Cattle can be naturally colonized with foodborne pathogenic bacteria such as Shiga Toxin-producing E. coli (STEC) in their gastrointestinal tract. While these foodborne pathogens are a threat to food safety, they also cause human illnesses via cross contamination of other foods and the water supply, as well as via direct animal contact.
Callaway et al. 2013. Agric. Food Anal. Bacteriol. 3:39-69.