- Home Canning and Botulism
- Botulism and Food Poisoning in Home Canning: What Causes It and How to Prevent It
- What is Botulism?
- How can you tell if there is botulism in your home canned foods, like green beans?
- How common is botulism?
- What are the Symptoms of Botulism Poisoning?
- Where does botulism come from?
- Why is botulism a concern in home canning? My kitchen is clean and everything gets sanitized!
- How can botulism be prevented?
- Can’t I simply heat the jars in a water bath canner for a very long time or add acid (vinegar or lemon juice)?
- Why can’t I use my own recipe?
- Are home-canned foods the only concern?
- What precautions should I take?
- Examples in the news:
- Are You At Risk for Foodborne Botulism?
- Is there any way to tell, before eating it, if a canned food has deadly botulism poisoning that will kill you?
- Symptoms of foodborne botulism
- Exposure and transmission
- Diagnosis and treatment
- WHO’s response
- Infant Botulism
- Botulism – including symptoms, treatment and prevention
- How botulism is spread
- Signs and symptoms
- Incubation period
- Infectious period
- Useful links
- Botulism: What You Don’t See or Smell Can Still Hurt You
Home Canning and Botulism
Home canning is an excellent way to preserve garden produce and share it with family and friends. But it can be risky—or even deadly—if not done correctly and safely.
It’s summertime and time to harvest the delicious produce you’ve been growing. You may be thinking about home canning as a way to preserve your garden goodies. But beware! If home canning is not done the proper way, your canned vegetables and fruits could cause botulism.
What is botulism?
Botulism is a rare but potentially deadly illness caused by a poison most commonly produced by a germ called Clostridium botulinum. The germ is found in soil and can survive, grow, and produce a toxin in certain conditions, such as when food is improperly canned. The toxin can affect your nerves, paralyze you, and even cause death.
You cannot see, smell, or taste botulinum toxin—but taking even a small taste of food containing this toxin can be deadly.
What’s a low-acid food?
Low-acid foods have a pH level greater than 4.6, which means they are not acidic enough to prevent the growth of botulinum bacteria. Examples are:
- Green beans
- Some tomatoes *
- All meats
- Fish and seafood
*Tomatoes require added acidExternal – lemon juice or citric acid – for safe home canning.
What are the symptoms of botulism?
Botulism is a medical emergency. If you or someone you know has symptoms of foodborne botulism, see your doctor or go to the emergency room immediately.
Symptoms may include the following:
- Double vision
- Blurred vision
- Drooping eyelids
- Slurred speech
- Difficulty swallowing
- A thick-feeling tongue
- Dry mouth
- Muscle weakness
How can I keep myself and others safe when it comes to home-canned foods?
Many cases of foodborne botulism have happened after people ate home-canned, preserved, or fermented foods that were contaminated with toxin. The foods became contaminated because they were not canned (processed) correctly.
You can take steps to protect yourself, your family, and others when it comes to home-canned foods by following these tips:
1. Use proper canning techniques.
The best way to prevent foodborne botulism is by carefully following instructions for safe home canning in the USDA Complete Guide to Home CanningExternal. Do not follow recipes and cookbooks that do not follow the steps in the USDA guide, even if you got these items from a trusted friend or family member.
You can learn more about proper home canning from these resources:
- The National Center for Home Food PreservationExternal
- State and county extension servicesExternal (click on your state or scroll down for a list of all services)
2. Use the right equipment for the kind of foods that you are canning.
Pressure canning is the only recommended method for canning low-acid foods. Foods with low acid content are the most common sources of home-canning related botulism cases. Low-acids foods include almost every vegetable, some fruits, milk, all meats, fish, and seafood. See box to the right for examples. Do not use boiling water canners for low-acid foods because they will not protect against botulism.
Always use a properly sized pressure canner that meets USDA recommendations for pressure canning Cdc-pdfExternal when canning low-acid foods. Contact your state or county extension serviceExternal to find out if your pressure canner meets USDA recommendations.
Make your home-canned vegetables, meats safe
- Use a recommended pressure canner that holds at least four one-quart jars sitting upright on the rack.
- Be sure the gauge of the pressure canner is accurate. Gauges may be checked at many county Cooperative Extension offices or contact the pressure canner manufacturer for other options.
- Clean lid gaskets and other parts according to the manufacturer’s directions.
- Vent the pressure canner before pressurizing and follow recommended cooling steps.
- Use up-to-date process times and pressures for the kind of food, the size of jar, and the method of packing food in the jar.
3. When in doubt, throw it out!
If there is any doubt if safe canning guidelines have been followed, do not eat the food. Home-canned and store-bought food might be contaminated with toxin or other harmful germs if
- the container is leaking, bulging, or swollen;
- the container looks damaged, cracked, or abnormal;
- the container spurts liquid or foam when opened;
- the food is discolored, moldy, or smells bad.
If the container or the food inside has any signs of contamination, throw it out! If any of the food spills, wipe up the spill using a solution of 1/4 cup bleach for each 2 cups of water.
Never taste food to determine if it is safe. Do not taste or eat food that is discolored, moldy, or smells bad. Do not taste or eat food from cans that are leaking, have bulges or are swollen, or look damaged, cracked, or abnormal. Do not taste or eat food from a can that spurted liquid or foam when it was opened. Learn more >
— After a botulism outbreak following a church potluck in Ohio left a woman dead and sickened up to 28 others, health officials say canned food could be to blame.
Officials are looking into canned fruits and vegetables as well as pasta and potatoes salads and other menu items, according to Ohio Department of Health spokeswoman Shannon Libby.
So, you may be wondering how to keep your pantry safe in time for picnic season.
Here’s what you need to know:
Botulism is caused by a nerve toxin released by certain bacteria, according to the U.S. Centers for Disease Control and Prevention.
“All forms of botulism can be fatal and are considered medical emergencies,” according to the CDC. “Foodborne botulism is a public health emergency because many people can be poisoned by eating a contaminated food.”
Symptoms can take between 6 hours and 10 days to arise, and they include double vision or blurred vision, drooping eyelids, slurred speech, difficulty swallowing and muscle weakness, according to the National Institutes of Health.
