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News Article

Water trough levels may affect shedding of E. coli O157:H7

E. coli O157:H7 faecal shedding in feedlot cattle is common and is a public health concern due to the risk of foodborne transmission.

A study published in PLOS ONE suggests that water troughs on farms are a conduit for the spread of E. coli O157:H7 in cattle.

“Water troughs appeared in our mathematical model as a place where water can get contaminated and a potential place where we could break the cycle,” said Renata Ivanek, associate professor of epidemiology in the College of Veterinary Medicine at Cornell University and the paper’s senior author. The hypothesis was then tested in the field – with surprising results.

Cattle are the principal reservoir of E. coli O157:H7 for human infections. People commonly acquire infections from shiga toxin-producing E. coli through cow faeces-contaminated beef and salad greens.

“Farmers do not see a problem because there are no clinical signs in cows; it is totally invisible,” Ivanek said.

A vaccine to reduce bacterial shedding in cows exists, but the beef industry has little incentive to use it, partly due to cost, and the industry does not benefit from labelling beef as “E. coli safe,” Ivanek said. So Ivanek and a research team of 20 co-authors conducted a study to identify other ways to reduce the bacteria’s prevalence in cattle, which can vary over the year from zero to 100 percent of cows in a feedlot carrying the bacteria, with rates generally rising in the summer.

The researchers ran mathematical modelling studies to see if they could pinpoint areas in the farm where infections might spread between cattle. They found that water in a trough, especially in summer months, could heat and promote pathogen replication, causing more cows to acquire the bacteria when they drink. The researchers hypothesized that frequently changing the water in the summer could keep the water colder, limiting bacterial growth.

On most farms, water troughs automatically refill when they get low enough, and farmers can adjust the water levels so they refill more often. This tact saves water and keeps it fresher while ensuring cows still have enough to drink.

The group ran control trials in a feedlot over two summers. This involved reducing the water volume in troughs in randomly selected treatment pens and leaving the volume unchanged in control pens. They expected that reducing the water levels in troughs would prevent the spread of E. coli. Instead they found that it increased spread; in the treatment pens, the odds of finding shiga toxin-producing E. coli in cows was about 30 percent higher than in the control pens.

“Our modelling studies did pick up the right parts of the system,” Ivanek said, “but the mechanism that we postulated is the opposite from what we thought.”

More study is needed to determine why more water in troughs reduced E. coli in cows, but Ivanek questions whether the lower volume made it easier for cows to swallow debris at the bottom of tanks, or whether a fuller tank reduced E. coli concentrations.

The study will trigger more research on environmental sources of E. coli spread in cattle, Ivanek said.

Next steps include repeating the results in other feedlots, evaluating the effectiveness and cost benefit of using more water to reduce E. coli, investigating how seasons and temperatures play a role in prevalence of E. coli, and understanding the actual mechanisms that led to the results.

Wendy Beauvais, a postdoctoral researcher in Ivanek’s lab, is the paper’s first author. Co-authors included researchers from Texas A&M University, West Texas A&M University and Texas Tech University.

Read article: The prevalence of Escherichia coli O157:H7 fecal shedding in feedlot pens is affected by the water-to-cattle ratio: A randomized controlled trial by Wendy Beauvais, Elena V. Gart, Melissa Bean, Anthony Blanco, Jennifer Wilsey, Kallie McWhinney, Laura Bryan, Mary Krath, Ching-Yuan Yang, Diego Manriquez Alvarez, Sushil Paudyal, Kelsey Bryan, Samantha Stewart, Peter W. Cook, Glenn Lahodny Jr., Karina Baumgarten, Raju Gautam, Kendra Nightingale, Sara D. Lawhon, Pablo Pinedo and Renata Ivanek, published in PLOS ONE (2018) 13(2): e0192149, doi: 10.1371/journal.pone.0192149

Article details

  • Date
  • 06 March 2018
  • Source
  • Cornell University
  • Subject(s)
  • Food Animals