Multistate Study to Determine the Presence of Salmonella spp. in Farm Animals and their Environment

Salmonella is the second most common cause of foodborne infection in the Unites States (US). It is estimated that about 1.4 million people suffer from salmonellosis a year in the US with an estimated annual cost of $2.9 billion. Human cases of salmonellosis are often related to the consumption of raw meat and unpasteurized milk and milk products. Whereas the fecal-oral contamination is well established at farm level, less in known about the role of the environment on the Salmonella survival. The objective of this study was to compare isolation of Salmonella in farm animals and their environment based on spatial, temporal, and environmental factors to provide population-based epidemiological information that can be used in assessing risk and development risk management strategies. Samples were collected from 12 different locations in 5 states (Tennessee, Alabama, North Carolina, California and Washington). Samples originated from dairy cows, beef cattle and swine herds. Environmental samples (n=360) and rectal swabs (n=1200) were analyzed using BAM modified protocols. Salmonella positives were characterized with Riboprinter® and Pulsed-Field Gel Electrophoresis using PvuII and XbaI restriction enzymes. Salmonella was most frequently isolated from swine, the animals being the major reservoir, with an isolation of fecal materials of 11.9%, followed by rectal swabs (8.8%) and feed (7.7%). For dairy cows and beef cattle, the major reservoir of Salmonella was the environment, especially the feed (3.1%), followed by soil samples (2.0%). The most common serotypes isolated from swine were S. Anatum, S. Javiana, S. Newington, and S. Worthington. The most common serotypes found in dairy cows were S. Anatum, S. Newington and S. Javiana, whereas only two serotypes were isolated from beef cattle, S. Anatum and S. Newington. The Simpson’s diversity index was calculated for Riboprinter (0.86) and PFGE (0.98). This data indicates significant diversity among the Salmonella isolated, but we were able to find regional and spatial differences among the Salmonella isolates. Breaking the contamination cycle between the animals, their environment, and management practices to control swine fecal materials will be essential to reduce the isolation of Salmonella in farm animals.