How common is it?
“Botulism has virtually been eliminated in this country,” said Dr. William Schaffner, chairman of preventive medicine at Vanderbilt University Medical Center in Nashville, Tennessee.
There are about 145 cases a year in the U.S., according to the CDC. Only 15 percent of those are foodborne. The rest are either wound-related because botulism lives in the dirt, or something called infant botulism, in which babies with no botulism antibodies somehow consume a small amount of the spores, said Dr. Frank Esper, an infectious diseases expert at UH Case Medical Center in Cleveland, Ohio.
“It’s why we’re not allowed to give honey to children under 1 year of age,” Esper said. “A small amount of botulism can be found there.”
He said most people have some resistance to botulism in small amounts, but infants have no antibodies.
Why is it found in canned goods?
The bacteria Clostridium botulinum releases the toxin that causes botulism as part of its natural anaerobic process, meaning it multiplies in an oxygen-free environment, like a sealed can, Schaffner said.
“Back in the day when there was a lot of home-canning, people didn’t always meticulously follow protocols,” Schaffner said. “The spores were not killed and given that this was now an environment in a sealed container, the bacteria could multiply and produce the toxin.”
With the advent of commercial canning and better understanding of botulism to put food safety procedures in place, he said it’s now rare to have a canned good-related botulism outbreak.
What can you do to stay safe?
Unless the Ohio potluck investigators find that the food that caused the illness was commercially canned, Schaffner said people have nothing to worry about. But if they see a can that is puffy or dented, discard it.
“Spoilage of one kind or another likely occurred,” he said. “There’s no reason to subject yourself to any kind of chance of getting sick.”
Botulism and Food Poisoning in Home Canning: What Causes It and How to Prevent It
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What is Botulism?
Botulism is the name of the type of food poisoning we get consuming the toxin produced by active Clostridium botulinium in foods. It is caused by a toxin that attacks the body’s nerves and causes difficulty breathing, muscle paralysis, and even death. This toxin is made by Clostridium botulinum and sometimes Clostridium butyricum and Clostridium baratii bacteriaBotulism was formerly known as “Kerner’s Disease.” It was named after the man who signed the death certificate of people who ate contaminated sausage and died in an outbreak in Germany. In fact, botulism comes from the Latin word, botulus, which means sausage. Botulism is a rare but serious foodborne disease. It can be fatal. There are two different types of botulism poisoning that we need to be concerned with – adult and infant botulism.
Note: if you are looking for another pathogen (salmonella, Staph, etc.) see this page.
How can you tell if there is botulism in your home canned foods, like green beans?
The answer is, unless you have access to a food science laboratory, you can’t. In this news story, Lizann Powers-Hammond, a food safety and preservation expert with Washington State University Extension says: “People always want to know if they can look at a jar of food to know if it’s okay. But I can’t tell by looking. What I need to know is the food’s history. How it was canned.”
How common is botulism?
In the United States, an average of 145 cases are reported each year. Of these, approximately 15% are foodborne, 65% are infant botulism, and 20% are wound. Adult intestinal colonization and iatrogenic botulism also occur, but rarely. Outbreaks of foodborne botulism involving two or more persons occur most years and usually caused by eating contaminated home-canned foods. The number of cases of foodborne and infant botulism has changed little in recent years, but wound botulism has increased because of the use of black-tar heroin, especially in California.
While commercially canned goods are required to undergo a “botulinum cook” at 121 °C (250 °F) for 3 minutes, and so rarely cause botulism (while home pressure canning equipment only can reach 240 °F), there have been notable exceptions such as the 1978 Alaskan salmon outbreak and the 2007 Castleberry’s Food Co. outbreak.
Foodborne botulism has more frequently been from home-canned foods with low acid content, such as carrot juice, asparagus, green beans, beets, and corn.
However, outbreaks of botulism have resulted from more unusual sources. In July, 2002, fourteen Alaskans ate muktuk (whale meat) from a beached whale, and eight of them developed symptoms of botulism, two of them requiring mechanical ventilation . Other sources of infection include garlic or herbs stored covered in oil without acidification, chili peppers, improperly handled baked potatoes wrapped in aluminum foil, and home-canned or fermented fish. Persons who do home canning should follow strict hygienic procedures to reduce contamination of foods. Oils infused with garlic or herbs should be refrigerated. Potatoes which have been baked while wrapped in aluminum foil should be kept hot until served or refrigerated. Because the botulism toxin is destroyed by high temperatures, home-canned foods are best boiled for 20 minutes before eating. Metal cans containing food in which bacteria, possibly botulinum, are growing may bulge outwards due to gas production from bacterial growth; such cans should be discarded. Any container of food which has been heat-treated and then assumed to be airtight which shows signs of not being so, e.g., metal cans with pinprick holes from rust or mechanical damage, should also be discarded. a potato should be COOKED at the given time.
What are the Symptoms of Botulism Poisoning?
Normal symptoms of food-borne botulism usually occur between 12-38 hours after consuming the botulinum toxin. However, they can occur as early as 6 hours or as late as 10 days after.
Normal symptoms usually start with weakness of the muscles that control the eyes, face, mouth, and throat. This weakness may spread to the neck, arms, torso, and legs. The symptoms include dry mouth, double and/or blurred vision, difficulty swallowing, muscle weakness, drooping eyelids, difficult breathing, slurred speech, vomiting, urinary incontinence and sometimes diarrhea. These symptoms may continue to cause paralytic ileus with severe constipation, and will lead to body paralysis. The respiratory muscles are affected as well, which may cause death due to respiratory failure. These are all symptoms of the muscle paralysis caused by the bacterial toxin.
In all cases illness is caused by the toxin made by C. botulinum, not by the bacterium itself. The pattern of damage occurs because the toxin affects nerves that are firing more often.
Where does botulism come from?
