Botulism: What you need to know

Botulism cases are rare in Canada but potentially serious. The culprit? A potent neurotoxin produced by Clostridium botulinum bacteria under certain conditions.

Infants are particularly vulnerable to dangerous foodborne illness

Canned foods that are dented or bulging, or jars with bulging lids, should raise concerns about the risk of bacteria that could cause botulism, public health authorities say. (Debora Cartagena/CDC)

Botulism cases are rare in Canada but potentially serious.

The culprit? A potent neurotoxin produced by Clostridium botulinum bacteria under certain conditions.

This week, Loblaw Companies Ltd. expanded a recall of PC Organics baby food pouches because they could permit the growth of Clostridium botulinum.

"A manufacturing error resulted in excess water in the product, which under certain circumstances could support the growth of Clostridium botulinum and pose a health risk to consumers, the Canadian Food Inspection Agency said in its updated food recall warning.

The illness is uncommon. There are fewer than seven cases per year across Canada. No deaths from botulism have been reported in Canada in the last five years, a spokeswoman for the Public Health Agency of Canada said.

Paralysis spreads downward

The botulinum toxin is an incredibly potent neurotoxin, said Dr. Doug Sider, medical director of communicable disease prevention and control at Public Health Ontario.

"Depending on the amount of toxin you take, that nerve action, the paralysis can spread from your head downwards," Sider said.

A computer-generated image depicts anaerobic, spore-forming, Clostridium bacteria. The clubbed shaped ones have entered what is known as an endospore phase, which is a tougher, dormant phase, resistant to heat and UV-radiation, according to the U.S. Centers for Disease Control and Prevention. (James Archer/CDC)

The affected person might have double vision, trouble speaking or swallowing, Sider said.

"If you see an adult with Clostridium botulinum toxicosis, you would think they were drunk," said Rick Holley, a retired professor of food science at the University of Manitoba.

If caught early, there's an antitoxin that can be injected into the patient that binds to the toxin and prevents paralysis, Sider said. If the person becomes paralyzed, they need to be in an ICU with respiratory support.

Long-lived spores

"Clostridium spores are notorious for being long-lived," said McMaster microbiologist Herb Schellhorn in Hamilton.

Part of the challenge is that the bacteria are common in the environment, such as dry soil in a backyard, on vegetable material or lake sediments where it can get into fish, said Holley.

The foodborne illness cases that do occur are largely from improperly preserved canned foods at home or improperly refrigerated meats, such as game stored for long periods in Canada's North, Sider said, referring to a literature review by Public Health Ontario.

The organism grows in the absence of oxygen, or what scientists call an anaerobic environment.

If the water content is too high, if the food isn't acidic enough, the environment is anaerobic and the C. botulinum bacteria have a sugar to feed on, then they can produce spores that grow, germinate and produce toxins, Sider said.

Infants are particularly vulnerable because the microbes in their gut aren't developed enough to outcompete C. botulinum when it's introduced, Schellhorn said.

For the same reason, infants under a year old shouldn't eat honey. Since their gut is underdeveloped, infants are susceptible to the bacterial spores that are sometimes found in honey, Holley said.

The bacteria can also take hold in adults with anatomical abnormalities in their gastrointestinal tract, such as after bowel surgery, Sider said. 

C. botulinum spores are heat resistant and require high heat treatment, preferably with pressure, to reduce growth.

Companies often use industrial pressure cookers to heat their products beyond boiling temperatures at high pressure for about 20 minutes.

The question in this latest recall of baby food is how the contamination occurred. Once that is identified, it should be publicized to encourage continued confidence in our food supply, Schellhorn suggested.

In the classic case of a bulging can, the product shouldn't be consumed.