The potentially deadly E. coli strain 0157:H7 makes headlines so often these days that finding it in feedlot cattle would seem simple.

Not so, said Dave Smith, a University of Nebraska veterinary scientist.

"It's very rare to find 0157:H7 in an animal," Smith said. That rare event can produce huge problems. In November 1998, the IBP beef processing plant in Dakota City recalled more than half a million pounds of ground beef after a sample showed signs of 0157:H7 contamination. Similar recalls involving millions of pounds of ground beef in 1997 spurred the state Legislature to pass LB1206, which appropriated $250,000 annually for five years to NU for E. coli 0157:H7 research.

Not only is 0157:H7 rarely found in an individual animal, it doesn't make them sick. Researchers must rely on diagnostic tests of individual cattle to determine its presence - a prohibitively expensive process.

"We want to develop an efficient way to find 0157:H7 by sampling whole pens of animals, rather than individual animals," Smith said.

Smith and colleagues from NU's departments of animal science and veterinary and biomedical sciences and the Great Plains Veterinary Educational Center ultimately want to identify feedlot management practices that will further reduce the number of cattle carrying the organism when they leave the feedlot.

To study the bacteria and how it passes among cattle in feedlots, scientists first must find an animal carrying 0157:H7 and shedding it in its feces. After developing a method, or protocol, for testing animals, researchers tried it in feedlot conditions.

Every three weeks last summer, Animal Scientists Terry Klopfenstein and Todd Milton sampled the feces of 96 cattle in 12 pens at NU's Agricultural Research and Development Center near Mead. They sent samples to Veterinary Scientist Rod Moxley at NU's Veterinary Diagnostic Center to be cultured and examined for 0157:H7.

The bacterium truly is rare. The Institute of Agriculture and Natural Resources team found only one animal shedding 0157:H7; it tested negative three weeks later. The results weren't that surprising, Smith said, and illustrate the difficulties of field research on 0157:H7.

"We need a more sensitive test for sampling cattle that also will be efficient and cost-effective. We're making modifications on existing tests now," Moxley said.

The new tests will be tried on infected cattle in laboratory conditions before field testing this spring, Smith said. Testing will include private feedlots to provide a more realistic sample.

In another study, the team tested ways of decreasing bacteria levels in water tanks. "0157:H7 may be transmitted through water and feed," Smith said. "If it is, disinfecting water troughs could be a way of breaking the transmission cycle." Using coliform bacteria, which acts similarly to E. coli, researchers cleaned water tanks with three different methods.

Disinfecting troughs with a bleach solution after scrubbing was the only method that significantly reduced bacterial levels, but only temporarily. Within 24 hours bacteria built up to pre-disinfection levels, showing that disinfection alone won't control E. coli, Smith said. They'll conduct similar studies on feed contamination this spring.

These studies are only the first in a wide-ranging research effort to learn about E. coli 0157:H7.

"This first year our objective was just to get our hands dirty and establish some basic protocols," Smith said. "Eventually we hope to develop management strategies that can reduce the presence of E. coli in feedlots so we won't have cattle walking into packing plants carrying the bacteria."

This research is funded by LB1206 and the Nebraska Beef Council.

- Monica Manton Norby

Veterinary Scientist Dave Smith collects feedlot water tank samples at NU's Agricultural Research and Development Center near Mead.