C. botulinum is found in soil all over the world. The bacteria have the ability to form a spore (like a tiny, microscopic seed) that is very resistant to heat and chemicals. The bacteria grow best anaerobically; that means it will grow without air. The spores activated in the absence of air (as is present in a jar or can of sealed food) produce a toxin. This toxin is the most deadly known to food scientists. C. botulinum will not grow in acidic conditions (pH less than 4.6), and therefore the toxin will not be formed in acidic foods (however, a low pH will not degrade any pre-formed toxin). Combinations of low storage temperature and salt contents and/or pH are also used to prevent the growth of the bacteria or the formation of the toxin.
Why is botulism a concern in home canning? My kitchen is clean and everything gets sanitized!
Clostridium botulinum bacteria exist either as spores or as vegetative cells. The spores, which are dormant and comparable to plant seeds, can survive harmlessly in soil and water for many years. When ideal conditions exist for growth, the spores produce vegetative cells which multiply rapidly and may produce a deadly toxin within three to four days of growth in an environment consisting of:
- a moist, low-acid food (like meats, almost all vegetables – including peppers, green beans, corn, etc.)
- a temperature between 40° and 120°F
- less than 2 percent oxygen (which occurs in any jar of canned food)
Botulism spores are present on most fresh food surfaces. The botulinum toxin has been found in a variety of foods, including low-acid preserved vegetables, such as green beans, spinach, mushrooms, and beets; fish, including canned tuna, fermented, salted and smoked fish; and meat products, such as ham and sausage. The food implicated differs between countries and reflects local eating habits and food preservation procedures. Occasionally, commercially prepared foods are involved. Because they grow only in the absence of air, they are harmless on fresh foods. Most bacteria, yeasts, and molds are difficult to remove from food surfaces. Washing fresh food reduces their numbers only slightly. Peeling root crops, underground stem crops, and tomatoes reduces their numbers greatly. Blanching also helps, but the vital controls are the method of canning and making sure the recommended research-based process times are used.
How can botulism be prevented?
While the incidence is fairly rare, the death rate is high if not treated immediately. Prevention is obviously extremely important. Home canning should follow strict hygienic recommendations to reduce risks. Pressure canners should be used for all low-acid foods, but home pressure canners only reach 240 F, not 250 like commercial equipment, and are not hot enough to kill ALL of the spores. It is the destruction of the active bacteria, and destruction or substantial reduction in numbers of spores along with the creation of an environment that is less conducive to the growth of the remaining spores, that ensures safety.
The botulism spores can only be killed by the high heat which can be obtained in a pressure canner. Water bath canners cannot do this. The toxin (that is produced in anaerobic conditions) can only be destroyed by boiling; so if there is any doubt, boiling the food for 20 minutes after opening the jars adds an additional measure of safety, although this is not always practical. Colorado State University says:
As an added precaution, boil all home-canned vegetables and meats without tasting for 10 minutes plus one minute per 1,000 feet above sea level (15 minutes at 5,000 feet). Boil home-canned spinach and corn 20 minutes before tasting. If the food looks spoiled, foams or has an off odor during heating, discard it.
The processing times in recipes in PickYourOwn.org are from the USDA and Ball Blue Book, and ensure destruction of the largest expected number of heat-resistant microorganisms in home-canned foods. Properly processed, home canned food will be free of spoilage if lids seal and jars are stored below 95°F. Storing jars at 50° to 70°F also enhances retention of quality.
See this page for why and how to choose a canner and see this page for canning recipes that are based on the USDA recommendations.
Can’t I simply heat the jars in a water bath canner for a very long time or add acid (vinegar or lemon juice)?
Botulism spores are very heat resistant. They may be destroyed at boiling water temperatures, but extremely long times are required. The higher the canner temperature, the more easily and quickly they are destroyed.
Low acid foods
Therefore, all low-acid foods should be sanitized at temperatures of 240° to 250°F, attainable with pressure canners operated at 10 to 15 PSI. PSI means pounds per square inch of pressure as measured by a gauge. At these temperatures, the time needed to destroy bacteria in low-acid canned food ranges from 20 to 100 minutes. The exact time depends on the kind of food being canned, the way it is packed into jars, and the size of jars.
The time needed to safely process low-acid foods in a boiling water canner ranges from 7 to 11 hours. Such long processing times are not researched and are not recommended. Losses in nutrients and quality would be unacceptable. The time needed to process acid foods in boiling water varies from 5 to 85 minutes.
Why can’t I use my own recipe?
How would you know it was safe? How long should you process it? In what type of canner? How could you be sure the botulism spores were destroyed (you can’t see them with the naked eye)?
See this page for a more detailed answer!
The many factors involved make it impossible to estimate the correct processing conditions for any food product. This is especially true for items which are mixtures of food with differing water content, piece size, fat content, or acidity as well as types and numbers of microorganisms present. The establishment of a correct, safe process requires laboratory research by trained scientists.
Are home-canned foods the only concern?
Infant botulism is a concern for children under one year of age. It is possible for bees to pick up the botulism spores from flowers or soil. These spores are not destroyed during the processing for honey. The botulism spores grow in the baby’s intestinal tract and then produce the toxin. After the age of one year, this no longer happens because of higher acid levels in the baby’s tummy. This is why you should not give babies (under 1 year old) any honey!
Flavored oils can be a special concern if not prepared correctly. When herbs, garlic, or tomatoes are placed in oils, the botulism spores on the plant material can start to produce the toxin in this anaerobic (oxygenless) mixture. To be safe, keep these flavored oils refrigerated and make only the amount of herbal oils and butters that will be used in a few days. Using dried herbs and vegetables will also reduce the risk.
Baked potatoes wrapped in foil and kept at room temperature can also form the anaerobic conditions the botulism spores need to produce their toxin. For this reason, leftover potatoes should be refrigerated. Potato salad made from leftover baked potatoes has been implicated in botulism poisoning.
What precautions should I take?
- Store your home canned foods at temperatures below 95°F. Storing jars at temperatures bewteen 50° – 70°F further maintains taste, color and overall quality.
- Discard all raw or canned food that shows any sign of being spoiled.
- Discard all bulging or swollen cans of food and food from glass jars with bulging lids.
