What is the primary concern regarding E.coli O157H7 in cattle?

The primary concern regarding E. coli O157:H7 in cattle centers on the risk for zoonotic transmission. This particular strain of E. coli is not only harmful to cattle but poses significant health risks to humans who may come into contact with infected animals or consume contaminated products. Cattle can carry the bacteria without showing signs of illness, thus acting as a reservoir for zoonotic transmission when fecal contamination occurs in environments such as farms or processing facilities.

Understanding this risk is crucial in controlling outbreaks and preventing public health issues associated with foodborne illnesses. While high mortality, antibiotic resistance, and the presence of parasites are relevant considerations in veterinary and zoonotic health, they do not capture the immediate and direct concern of E. coli O157:H7's ability to infect humans, making zoonotic transmission the primary focus in this context.