Which of the following are potential sources of E. coli O157 contamination on cattle farms?

• A. Contaminated feed only
• B. Contaminated water troughs only
• C. Contaminated feed and contaminated water troughs
• D. Neither feed nor water are sources

Answer: (C)

E. coli O157:H7 can be shed in cattle feces and contaminate the farm environment through multiple routes. Feed can become contaminated if it contacts manure or is stored where fecal material can reach it, allowing the bacteria to be ingested by cattle or people handling the feed. Water troughs can also be sources because contaminated runoff, wildlife, or dirty water supplies can introduce the bacteria into the troughs, and cattle drink from them, facilitating exposure. Because both feed and water troughs can harbor and transmit the organism, recognizing that multiple inputs contribute to contamination is essential for prevention. In practice, this means ensuring clean water sources, proper trough sanitation, and feed handling practices to minimize fecal contamination.