- Use only tested approved recipes (Ball Blue Book, USDA, University Extension service, etc. (All recipes on PickYourOwn are from these, unless specifically noted)
- Do not deviate substantially from the approved recipes. Adding another teaspoon of spice or substituting one spice is usually fine, but changing base ingredients or substantially changing proportions or steps is dangerous, particularly with regard to acidifiers (lemon juice, vinegar, citric acid, etc.)
- Do NOT invent your own recipe; unless you have access to a food science laboratory to culture and test it.
- DO NOT TASTE food from swollen containers or food that is foamy or has a bad odor.
- Process low-acid foods at temperatures above boiling (which can only occur under pressure) and for the recommended time for the size of can or jar you are using.
- Do not assume that the pressure canners renders all low acid foods safe. Home pressure canners are not as hot as commercial equipment, so some food simply cannot be safely canned at home. Pureed pumpkin and foods made from pumpkin puree, like pumpkin butter is a clear example of a food that is unsafe to can at home.
- Do not assume that adding vinegar, lemon juice, citric acid, or other acids will make low acid foods safe to can in a water bath canner.
- DO can low-acid foods in a pressure canner, following an approved recipe. Do not can low-acid foods in the oven, in water-bath, open kettle or vegetable cooker.
- Clean all surfaces with chlorine/water solution (one tablespoon of bleach per gallon of water) that leaky containers may have contaminated . Then discard any sponges or cloths used for cleanup.
- Do not give honey or foods with honey to infants under one year of age.
- National Center for Disease Control, Center for Disease Control and Prevention (CDC)
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, The Bad Bug Book.
- Clemson University Extension.
- Ohio State university Extension
- Oil Infusions and the Risk of Botulism, Colorado State University Cooperative Extension, Safefood new – Summer 1998 – Vol 2 / No. 4
- “Botulism Linked to Baked Potatoes”.
- ” Safe Home Canning of Fruits, Vegetables and Meats” – University of Minnesota
- How Microorganisms Affect Food Safety and Quality – Virginia Tech
- Center for Disease Control
- Effect of temperature on spore germination and vegetative cell growth of Clostridium botulinum.
For more information on food borne illness, contact your local county Extension Agent .
Examples in the news:
Botulism blamed on improper home-canning
February 27, 2009 – The Spokesman-Review, John Stucke – “A serious case of botulism in Spokane has prompted warnings from food preservation experts and health officials to follow strict safety rules when canning vegetables at home. A nurse in her 30s, along with two children younger than 10, were stricken with the nerve toxin after eating improperly canned green beans from a backyard garden. All three were given an antitoxin that was flown to Spokane from a special storage facility in Seattle. Special precautions must be taken when canning low-acid foods such as green beans and asparagus. Since most vegetables don’t have enough natural acidity to kill the bacteria, they must be canned using a pressure canner that can reach high temperatures. Or, vegetables may be pickled with enough vinegar to inhibit growth of the bacteria. As a safety precaution, canned vegetables should be boiled for 11 minutes at Spokane’s elevation before eating. Foods that were not canned following U.S. Department of Agriculture standards should be thrown away before opening.” .
Botulism in garlic with oil / refrigerated without heat processing first
Three people were hospitalized with botulism after eating a chopped garlic-in-oil mix that had been used in a spread for garlic bread in Kingston, New York. The bottled chopped garlic spread relied solely on refrigeration to ensure safety. The FDA has ordered companies to stop making the product. Most of the 10 to 30 outbreaks reported annually in the United States are associated with home canned foods. Occasionally, commercially produced foods have been involved in outbreaks. Source: The Bad Bug Book (US Government publication)
Are You At Risk for Foodborne Botulism?
Foodborne illnesses affect more than 76 million people in the United States each year, according to the National Institutes of Health, and one of the most serious types is botulism. The most recent outbreak left one person dead and at least 23 others hospitalized after exposure to the foodborne bacteria at a church potluck.
Caused by the bacterium Clostridium botulinum, botulism is a relatively rare condition — only about 145 cases are reported to the U.S. federal government each year, and of these, only 15 percent are foodborne. But the most recent outbreak demonstrates just how serious the illness can be.
Those who have it could be in serious danger if they do not seek treatment promptly, says Robynne Chutkan, MD, assistant professor in the division of gastroenterology at Georgetown University Medical Center in Washington, D.C.
“It’s the same bacteria that they make Botox from to smooth out wrinkles,” Dr. Chutkan says. “Clostridium botulinum produces a neurotoxin that paralyzes the nerves in the body. Eventually it can affect the respiratory muscles, and people can stop breathing.”
Unlike many other foodborne illnesses, botulism is not contagious. People generally acquire it through eating food that is contaminated with the bacteria. The botulinum spores thrive and multiply into toxin-producing cells in low-acid environments with very little oxygen, so improperly canned low-acid foods, such as vegetables and cured meats, are often the cause of foodborne botulism. “It doesn’t typically happen with fresh food, since the bacteria really need an environment that contains a low level of oxygen,” Chutkan says. That’s why home canning is a potential culprit.
Clostridium botulinum also occurs naturally in dust and dirt, as well as in honey. In some cases, infants can develop botulism by ingesting Clostridium botulinum spores. Older children and adults who ingest the spores this way can usually process them without trouble. But an infant’s immature digestive system may allow the spores to multiply, causing the same neurotoxic effects as foodborne botulism.
How to Recognize Botulism Symptoms
Botulism symptoms usually begin about 18 to 36 hours after eating contaminated food. Signs of botulism include weak muscles, drooping eyelids, and double vision. In rare cases, you may also experience nausea and vomiting. Infants with botulism may show signs such as weak cries, constipation, a flat facial expression, and difficulty breathing.
If you have any of these botulism symptoms, you should immediately go to the nearest hospital, Chutkan says. An antitoxin that blocks the action of the neurotoxin can be administered. In severe cases, a ventilator can be used to keep the body supplied with oxygen until the breathing muscles begin to work again.
