Cattle vaccine developed for strain of E. coli

Canadian scientists have developed a cattle vaccine against the dangerous E. coli strain that has wreaked havoc with fresh produce this year, first in an outbreak involving spinach, and then another with contaminated lettuce at a string of Taco Bells in New York and elsewhere.

The vaccine, which targets Escherichia coli O157:H7, has been granted preliminary approval by the Canadian Food Inspection Agency. The U.S. Department of Agriculture also is studying the vaccine, which targets a unique protein in the virulent strain. The inoculation is manufactured by Bioniche Life Sciences Inc., in Ontario, which this week reported that the vaccine had received a conditional license.

Work on the vaccine first began in the 1990s by a University of British Columbia scientist who discovered E. coli O157:H7’s unique production of “pedestal proteins” that allow it to attach to intestinal cells. Vaccination causes cattle to produce antibodies against pedestal proteins, thwarting the microbe’s ability to create robust colonies in a cow’s gut.

But although the vaccine promises to reduce the presence of the bacteria in cattle, the pathogen still can be carried by wild animals or enter the environment through contaminated groundwater that can remain tainted for long periods, said Dr. Patricia Dillon of the Suffolk Health Department on Long Island, who is leading investigations into E. coli contamination.

Bioniche president Graeme McRae said the vaccine was difficult to develop because E. coli O157:H7 does not cause disease in cattle, and the inoculation had to be designed in such a way that strains of the bacterium that are essential to bovine digestion were not eliminated.

“If it’s used, it will make a huge difference,” McRae said. So far, he said, the vaccine has been administered successfully to 30,000 cattle in Canada and the United States in field trials.

A final round of study is under way, and full Canadian licensure is expected next year.

David Smith, an associate professor of veterinary medicine at the University of Nebraska, Lincoln, who has led much of the vaccine’s work in the United States, said the inoculation has the remarkable ability to reduce the pathogen in cattle by up to 70 percent. This brings the year-round level of E. coli O157:H7 in herds to those normally seen in winter when the bacteria are less prevalent. Human infections, as a result, are nonexistent in winter.