Botulism

How botulism works

Clostridium botulinum lives as hardy spores in soil and dust. The spores are harmless until they find conditions with no oxygen, low acidity, low salt or sugar, and warmth, such as a poorly processed sealed jar. They then germinate and make toxin.

Botulinum toxin is one of the most potent toxins known. It enters nerve endings and stops the release of acetylcholine, the chemical that tells muscles to contract. The result is flaccid (floppy) paralysis. Recovery requires nerve endings to grow new connections, which takes weeks to months.

Botulism does not spread from person to person.

Types of botulism

Infant botulism is the most common form in the US.

Symptoms

In adults and older children

Early symptoms involve the cranial nerves:

• double vision or blurred vision
• drooping eyelids
• slurred speech and a hoarse or weak voice
• difficulty swallowing
• dry mouth
• facial weakness

These are followed by symmetric, descending weakness: neck, arms, breathing muscles, trunk and legs. Breathing failure (respiratory failure) is the main danger.

Other features:

• no fever (unless a wound is infected)
• normal alertness and sensation
• large or sluggish pupils
• constipation and urinary retention
• in foodborne cases, nausea, vomiting or diarrhea may come first

In babies

• constipation, often the first sign
• poor feeding, weak suck
• weak cry
• floppiness ("floppy baby")
• reduced facial expression and drooping eyelids
• drooling
• breathing difficulty in severe cases

How botulism differs from similar conditions

Diagnosis

Botulism is diagnosed clinically, and treatment starts immediately without waiting for test results.

• Notify public health: in the US, doctors contact their state health department, which consults the CDC 24/7 and releases antitoxin.
• Laboratory tests: blood, stool, vomit, wound and food samples are tested for toxin or bacteria at public health laboratories. Results take days.
• Nerve conduction studies and electromyography support the diagnosis.
• Tests to exclude other conditions, such as a brain scan or spinal fluid analysis.

Treatment

Antitoxin

• Adults and children over 1 year: heptavalent botulinum antitoxin, supplied in the US by the CDC through health departments. It neutralizes toxin still circulating but cannot reverse paralysis already present, so it works best when given early.
• Infants: human-derived botulism immune globulin (BabyBIG), which shortens hospital stays.

Supportive care

• Intensive care monitoring of breathing; many patients need a ventilator, sometimes for weeks.
• Feeding through a tube while swallowing is impaired.
• Prevention of complications such as pneumonia, blood clots and pressure sores.
• Rehabilitation with physical, occupational and speech therapy.

Wound botulism

Antitoxin plus surgical cleaning of the wound and antibiotics. Antibiotics are not used for infant botulism because killing the bacteria may release more toxin.

Outlook

With antitoxin and modern intensive care, the death rate in the US is now under about 5%. Recovery can take weeks to months. Some people have fatigue and shortness of breath for a year or longer.

Prevention

Home canning and food safety

• Use a pressure canner for low-acid foods such as vegetables, meat, fish and beans, following tested recipes from the USDA or similar. Boiling-water canning is not enough for these foods.
• Discard bulging, leaking or cracked cans and jars, or food that spurts or smells off. Never taste it.
• Refrigerate homemade oils infused with garlic or herbs and use within 4 days.
• Keep baked potatoes wrapped in foil hot or refrigerate them promptly.
• Boiling home-canned low-acid food for 10 minutes before eating destroys the toxin, though not spores.

Infants

Never give honey to babies under 12 months, including in baked goods or on pacifiers.

Wounds and injections

Avoid injecting street drugs; seek care for injection-site infections. Use botulinum toxin injections only from licensed providers.

Frequently asked questions

What are the first symptoms of botulism?

The first symptoms usually affect the face and eyes: double or blurred vision, drooping eyelids, slurred speech, difficulty swallowing and dry mouth. Weakness then spreads down to the arms, breathing muscles and legs. In babies, constipation, poor feeding and a weak cry often come first.

How long does it take for botulism symptoms to appear?

Foodborne botulism symptoms usually begin 12 to 36 hours after eating contaminated food, but can appear from 6 hours to 10 days. Wound botulism takes around 4 to 14 days. Infant botulism can develop 3 to 30 days after swallowing spores.

Why can't babies have honey?

Honey can contain botulism spores. A baby's gut is not mature enough to stop the spores growing and making toxin, which can cause infant botulism. After 12 months, the gut bacteria protect against this, so honey becomes safe.

Can you survive botulism?

Yes. With prompt antitoxin and intensive care, most people survive, and the US death rate is now under about 5%. Recovery can take weeks to months because nerve endings must regrow. Some people have lingering fatigue and breathlessness.

How do I know if canned food has botulism?

You often cannot tell, because food with toxin may look and smell normal. Warning signs include bulging, leaking or dented cans, cracked jars, loose lids, liquid spurting when opened, or a bad smell. Throw these away without tasting, and follow tested pressure-canning methods for low-acid foods.