Preventing Botulism: Safeguards to Practice
While there is no fail-safe way to prevent botulism, there are ways to greatly reduce your risk of developing it. When canning food at home, follow all safe-canning principles, such as washing fresh food, sterilizing jars, and canning low-acid foods with a pressure canner at very high temperatures. Using old-fashioned canning jars with wire bails is not recommended because they may not seal properly.
If you buy or make flavored oils, such as garlic-infused olive oil, refrigerate them rather than storing at room temperature, which could lead to the growth of Clostridium botulinum.
To reduce the risk of infant botulism, don’t give honey to children under 1 year of age, since it is a known source of Clostridium botulinum. Processed foods that contain honey, such as honey graham crackers, should also be avoided in this age group. There is also a remote possibility that corn syrup may contain botulinum spores, so check with your doctor before giving it to your baby.
While botulism is rare, it does occur. Take precautions, and if you suspect you’ve been exposed to the bacteria, seek fast medical attention.
Is there any way to tell, before eating it, if a canned food has deadly botulism poisoning that will kill you?
I am very familiar with this can. I was part of the team 45 years ago this week, searching for these cans in food outlets, following the death of a banker in New Jersey from botulism. I still have one of these cans.
The problem was under-processing; perhaps a few degrees too low or a few minutes too short, but the required time-temperature combination (a theoretical 12-log decrease or a “12-D process”) simply wasn’t reached, and no-one sounded the alarm.
The question asks if there is any way to detect botulinum neurotoxin (BoNT) in the food before it is eaten. The lab can detect it, of course, but the consumer has a chance of detecting it only when the growth of C. botulinum produces obvious signs of bacterial action. When this occurs, the signs are as follows:
1. In the Unopened can, this would show as internal pressure: the ends of the can are convex instead of normally concave. When shaken, liquid food will sound like liquid combined with abundant gas or “air”
2. In the can being opened: the contents will typically spurt out or ‘fizz’, instead of air rushing IN to the normal can which has maintained a vacuum.
3. The contents may be foul-smelling, discoloured, obviously suspicious.
BUT, C. botulinum can grow sufficiently to produce a toxin but not to the extent that the bacteria will have changed the food’s appearance or odour OR TASTE. This is thought to be the circumstance that July evening in 1971, in Newark. New Jersey. Vichyssoise is a sieved potato cream soup, mild-tasting, served cold, and obvious decomposition would have been evident. Note too, that strong-tasting or unfamiliar-tasting foods may mask the early decomposition effects.
The take-away points in this discussion are
* DO NOT use any can that is swollen, or the contents under pressure when opened
* You CANNOT tell in the early stages if the can or jar contains BoNT
As a final fact, this is one food toxin that CAN BE neutralized by heat. Even though the bacterial spores will survive very high temperatures, the toxin will be destroyed by raising all parts of the food to 212F or 100C (boiling point) for a few minutes. (Note that the Vichyssoise was designed to be eaten at room temperature, without heating). The commercial canning industry has a remarkable record of safety, and this one episode was a very rare event. Almost every incidence of food-borne botulism arises from improperly processed home-canned foods.
Foodborne botulism is a serious, potentially fatal disease. However, it is relatively rare. It is an intoxication usually caused by ingestion of potent neurotoxins, the botulinum toxins, formed in contaminated foods. Person to person transmission of botulism does not occur.
Spores produced by the bacteria Clostridium botulinum are heat-resistant and exist widely in the environment, and in the absence of oxygen they germinate, grow and then excrete toxins. There are 7 distinct forms of botulinum toxin, types A–G. Four of these (types A, B, E and rarely F) cause human botulism. Types C, D and E cause illness in other mammals, birds and fish.
Botulinum toxins are ingested through improperly processed food in which the bacteria or the spores survive, then grow and produce the toxins. Though mainly a foodborne intoxication, human botulism can also be caused by intestinal infection with C. botulinum in infants, wound infections, and by inhalation.
Symptoms of foodborne botulism
Botulinum toxins are neurotoxic and therefore affect the nervous system. Foodborne botulism is characterized by descending, flaccid paralysis that can cause respiratory failure. Early symptoms include marked fatigue, weakness and vertigo, usually followed by blurred vision, dry mouth and difficulty in swallowing and speaking. Vomiting, diarrhoea, constipation and abdominal swelling may also occur. The disease can progress to weakness in the neck and arms, after which the respiratory muscles and muscles of the lower body are affected. There is no fever and no loss of consciousness.
The symptoms are not caused by the bacterium itself, but by the toxin produced by the bacterium. Symptoms usually appear within 12 to 36 hours (within a minimum and maximum range of 4 hours to 8 days) after exposure. Incidence of botulism is low, but the mortality rate is high if prompt diagnosis and appropriate, immediate treatment (early administration of antitoxin and intensive respiratory care) are not given. The disease can be fatal in 5 to 10% of cases.
Exposure and transmission
C. botulinum is an anaerobic bacterium, meaning it can only grow in the absence of oxygen. Foodborne botulism occurs when C. botulinum grows and produces toxins in food prior to consumption. C. botulinum produces spores and they exist widely in the environment including soil, river and sea water.
The growth of the bacteria and the formation of toxin occur in products with low oxygen content and certain combinations of storage temperature and preservative parameters. This happens most often in lightly preserved foods and in inadequately processed, home-canned or home-bottled foods.
C. botulinum will not grow in acidic conditions (pH less than 4.6), and therefore the toxin will not be formed in acidic foods (however, a low pH will not degrade any pre-formed toxin). Combinations of low storage temperature and salt contents and/or pH are also used to prevent the growth of the bacteria or the formation of the toxin.
The botulinum toxin has been found in a variety of foods, including low-acid preserved vegetables, such as green beans, spinach, mushrooms, and beets; fish, including canned tuna, fermented, salted and smoked fish; and meat products, such as ham and sausage. The food implicated differs between countries and reflects local eating habits and food preservation procedures. Occasionally, commercially prepared foods are involved.
Though spores of C. botulinum are heat-resistant, the toxin produced by bacteria growing out of the spores under anaerobic conditions is destroyed by boiling (for example, at internal temperature greater than 85 °C for 5 minutes or longer). Therefore, ready-to-eat foods in low oxygen-packaging are more frequently involved in cases of foodborne botulism.
