Botulism

Botulism is type of poisoning caused by the botulinum nerve toxin, also known as the botulinum neurotoxin. 

The botulin nerve toxin is primarily produced by a type of bacteria called Clostridium botulinum. The bacteria and their spores are common in nature – they can be found in soil and bodies of water. If the spores germinate, the bacteria grow and excrete toxins.

Botulinum neurotoxin is one of the most powerful toxins that’s ever been known. Even tiny amounts can be fatal. 

Forms of botulism

There are six forms of botulism:

• Food-borne botulism: this is the most common form and results from the consumption of food populated with clostridia.
• Wound botulism: this form mostly happens when the bacteria’s spores get into a wound, where they then germinate.
• Infant botulism: this can affect infants under one year of age because their stomach is not yet as acidic as an adult’s and their intestinal flora is not yet fully developed. Infant botulism has often been linked to eating honey.
• Inhalation botulism: this can affect laboratory workers.
• Iatrogenic botulism: this form of poisoning results from too much toxin being accidentally or incorrectly injected for medical reasons or during a cosmetic procedure (“Botox”).
• Rare and special forms: in combination with pre-existing intestinal conditions, the bacteria can also affect adults’ intestines.

Infection figures in Germany

Botulism is a notifiable condition in Germany. An average of 5 people contract botulism each year. Botulism cannot be transmitted from one person to another.

The symptoms of botulism depend on how much botulinum nerve toxin has got into the body and how long it has been taking effect.
The typical symptoms of botulin nerve toxin poisoning include the following:

• Dry mouth
• Nausea, vomiting, diarrhea
• Dilated pupils
• Signs of paralysis of the eye muscles: impaired near vision, double vision
• Paralysis of the pharyngeal (throat) muscles: swallowing problems, dysphonia (for example hoarseness), speech problems
• Paralysis of the muscles with associated weakness of the limbs and neck; in the more advanced stages, general debility
• Paralysis of the respiratory muscles with life-threatening breathing difficulty
• The pharyngeal muscles being affected means that the protective cough reflex may not work properly. Stomach contents can get into the lungs and cause pneumonia.
• If the paralysis reaches the intestinal muscles, this can cause constipation and even bowel obstruction.

Symptoms of wound and infant botulism

• The wound infection in wound botulism can result in fever.
• In addition to symptoms such as shortness of breath, constipation, swallowing problems and sucking weakness, infant botulism also leads to general muscle weakness, flaccid paralysis and to a physical developmental delay.

Botulism is caused by the botulinum nerve toxin (botulinum neurotoxin). 

The toxin is a metabolic product from bacteria of the genus Clostridium. It is mainly produced by the bacterium Clostridium botulinum. 

Clostridia grow in anaerobic conditions, i.e. in environments without oxygen. As such, canned, preserved and air-tightly sealed foods are frequent sources. Clostridia produce spores that germinate in the absence of oxygen and develop into poisonous bacteria.

Clostridia and their spores are common worldwide and found in soil, bodies of water and agricultural products. 

The spores are highly resistant. They can survive in this development stage for a long time and still germinate years later.

Everyone is at risk of being affected by botulism if clostridia get into their gastrointestinal tract or bloodstream 

but some people are at higher risk than others:

• Babies under 12 months do not have the acidic environment in their stomachs that adults have to kill off the clostridia and their spores. Honey can contain spores that germinate in young children’s intestines and cause infant botulism.
• Drug users can get wound botulism from injecting under their skin.
• People who slaughter their own animals: home-made preserved sausage products cause the vast majority of cases of poisoning with botulinum nerve toxin in Germany.

There is no approved vaccine against the botulinum neurotoxin. The most important preventative measure is ensuring good food hygiene. 

Current food and hygiene regulations mean that the risk of being poisoned by industrially produced products is extremely low in Germany.

Most cases of botulism in Germany result from home-made and home-preserved food populated by clostridia or their spores. 

To avoid botulism, it is important to properly produce, process and store food. This particularly includes cooking dishes for long enough to sufficiently heat them all the way through. This is the only way to kill off the spores. Freezing, on the other hand, will not do this. 

When warming meals, it is important to heat them at a temperature of over 85 degrees for several minutes.

More information on preventing food-borne botulism can be found in the consumer brochure published by the Federal Institute for Risk Assessment (Bundesinstitut für Risikobewertung – BfR) (in German only).

The symptoms of botulism are initially non-specific. This makes it difficult to make an early diagnosis. Early symptoms such as a dry mouth and gastrointestinal problems can also be caused by other forms of poisoning and infection. In the event of paralysis, other neurological disorders have to be ruled out. If several people who ate the same thing have developed symptoms of botulism, this is a strong indication of the condition.

To confirm suspected cases of botulism, blood samples must be sent to a specially equipped laboratory as quickly as possible.
Food-borne botulism can no longer be detected in the blood after 48 hours. If food is a possible cause, meal leftovers can be tested for traces of the toxin. 

Further tests

In addition to blood samples and meal leftovers, doctors also test the following:

• stomach contents/vomit
• stool: for infant and food-borne botulism
• wound swabs: for wound botulism
• contents obtained from bronchial washing: for inhalation botulism
• swab of the inner lining of the nose: for inhalation botulism

Even in suspected cases of botulism, doctors will send patients to hospital so they can be monitored and treated in intensive care.

The paralysis caused by the toxin can spread and affect the respiratory muscles. If left untreated, respiratory paralysis can be fatal. Botulism is therefore always an emergency.

Treatment with antitoxin

Patients are administered an antitoxin in hospital. This must be done quickly. In most cases, doctors therefore administer the antitoxin without waiting for the laboratory results. 

This is because the botulin nerve toxin acts inside the nerve cells, where it stops the neurotransmitter acetylcholine, which sends signals from nerve cells to muscle cells, from being released. 

The antitoxin can only render harmless the botulin nerve toxin still found in the bloodstream. Once the toxin has got into the nerve cells, the antitoxin can no longer take effect. 

Other treatment measures

• Gastric lavage, a procedure that flushes out unbound toxin. This is only appropriate up to a maximum of 2 hours after the toxin has been ingested.
• The doctor may give laxatives or activated charcoal as long as the intestinal muscles have not yet been affected.
• If the intestinal muscles are paralyzed or in case of continuing constipation, patients are given remedies to encourage bowel movement.
• Cholinesterase inhibitors stop the small amounts of messenger substance still being released in the body from being broken down.
• With wound botulism, antibiotics kill off bacteria still present in the body. However, the destroyed bacterial cells still contain toxin, which they can release. This is why an antitoxin is always administered at the same time as the antibiotic.

The toxin that has already been absorbed can remain in the nerve cells for a long time: It can take months for the signaling between nerve cells and muscle cells to be fully restored. Permanent damage does not usually occur.