In the United States, foodborne outbreaks of Escherichia coli O157:H7 illness have often been linked to the consumption of contaminated, undercooked ground beef. However, the occurrence of E. coli O157:H7 has also been reported in other farm animals. The objective of this study was to evaluate the occurrence of E. coli O157:H7 on diverse farm types and from a variety of farm samples. Rectal swabs (n=1686) and environmental samples (n=576) were collected from 16 farms in five states over 24 months and analyzed for the presence of E. coli O157:H7. Overall, E. coli O157:H7 was found in 3.6% of beef cattle, 3.4% of dairy cattle, 0.9% of chicken, 7.5% of turkey, and 8.9% of swine samples. The pathogen was isolated sporadically from each of the environmental sample types. Of particular concern was the isolation of E. coli O157:H7 from fresh feed samples, indicating a potential vector for transmission. The data from this study indicate a high occurrence of E. coli O157:H7 on swine and turkey farms. This unexpected result suggests that more research on the occurrence of E. coli O157:H7 on these types of farms is required in order to better understand potential reservoirs of pathogenic E. coli.
The occurrence patterns and molecular characteristics of Salmonella are important for surveillance and control of the pathogens. Objectives of this study were to determine month-to-month variation and seasonal effects on the occurrence of Salmonella in dairy animals and environments and to characterize selected Salmonella isolates. A total of 7680 animal and environmental samples, collected monthly from a dairy farm, were analyzed for the presence of Salmonella during a 12-month study. Major sources of Salmonella on the dairy farm (% positive) were milking parlor air (62%) and bird droppings (63%) during winter; feeds (50-58%), water (53-67%), calf bedding (63%), soils (60-63%), milking parlor air (60%), and bird droppings (50%) in spring; all animal and environmental samples (40-92%) except milking parlor air (25%) and bulk tank milk (29%) in summer; and feeds (60-71%), cow beddings (59%), cow soils (50%), air (46-71%), and insects (63%) during fall. Salmonella ribotyping indicated that most serovars came from different sources but some might have originated from a common source and transmitted from site to site on the farm. These data provide some important information on key animal and environmental sampling sites needed to initiate on-farm management programs for control of this important foodborne pathogen.
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