Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
July 17, 2002
U of G Researchers Testing E. coli O157 Vaccine for Cattle
The risk of E. coli O157:H7 infections may soon be dramatically reduced, thanks to University of Guelph researchers who are assessing the benefits of a cattle vaccine for this bacterium.
There is consensus among researchers that reduction of E. coli O157:H7 in cattle is the key to minimizing the risk of infection in humans. Cattle are thought to be the primary source of the bacteria, which are found in the animals' intestines. It's estimated that 40 per cent of the 14 million cattle in Canada may be carriers of the bacterium. "It doesn't cause disease-the cattle are quite healthy-so we suspect that most cattle carry this organism at some stage," said pathobiology professor Carlton Gyles.
Cattle shed the bacteria in their feces, which then contaminate meat, produce and water sources. Some 1,500 human cases of E. coli O157:H7 illnesses are reported in Canada each year.
Gyles and Roger Johnson, head of the research section at Health Canada's laboratory in Guelph, are part of a Canadian Research Institute for Food Safety research team at the University of Guelph headed by population medicine professor Scott McEwen. They will be testing how well a vaccine developed by Bioniche Life Sciences Inc. eliminates the bacteria from cattle.
The food safety division of Bioniche Life Sciences, a Canadian biopharmaceutical company, develops veterinary products to improve the safety of food and water supplies worldwide.
Two preliminary studies comparing vaccinated and non-vaccinated cattle conducted by Bioniche showed a 90 per cent reduction of E. coli O157:H7 bacteria in the feces of the vaccinated cattle.
The vaccine stimulates production of antibodies to prevent E. coli O157:H7 from attaching to the intestinal wall of cattle. Because the antibodies limit colonization by the bacteria, replication and multiplication of the bacteria are impeded and the number of bacteria carried by the animal or shed into the environment is reduced.
Developing an effective vaccine is complex because cattle naturally carry E. coli O157:H7, said Gyles. "It is much more challenging to try to reduce or remove normal bacterial flora, compared with disease organisms," he said. "And I say that because normal flora represent bacteria that have developed mechanisms to live in peaceful coexistence with the host and so it's very hard to dislodge them."
Preliminary tests are still being done to ensure the vaccine is safe and has potency. The vaccine is administered subcutaneously into the cow's shoulder and does not appear to cause any side effects.
The researchers are in the process of gathering information on shedding of E. coli O157:H7 by cattle in cow/calf operations in Ontario. "This will allow us to better estimate how many animals need to be vaccinated and tested in order to determine the effectiveness of the vaccine," said Gyles. "Once that's through and everything is in place, we expect to be able to test the vaccine."
McEwen's team will test more than 100 herds in Ontario to compare the shedding of E. coli O157:H7 by vaccinated and non-vaccinated animals. "An important aspect of the study is that we won't know which animals have been vaccinated," said Gyles.
"Local farmers are eager to participate in the study because they are committed to safe and wholesome food," said McEwen.
Beginning this fall, they will perform over 130 tests from each farm, sampling manure, surrounding soil and surface water for traces of the bacteria. They will collect the samples five times over the course of a year, giving them evidence from some 65,000 tests.
If this vaccine in found to be effective against E. coli O157:H7, it could have profound benefits for people worldwide because it would significantly reduce the bacteria at the source, eliminating the chance of contaminating food or water, said Gyles. "It would have an impact on the direct transmission, when, say, meat is contaminated or when unpasteurized milk is contaminated or when children go to a petting zoo and pick up the organisms. It would also have an impact on indirect transmission when bacteria in cattle manure contaminate water that is used for irrigation or for washing fruits and vegetables which go to consumers."
The results of the University of Guelph researchers' study will complement other clinical trials being conducted by Bioniche in Western Canada for regulatory approval of the vaccine in Canada and the United States.
Martin Warmelink, president of Bioniche food safety, is optimistic about the results of the study. "We have a very high level of confidence that this will be developed into a product that will reduce the risk of contamination of hamburger meat-or meat in general-and of water sources," he said.
The E. coli vaccine is an all Canadian development project of the University of British Columbia, the Alberta Research Council, the Veterinary Infectious Disease Organization and Bioniche.
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