epidemiological information to determine occurrence of Escherichia coli O157:H7, Listeria monocytogenes (LM) and Salmonella in cattle, swine and poultry and the farm environment. Environmental samples (n=648) and fecal swab samples (n=328) from 16 farm locations in the U.S. were collected over 16 months for each of the enteric microorganism and LM. Overall, in fecal swabs E. coli O157:H7 was positive (latex agglutination confirmed) in 6% of beef cattle (n = 328), 5% of dairy cattle (n=328), 9% of swine (n=326), 5% of turkey (n=80) and 1% of chickens (n= 224). E. coli O157:H7 was isolated infrequently from environmental samples (1-3%). E. coli O157:H7 was isolated from feed samples (up to 3 samples) from the states of Tennessee and Washington. Since E. coli O157:H7 were seldom isolated from feeds or bedding, sampling for E. coli O:157 at the farm should focus on the feces or fecal swabs for optimal recovery. The incidence of E. coli O:157 in swine and turkey was surprisingly high which indicates that swine and poultry may serve as vectors for foodborne outbreaks of E. coli O:157. LM was isolated from 8.25% of all samples. Swine farms exhibited the highest number of LM isolates (27), followed by dairy cattle farms (26), poultry farms (24) and beef cattle farms (18). The Spring sampling exhibited the highest number of LM isolates (37), followed by Winter (31), Summer (11) and Fall (8). Salmonella was recovered in 16% of the dairy cow samples, and 15% of poultry samples. Salmonella isolation was higher in the dairy environment (20% bedding, and 15% soil and feed) than from fecal swabs (10%). In poultry, the incidence of Salmonella in fecal swabs was low but for environmental samples was: 31% from feed, 23% from litter, and 15% from soil around the facilities. There was low correlation between Salmonella in fecal swabs and environmental samples in dairy cows, chickens and turkeys. Although fecal swabs in swine gave good recovery of Salmonella, fecal swabs from dairy cows and poultry are not a good method for determining presence of Salmonella in the facility. To determine the prevalence of Salmonella in dairy cattle, combining soil-bedding or feed-bedding sampling gave the highest prevalence (30%) of Salmonella. For poultry, the combinations feed-litter or feed-soil sampling gave highest recovery for Salmonella (38%). Both sample type and modification of BAM or USDA methodology significantly (p<0.001) affected recovery of pathogens at the farm.
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IMPACT: 2001/09 TO 2005/09<BR>
The incidence of E. coli O157:H7 in swine and turkey was significantly higher than the incidence in beef cattle or dairy cows. Therefore swine and poultry may serve as previously unidentified vectors for foodborne outbreaks of E. coli O157:H7 since the foods associated with many outbreaks are unidentified. Both poultry and pork products should be investigated further to determine the risks associated with Shiga toxin producing E. coli and these foods. In addition, questions concerning consumption of pork and poultry should be included with questions about ground beef on epidemiological questionnaires for victims of foodborne illness caused by E. coli O157:H7.