Food samples associated with suspect cases must be obtained immediately, stored in properly sealed containers, and sent to laboratories in order to identify the cause and to prevent further cases.
Infant botulism occurs mostly in infants under 6 months of age. Different from foodborne botulism caused by ingestion of pre-formed toxins in food, it occurs when infants ingest C. botulinum spores, which germinate into bacteria that colonize in the gut and release toxins. In most adults and children older than about 6 months, this would not happen because natural defences in intestines that develop over time prevent germination and growth of the bacterium.
C. botulinum in infants include constipation, loss of appetite, weakness, an altered cry and a striking loss of head control. Although there are several possible sources of infection for infant botulism, spore-contaminated honey has been associated with a number of cases. Parents and caregivers are therefore warned not to feed honey to the infants before the age of 1 year.
Wound botulism is rare and occurs when the spores get into an open wound and are able to reproduce in an anaerobic environment. The symptoms are similar to the foodborne botulism, but may take up to 2 weeks to appear. This form of the disease has been associated with substance abuse, particularly when injecting black tar heroin.
Inhalation botulism is rare and does not occur naturally, for example it is associated with accidental or intentional events (such as bioterrorism) which result in release of the toxins in aerosols. Inhalation botulism exhibits a similar clinical footprint to foodborne botulism. The median lethal dose for humans has been estimated at 2 nanograms of botulinum toxin per kilogram of bodyweight, which is approximately 3 times greater than in foodborne cases.
Following inhalation of the toxin, symptoms become visible between 1–3 days, with longer onset times for lower levels of intoxication. Symptoms proceed in a similar manner to ingestion of botulinum toxin and culminate in muscular paralysis and respiratory failure.
If exposure to the toxin via aerosol inhalation is suspected, additional exposure to the patient and others must be prevented. The patient’s clothing must be removed and stored in plastic bags until it can be washed thoroughly with soap and water. The patient should shower and be decontaminated immediately.
Other types of intoxication
Waterborne botulism could theoretically result from the ingestion of the pre-formed toxin. However, as common water treatment processes (such as boiling, disinfection with 0.1% hypochlorite bleach solution) destroy the toxin, the risk is considered low.
Botulism of undetermined origin usually involves adult cases where no food or wound source can be identified. These cases are comparable to infant botulism and may occur when the normal gut flora has been altered as a result of surgical procedures or antibiotic therapy.
Adverse effects of the pure toxin have been reported as a result of its medical and/or cosmetic use in patients, see more on ‘Botox’ below.
The bacterium C. botulinum is the same bacterium that is used to produce Botox, a pharmaceutical product predominantly injected for clinical and cosmetic use. Botox treatments employ the purified and heavily diluted botulinum neurotoxin type A. Treatment is administered in the medical setting, tailored according to the needs of the patient and is usually well tolerated although occasional side effects are observed.
Diagnosis and treatment
Diagnosis is usually based on clinical history and clinical examination followed by laboratory confirmation including demonstrating the presence of botulinum toxin in serum, stool or food, or a culture of C. botulinum from stool, wound or food. Misdiagnosis of botulism sometimes occurs as it is often confused with stroke, Guillain-Barré syndrome, or myasthenia gravis.
Antitoxin should be administered as soon as possible after a clinical diagnosis. Early administration is effective in reducing mortality rates. Severe botulism cases require supportive treatment, especially mechanical ventilation, which may be required for weeks or even months. Antibiotics are not required (except in the case of wound botulism). A vaccine against botulism exists but it is rarely used as its effectiveness has not been fully evaluated and it has demonstrated negative side effects.
Prevention of foodborne botulism is based on good practice in food preparation particularly during heating/sterilization and hygiene. Foodborne botulism may be prevented by the inactivation of the bacterium and its spores in heat-sterilized (for example, retorted) or canned products or by inhibiting bacterial growth and toxin production in other products. The vegetative forms of bacteria can be destroyed by boiling but the spores can remain viable after boiling even for several hours. However, the spores can be killed by very high temperature treatments such as commercial canning.
Commercial heat pasteurization (including vacuum packed pasteurized products and hot smoked products) may not be sufficient to kill all spores and therefore the safety of these products must be based on preventing bacterial growth and toxin production. Refrigeration temperatures combined with salt content and/or acidic conditions will prevent the growth of the bacteria and formation of toxin.
The WHO Five Keys to Safer Food serve as the basis for educational programmes to train food handlers and educate the consumers. They are especially important in preventing food poisoning.
The Five Keys are:
- keep clean
- separate raw and cooked
- cook thoroughly
- keep food at safe temperatures
- use safe water and raw materials.
Botulism outbreaks are rare but are public health emergencies that require rapid recognition to identify the disease source, distinguish outbreak types (between natural, accidental or potentially deliberate), prevent additional cases and effectively administer treatment to affected patients.
Successful treatment depends significantly on early diagnosis and the rapid administration of the botulinum antitoxin.
WHO’s role in responding to outbreaks of botulism that may be of international concern is as follows.
Surveillance and detection: WHO supports the strengthening of national surveillance and international alert systems to ensure rapid local outbreak detection and an efficient international response. WHO’s main tool for these activities of surveillance, coordination and response is the use of the International Network of Food Safety Authorities (INFOSAN) which links national authorities in Member States in charge of managing food safety events. This network is managed jointly by FAO and WHO.
Risk assessment: WHO response is based on a risk assessment methodology that includes consideration of whether the outbreak is natural, accidental, or, possibly, intentional. WHO also provides scientific assessments as basis for international food safety standards, guidelines and recommendations developed by the Codex Alimentarius Commission.
Containment at the disease source: WHO coordinates with national and local authorities in order to contain outbreaks at their source.
Delivery of assistance: WHO coordinates between international agencies, experts, national laboratories, airlines and commercial organizations to mobilize response equipment, materials and supplies, including the provision and administration of botulinum antitoxin.
