TUESDAY, Sept. 17 (HealthDay News) -- Vaccinating cattle against
E. colibacteria could cut the number of human infections by
85 percent, far higher than previous estimates, British scientists
The researchers reviewed the way that
E. coliis transmitted from cattle to humans, noting that the
risk of infection is particularly significant during the brief
periods when cattle are "super-shedding" extremely large amounts of
the bacteria in their feces.
"As far as we can assess, the major risk to humans is from those animals that are shedding the bug heavily," said Stuart Reid, senior study author and a principal at the Royal Veterinary College at the University of London. "If the vaccine has an impact on these animals at that time, the risk to humans is disproportionately reduced."
Previous research has predicted that vaccination of cattle could
E. colirisk by 50 percent, but those studies did not take
into account the effect of vaccination on "super-shedding," the
The new study of Scottish cattle appeared in the Sept. 16-20
issue of the journal
Proceedings of the National Academy of Sciences.
E. coliinfection causes severe gastrointestinal illness in
humans, in some cases leading to death. It is spread by consuming
contaminated food or water, most often ground beef.
Nearly 1,100 confirmed cases of
E. coliinfection occurred in the United States in 2012,
according to the U.S. Centers for Disease Control and Prevention.
They led to 275 hospitalizations and two deaths. The CDC said that
for every reported case of
E. coli, there are probably 26 more that go undiagnosed.
E. colihave been approved for cattle in the United States
and Canada, but farmers have not shown much interest in using them,
the study authors said.
Farmers aren't vaccinating cattle against
E. colibecause cattle don't get sick from the bacteria, said
Mike Doyle, a distinguished professor of food microbiology and
director of the Center for Food Safety at the University of
"The farmer doesn't get any bang for the buck from a production perspective," Doyle said. "The vaccine doesn't help the animal grow more healthy."
Government intervention likely would be required for widespread
vaccination to occur. "Unless all farmers were required to
vaccinate by the government, it wouldn't be cost effective or cost
competitive for them to do that," Doyle said.
Such intervention should be seriously considered, said lead
study author Dr. Louise Matthews, a senior research fellow in the
Institute of Biodiversity, Animal Health and Comparative Medicine
at the University of Glasgow.
"Treating cattle in order to reduce the number of human cases [of E. Coli] certainly makes sense from a human health perspective, and, while more work is needed to calculate the cost of a vaccination program, the public health justification must be taken seriously," Matthews said.
The researchers started their work first by identifying the
genetic marker associated with
E. colisuper-shedding in cattle. They then studied the
relationship between cattle predisposed to super-shed
E. coliand human outbreaks of the illness, concluding that
the types of
E. colilinked to super-shedding cause the vast majority of
The researchers now are working to develop even more effective
vaccines that would further reduce the risk of
Doyle warned against generalizing the Scottish results to the
United States, however, noting that farming methods are very
different between the two. For example, Scottish beef is mostly
"You can't automatically extrapolate what they find over there to what we have here," he said. "There's probably more research that would need to be done to see how useful or relevant this information is to American farmers."
Dr. Georges Benjamin, executive director of the American Public
Health Association, said the results are intriguing. He said,
however, that he's concerned that a vaccine might reduce emphasis
on the common-sense food-safety methods that now provide effective
protection against foodborne illness.
"I do want to emphasize [that] it does not replace careful monitoring of animal health and surveillance of the food-safety process as animals move through the pipeline to become our food," Benjamin said. "It also doesn't replace good food safety. You're still going to have to wash your hands. You're still going to have to make sure your food is prepared properly."
For more about foodborne pathogens, visit the
U.S. Centers for Disease Control and
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