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Is There a Way to Keep E. coli Out of Romaine Lettuce?

By December 7, 2018December 10th, 2018No Comments

Somewhere in Canada, 24 people have gone through a frightening experience caused by the simple act of eating romaine lettuce.

It happened sometime in late October or early November, when they unknowingly ingested a dangerous pathogen — E. coli O157:H7 — hiding in the lettuce leaves.

Days later they began to feel symptoms, possibly a headache or a mild fever. They could have developed nausea, abdominal cramps and bloody diarrhea. They would have been so distressed that they went to their doctor or an emergency room.

Eight were sick enough to be hospitalized even though there’s not much doctors could do, except monitor them and keep them hydrated. Antibiotics are never used when doctors detect E. coli O157 because that can make the symptoms worse.

If the E.coli infection is serious enough, it can cause kidney failure. And that happened to one person, who may have needed dialysis, possibly for life.

‘Lightning strikes twice’

At almost the same time last year, 48 Canadians in Ontario, Quebec and Atlantic Canada had similarly distressing experiences after eating romaine lettuce and becoming infected with the identical strain of E. coli.

Seventeen people ended up in hospital and one Canadian died.

Last February, the Public Health Agency of Canada quietly closed the file without knowing where the lettuce came from or how it became infected.

There’s no way that, as far as I’m concerned, somebody should get sick for doing something that is not dangerous.– Lawrence Goodridge, McGill University 

The offending bacteria lurked all winter somewhere in the coastal fields of central California only to strike again in October making at least 63 people sick in Canada and the U.S. and prompting a North America-wide alert to avoid romaine lettuce.

For every person who is diagnosed with E. coli O157, the Public Health Agency of Canada estimates another 20 were probably infected but never diagnosed.

This time investigators have an important clue — a DNA fingerprint match linking the two outbreaks.

“To actually get the same strain, associated with the same produce, at the same time of year, when you say lightning strikes twice, that’s exactly what it is,” said Keith Warriner, a food science professor at the University of Guelph.

“It’s pretty good evidence it’s the same source. The question is what is that source?” said Lawrence Goodridge, a food safety scientist at McGill University.

A leading hypothesis is that animals, probably cattle, were the original source of the E. coli.

And the mode of infection has a high probability of being irrigation water contaminated by cattle feces.

‘We’re getting so many outbreaks now’

It’s estimated about 250 Canadians are infected with a dangerous Shiga toxin producing E. coli every year, after eating food that should be safe and healthy. Around eight people die.

“There’s no way that, as far as I’m concerned, somebody should get sick for doing something that is not dangerous,” said Goodridge. “It’s both nothing to panic about but at the same time it’s something we have to urgently work on.”

Scientists first discovered this dangerous strain of E. coli in 1982 and since then it has caused a series of high-profile outbreaks in beef, lettuce, spinach and other fresh produce across North America.

“It gets serious when we’re getting so many outbreaks now,” said Warriner.

But after three decades, there is still no consensus about what should be done to prevent human exposure.

Relying on testing food for E. coli is impractical, experts say.

“For practical purposes right now it’s difficult to test all foods rigorously because even small amounts of contamination can cause serious illness,” said Herb Schellhorn, a biology professor who researches E. coli at McMaster University.

“It’s needles in haystacks,” said Warriner.

Improving the ability to trace food back to the growing area through better labelling is only useful after someone has already become ill.

“We can identify which lettuce made you sick. But it’s not going to stop you getting sick.” – Keith Warriner, University of Guelph 

“I’m a little concerned with the focus on traceability in that it’s kind of like putting a Band-Aid on the situation because if you solve the problem you won’t need to trace the food back,” said Goodridge.

“We can identify which lettuce made you sick. But it’s not going to stop you getting sick,” said Warriner.

Scientists are studying ways to kill E. coli in irrigation water and in harvested crops through sterilization, irradiation or bio-pesticides.

Made-in-Canada vaccine not being used

But what about tackling E. coli at its primary source, in the intestines of livestock?

That’s what University of British Columbia scientist Brett Finlay was trying to do when he developed a made-in-Canada vaccine for cattle that would reduce the amount of E. coli they shed into the environment.

Years ago Finlay discovered how the bacteria bind to intestinal cells.

Based on that discovery, he worked with a colleague at the University of Saskatchewan to design the vaccine.

With support from Canada’s research foundations and about $25 million in public funding from the federal and provincial governments, a small Canadian company called Bioniche turned Finlay’s discovery into a world first.

The vaccine was tested in series of studies showing it was safe, and that it did not harm the animals.

A team of  independent Scottish researchers developed a computer model and calculated that vaccinating cattle could reduce human infections by up to 85 per cent.

It almost killed me. It was very sad. The whole thing was very sad.– Graeme McRae, former president of Bioniche

The vaccine was approved by the Canadian Food Inspection Agency in 2008. But Canadian cattle producers were not persuaded. And the vaccine went out of production.

“The whole thing became very political,” said Graeme McRae, former president of Bioniche. The company is no longer in business. “It almost killed me. It was very sad. The whole thing was very sad.”

One problem: cattle producers were reluctant to pay for the vaccine because it didn’t improve the health of their animals and added no value to their operations.

And the federal government didn’t offer to pick up the estimated $50 million annual cost even though the vaccine might reduce the risk of human E. coli infection.

“It’s a bit ironic. Because of the creativity of the idea to vaccine the cows for a human disease, it sort of landed in a never-never land for who is going to take onus for it and [be] responsible for it,” said Finlay.

Cattle producers still have doubts

Today the vaccine manufacturing plant in Bellville, Ont., sits idle. And the original patents have been returned to UBC where they’re sitting in a filing cabinet somewhere, available to anyone who might want to revive the idea.

“It’s very disappointing to do the work and find something that should make a difference, and probably would make a difference,” said Rodney Moxley, professor of veterinary medicine and biomedical sciences at the University of Nebraska. He published nine peer-reviewed papers showing the vaccine worked after testing it in more than 20,000 animals.

“If they could just simply solve the questions about who’s going to pay for it that might put it back on the table in terms of putting it out there.”

But cattle producers still have their doubts

“There were considerable uncertainties as to the effectiveness of that vaccine,” said Reynold Bergen, the scientific director of the Canadian Cattlemen’s Association’s Beef Cattle Research Council, adding that the industry is studying other ways to reduce E. coli in cattle.

“E. coli shedding is a real concern for the industry,” he said.