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Infant botulism is an illness that can happen when a baby ingests bacteria that produce a toxin inside the body.
The condition can be frightening because it can cause muscle weakness and breathing problems. But it is very rare: Fewer than 100 cases of infant botulism happen each year in the United States, and most babies who do get botulism recover fully.
Infant botulism is treatable, but because of its severity, it’s important to learn the symptoms so you can recognize it early. Also know that honey is a known source of the bacteria spores that cause botulism. For this reason, honey shouldn’t be given to babies younger than 1 year old.
About Infant Botulism
This illness usually affects babies who are between 3 weeks and 6 months old, but all babies are at risk for it until their first birthdays.
Spores of Clostridium botulinum bacteria, found in dirt and dust, can contaminate honey. These bacteria are harmless to older kids and adults because their mature digestive systems can move the spores through the body before they cause any harm.
But very young babies haven’t developed the ability to handle the spores yet. So if an infant ingests them, the bacteria germinate, multiply, and produce a toxin. That toxin interferes with the normal interaction between the muscles and nerves and can hamper an infant’s ability to move, eat, and breathe.
Two other types of botulism tend to affect older kids and adults:
- wound botulism, when the bacteria infect a wound and produce the toxin inside of it
- foodborne botulism, which is usually caused by eating home-canned foods that contain the toxin
Signs and Symptoms
Symptoms of botulism begin between 3 to 30 days after an infant ingests the spores. Constipation is often the first sign of botulism that parents notice (although there are many other causes of constipation). Call your doctor if your baby hasn’t had a bowel movement in 3 days.
Other symptoms of botulism can include:
- flat facial expression
- poor feeding (weak sucking)
- weak cry
- decreased movement
- trouble swallowing with excessive drooling
- muscle weakness
- breathing problems
Infant botulism can be treated, but it’s important to get medical care as soon as possible. Call your doctor right away and seek medical attention if you see any of the warning signs in your baby.
Infant botulism is treated in the hospital, usually in the intensive care unit (ICU), where doctors will try to limit the problems the toxin causes in the baby’s body. The toxin can affect the breathing muscles, so doctors may put the infant on a ventilator. Because the toxin can affect the swallowing muscles, they may give the baby intravenous (IV) fluids or feedings through a tube to provide nourishment.
An antitoxin is now available for the treatment of infant botulism, called botulism immune globulin intravenous (BIGIV), which should be given as soon as possible. Babies with botulism who have received BIGIV recover sooner and spend less time in the hospital.
With early diagnosis and proper medical care, a baby should fully recover from the illness.
Like many germs, the Clostridium botulinum spores that cause botulism in infants are everywhere in the environment. They’re in dust and dirt, and even in the air. Experts don’t know why some infants contract botulism while others don’t.
One way to reduce the risk of botulism is to not give infants honey or any processed foods containing honey before their first birthday. Honey is a proven source of the bacteria and has led to botulism in infants who’ve ingested it. Light and dark corn syrups were thought to be a source of spores, but no proven cases of infant botulism have been linked to them. However, check with your doctor before giving these to your baby.
Reviewed by: Rebecca L. Gill, MD Date reviewed: January 2015
Botulism – including symptoms, treatment and prevention
Botulism is an illness caused by botulinum toxin or other similar toxins. Botulinum toxin is made by Clostridium botulinum bacteria and some other similar bacteria. The bacteria are widespread in the environment as spores. Spores are dormant forms of bacteria which are resistant to heat and drying. Under specific conditions, the spores of the bacteria germinate and make toxin.
Botulism is a notifiable condition1
How botulism is spread
Botulism may occur in several ways:
- Foodborne botulism may result from eating food contaminated with the toxin. This may be from poorly processed canned or bottled low acid foods, fermented foods or lightly preserved foods.
- Infant botulism results from the germination of ingested spores (for example, from honey or soil) inside the bowels of infants.
- Intestinal botulism results from the germination of ingested spores inside the bowels of people with altered bowel bacteria.
- Wound botulism results from spore contamination of dirty wounds or in illicit injecting drug use (see image).
- Iatrogenic botulism may occur due to accidental injection into the blood stream of commercial botulinum toxin (for example, Botox®, Dysport® or Xeomin®).
- Inhalational botulism does not occur naturally but would result from breathing in toxin used as a biological weapon.
Image courtesy Public Health Image Library (PHIL), Department of Health and Human Services, Centers for Disease Control and Prevention (CDC-USA)
Signs and symptoms
Symptoms may include:
- vertigo (dizziness)
- blurred vision
- dry mouth
- difficulty swallowing
- difficulty speaking
- paralysis of the muscles which move the eyes
- drooping eyelids
One to ten percent of persons with botulism die as a result.
As well as the symptoms listed above, symptoms of foodborne botulism may include:
- abdominal cramping
In infants the following symptoms may occur:
- poor suck
- altered cry
- poor head control (see image)
The diagnosis is made from the history and signs and symptoms of infection (clinical features).
Diagnosis can be confirmed by detection of toxin in clinical specimens such as faeces or blood.
In foodborne botulism, toxin may be detected in the contaminated food item.
(time between becoming infected and developing symptoms)
- Foodborne botulism: usually 12 to 36 hours, but sometimes several days.
- Infant botulism: unknown.
- Intestinal botulism: unknown.
- Wound botulism: up to 14 days.
- Inhalational botulism: probably between 12 hours and 3 days.
(time during which an infected person can infect others)
Botulism is not spread from person to person.
An anti-toxin is available.
In infant botulism, botulism immune globulin can be used (BabyBIG®).
In non-fatal cases, recovery may be prolonged.
Exclusion from childcare, preschool, school and work is not necessary.
- ensure safe home and commercial canning and bottling by:
- using good quality and fresh produce
- ensuring foods are sufficiently acidic either naturally or by addition of acid (for example, lemon juice, citric acid or vinegar)
- ensuring foods are properly heat processed
- using appropriate equipment
- ensure proper processes in the making of fermented foods
- follow the manufacturer’s instructions for food storage and shelf life
- avoid consuming foods from damaged cans or bottles
- keep cold food below 5°C and hot food above 60°C.
