Experts question role of walnuts in E. coli outbreak

By Sarah Schmidt and Aaron Derfel, Postmedia News
April 8, 2011 


The E. coli contiminated nuts were sold in bulk, as prepackaged walnut halves or crumbs, and as mixes of 'salad booster' or mixed nuts under several names, all distributed by Amira Enterprises.

OTTAWA — The walnut could be taking an unnecessary public-relations hit by being pegged as the likely source of an E. coli outbreak that has claimed one life in Quebec, a leading food-safety expert said Friday.

Food microbiologist Keith Warriner from the University of Guelph said there appear to be some unanswered questions in the federal government's food safety investigation, so he wouldn't be surprised if it turns out walnuts aren't to blame for an outbreak of E. coli in three provinces.

The Canadian Food Inspection Agency earlier this week recalled shelled walnut products imported from California by Montreal-based Amira Enterprises Inc., because they may be contaminated with E. coli bacteria. The agency took action based on information provided by the Canadian Public Health Agency and a risk assessment by Health Canada.

In fact, a senior public health official said Friday there is "no evidence" the Quebecer who died of E. coli illness actually ate any of the walnuts thought to be behind the outbreak.

"When we bring information from different people together, they share something in common, and in this particular case, we were looking at food consumption, and this individual did not fit the same pattern," said Dr. Mark Raizenne of the Public Health Agency of Canada.

Raizenne said that E. coli is "prevalent in the environment" and some people — especially those with weakened immune systems — can develop an infection, but it might not necessarily be related to tainted food that has caused a particular outbreak.

Quebec Health Department officials have said that the Quebecer who died was suffering from "significant" pre-existing health problems.

Since the recall, federal public-health authorities have confirmed 14 Canadians have been stricken with the same strain of E. coli with a matching fingerprint, including the fatal case in Quebec. The public health agency says walnuts are the suspected source of the outbreak, and is warning there may be walnuts other than those listed in CFIA's recall notice involved the outbreak.

To date, no Amira walnut product has tested positive for E. coli, according to CFIA. And of the 12 people who were able to provide information about their food consumption history to the Canadian Public Health Agency as part of the investigation, four people reported that they hadn't consumed walnuts.

Raizenne told Postmedia News on Friday that of the eight people who had consumed walnuts, all but one had eaten Amira brand walnuts.

"So we had eight cases that had consumed walnuts and seven of them were converged onto this one distributor," said Raizenne.

Those hit by the outbreak consumed foods typically associated with E. coli, such as ground beef, but there was no overlapping brand — meaning the "likely source based on the information that we have" is walnuts, said Raizenne.

Warriner isn't convinced.

"I've got a feeling it's going to be more like the tomato recall we had," he said Friday.

In 2008, there was a massive salmonella outbreak in the United States, leading to a very large recall of tomatoes in the U.S. and Canada. Initially, the Food and Drug Administration identified tomatoes from the U.S as the source but later confirmed that the source was jalapeno and serrano peppers from Mexico.

"It literally shut down the tomato industry, and after around five months of investigation, they said, 'No, it's not tomatoes, it's peppers.' And I've got a feeling that's going to happen in this case. The fact is walnuts and E. coli don't really go together that well," said Warriner, pointing out any recall is "really detrimental" to a business.

"It's a strange one because usually if you've got a product recall at this stage, you certainly want strong evidence," said Warriner.

Rick Holley, a food microbiologist and food-safety expert at the University of Manitoba, said CFIA, acting on the advice of public-health officials, made "the right call" based on the epidemiology evidence gathered to date.

"We value the Preliminary Chain Reaction that are used to generate patterns of genetic fingerprints from organisms as being very useful in establishing weight of evidence used in deciding whether we've got a common food source for an outbreak, and so to take action at this stage is responsible, given what we've got right now," said Holley.

"It's the right call. There is the normal uncertainty associated with a dietary recall in terms of a people's memory, no fault to the people in contributing the information."

Raizenne pointed out that the food safety investigation is ongoing, but the agency has a duty to warn the public about risks.

"The evidence is pointing us in this direction at this time and we are informing people," said Raizenne. "We're trying to prevent any further illnesses. That is the first and foremost objective in informing people of the cluster and the information that we have."

With files from the Montreal Gazette