- avoid feeding honey to infants less than 12 months of age.
- clean thoroughly any dirty wounds and seek medical care
- avoid illicit injecting drug use
- use only licenced products and follow the manufacturer’s instructions.
- Hand hygiene
- Keeping areas clean
- Preventing food poisoning at home
- Shopping and storing of food at home
- Collecting a faecal sample
- When you have a notifiable condition
1 – In South Australia the law requires doctors and laboratories to report some infections or diseases to SA Health. These infections or diseases are commonly referred to as ‘notifiable conditions’.
Image 1 and 2 – Image courtesy of Public Health Image Library (PHIL), Department of Health and Human Services, Centers for Disease Control and Prevention (CDC-USA)
Botulism: What You Don’t See or Smell Can Still Hurt You
Botulism is the name of the food poisoning we get by consuming the toxin of bacteria Clostridium botulinium. Botulism is a rare but serious foodborne disease that can be fatal. There are two different types of botulism poisoning associated with foods—adult and infant botulism.
Where does botulism come from?
The bacteria, Clostridium botulinum, grow anaerobically, meaning they grow in the absence of air—in places like home-canned products and in the intestines of animals and humans. The bacteria produce spores that are very resistant to heat and chemicals, and under the right environmental conditions, can transform into an active bacteria. The spores can be found in soil all over the world and can contaminate vegetables in the field and other natural foods such as syrup and honey. The toxin that Clostridium botulinum produces is among the most deadly food toxin known. Fortunately, heat destroys the toxin and cooking is the best way to control botulism.
Symptoms of illness
The symptoms of botulism depend upon the age of the person exposed. In adults this may include difficulty in swallowing, speech, and breathing, and double vision. The onset of botulism is usually 18 to 36 hours after eating the contaminated food, although it can be as soon as four hours and as long as eight days. In infants, signs of botulism include constipation, muscle weakness, and loss of head control, also called “the floppy baby.”
Public health consequences
The exact number of botulism cases that occur each year is hard to determine because the local Health Department and Centers for Disease Control and Prevention (CDC) cannot record the number of cases accurately unless the ill person seeks medical care, which is unusual in mild cases. The CDC has calculated an estimate of the number of cases of botulism based on corrections for underreporting or misdiagnosis. The CDC estimates that there are 55 cases of botulism each year in this country, and that 100% of the cases are caused by eating food contaminated with the toxin produced by the bacteria. About 42 cases will be severe enough to require hospitalization; 9 deaths are possible each year.
Anyone can become ill by eating food that has been improperly stored. Some will have more severe symptoms depending on the dose of toxin that they consume. Infants are particularly at risk.
How can botulism be prevented?
There are very few cases of botulism each year. The death rate is high if not treated immediately. Prevention is extremely important. Botulism spores can produce the toxin if mistakes are made in home canning food. Home canning should follow strict instructions and hygienic recommendations to reduce risks. Pressure canners should be used for all foods that are naturally low in acid. The botulism spores can only be killed by the high heat that can be obtained in a pressure canner. In addition, home-canned foods should be boiled for 20 minutes before tasting or eating.
Are home-canned foods the only concern?
Infant botulism is a concern for children under one year of age. It is possible for bees to pick up the botulism spores from flowers or soil. These spores are not destroyed during the processing for honey. The botulism spores grow in the baby’s intestinal tract and then produce the toxin. This is less likely to occur after the age of one year when the baby’s digestive tract matures.
Flavored oils also can be a concern if not prepared correctly. When herbs, garlic, or tomatoes are placed in oils, the botulism spores on the plant material can start to produce the toxin in this anaerobic mixture. To be safe, keep these flavored oils refrigerated and make only the amount of herbal oils and butters that will be used in a few days. Using dried herbs and vegetables will also reduce the risk.
Baked potatoes wrapped in foil and kept at room temperature occasionally form the anaerobic conditions the botulism spores need to produce their toxin. For this reason, leftover potatoes should be refrigerated. Potato salad made from leftover baked potatoes that have been improperly refrigerated has been implicated in botulism poisoning.
How can I control the pathogen in my home?
- Boil all home-canned, low-acid foods 20 minutes before eating. Low-acid foods are most vegetables, some tomatoes, and meat or poultry.
- Discard all raw or canned food that shows any sign of being spoiled.
- Discard all bulging or swollen cans of food and food from glass jars with bulging lids.
- DO NOT TASTE food from swollen containers or food that is foamy or has a bad odor.
- Process low-acid foods at temperatures above boiling (which can only occur using a pressure canner) and for the recommended time for the size of can or jar you are using.
- Can low-acid foods in a pressure canner. Do not can low-acid foods in the oven, in a water-bath canner, open kettle, or vegetable cooker.
- If you suspect that home-canned food has spoiled, heat the food to boiling to destroy possible toxin, then discard the food. Do not eat this food. Clean all surfaces with chlorine/water solution (one tablespoon of bleach per gallon of water) that leaky containers may have contaminated. Then boil any sponges or cloths used for clean-up to destroy the toxin. Then, discard the sponges or clean-up cloths.
- Do not give honey or foods with honey to infants under one year of age.
There are a number of organisms that can make people sick. It is not possible to determine which pathogen is causing the problem based on symptoms alone. Individuals suffering from serious illness should seek appropriate medical advice.
Centers for Disease Control and Prevention. Botulism. cdc.gov/botulism/. Accessed: August 22, 2011. Scallan, E., Hoekstra, R.M., Angulo, F.J., Tauxe, R.V., Widdowson, M.A., Roy, S.L., Jones, J.L., & Griffin, P.M. Foodborne illness acquired in the United States—major pathogens. Emerging Infectious Diseases 2011; 17:7–15. U.S. Food and Drug Administration. Clostridium botulinum. The Bad Bug Book. www.fda.gov/Food/FoodborneIllnessContaminants/CausesOfIllnessBadBugBook/ucm296005.htm. Accessed: August 22, 2011.
For more information about food safety, visit Foodsafety.osu.edu.