Botulism

Botulism is a type of poisoning and so cannot be spread from one person to another. In Germany, usually fewer than 10 people get it each year.

Botulism is caused by neurotoxins known as botulinum neurotoxins. Botulinum neurotoxin is one of the most powerful toxins that’s ever been known. The lethal dose is just 0.001 micrograms per kilogram of body weight, meaning the toxin is listed as a bioweapon in the War Weapons List.

The toxin is mainly produced by the genus of bacteria Clostridium botulinum. It is also produced by the Clostridium strains C. baratii, C. butyricum and C. argentinense. The “botulinum” part of the name indicates where the pathogen (germ) can be found. The Latin word “botulus” means sausage. But the bacteria are also common in nature – they can be found in soil and bodies of water. The bacteria germinate (start growing) under low-oxygen conditions and release their toxin.

There are six forms of botulism:

• Food-borne botulism: This is the most common form and happens when a person consumes a food in which Cl. botulinum has been able to grow and produce toxin.
• Wound botulism: This form mostly happens when the botulinum spores get into a wound where they then germinate.
• Infant botulism: This can happen in small children 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: Can happen when laboratory workers breathe in toxic dust.
• Iatrogenic botulism: This form of botulism results from having (accidentally) too much of the Botox toxin injected during a cosmetic or medical procedure.
• Rare and special forms: In combination with pre-existing conditions, the bacteria can also affect the intestines of adults.

The disease does not cause a fever. It manifests itself largely regardless of how the bacteria got into the body. The symptoms are based on how much toxin gets into the body and how long it has been taking effect there.

The typical symptoms of botulism include:

• Dry mouth
• Nausea, vomiting, diarrhea
• Signs of paralysis of the eye muscles: flickering before the eyes, double vision, photophobia
• Paralysis of the pharyngeal (throat) muscles: swallowing problems, dysphonia (for example hoarseness), speech problems
• If your hand becomes paralyzed, this changes your handwriting.
• 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.
• Sometimes patients lose the ability to control the direction in which they move their head.
• They may develop circulatory disorders and generalized weakness.
• If the paralysis reaches the intestinal muscles, this can cause constipation and even bowel obstruction.
• 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 botulinum neurotoxins. These are some of the most potent toxins known. Just 0.001 micrograms of botulinum per kilogram body weight is fatal.

The toxin is a product of the metabolism of bacteria of the genus Clostridium. These rod-shaped bacteria cannot tolerate oxygen and multiply by forming spores, very resistant forms of transmission that can germinate again years later without metabolism.

Clostridia and their spores are common worldwide in soil, bodies of water and agricultural products including honey and meat products. The bacteria produce the toxin under oxygen exclusion (anaerobic conditions) and release it.

The toxin is mainly produced by the bacterium Clostridium (C.) botulinum. Individuals strains of C. baratii, C. butyricum and C. argentinense can also produce the toxins.

Everyone is at risk of being affected by botulism when clostridia get into the gastrointestinal tract or the bloodstream but there are some population groups for whom there is a particular risk.

We know of seven different types of toxin (A-G), with A, B, E and F having been verified as being poisonous to humans. Since it is a toxin, the condition cannot be spread from one person to another.

There is no approved vaccine against the botulinum neurotoxin. But the German food and hygiene regulations prevent the most common form of botulism, food-borne botulism, so effectively that in this country it only occurs once a year, not even that.

In Germany, botulism poisoning is usually caused by home-made food and so it is important to make sure that it is properly manufactured, processed and stored.

The spores of the bacteria are long-lasting and freezing does not kill them off, so meals need to be cooked for long enough to make sure that they are also heated evenly on the inside.

At the start, it is usually difficult to tell whether someone has botulism. This makes it difficult to make an early diagnosis. Its early symptoms can also indicate other types of poisoning, other infections or completely different conditions: signs of paralysis can also indicate a stroke, or tetanus in infants, and gastrointestinal (stomach and bowel) symptoms can also come from other infections or toxins.

So doctors need to rule out other possible conditions when starting treatment. They do this by asking the patient some detailed questions and performing specific physical examinations.

Specially equipped laboratories are able to detect the toxin or bacterium to confirm the suspected botulism. The tests usually deliver results within 48 hours. This is important as the toxin is usually quickly absorbed in the case of food-borne botulism and spreads through the body, making it impossible for it to be detected in the blood afterwards.

If food is a possible cause, meal leftovers can be tested for traces of the toxin. Another good method to use is observing people who have had the same meals as the patient. As well as meal leftovers and samples from the environment, doctors also test the following:

• blood, especially blood serum
• stomach contents/vomit
• stool (for infant and food-borne botulism)
• wound swabs (for wound botulism)
• contents obtained from irrigation (washing out) of the bronchi (for inhalation botulism)
• swab of the inner lining of the nose (for inhalation botulism)

Want to know which tests are carried out to confirm a suspected diagnosis of botulism? You can read more about the testing methods on the Robert Koch Institute Consultant Laboratory website.

As soon as doctors suspect botulism, they arrange for patients to be referred to a hospital where they will receive intensive care and in most cases artificial respiration. 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.

Once they have been admitted, patients are then given an antitoxin, which must be administered quickly, often even before the diagnosis has been confirmed by a laboratory. The reason for this is that the bacterial toxin acts inside the nerve cells, where it stops the neurotransmitter acetylcholine, which sends signals from nerve cells to muscle cells, from being released. Once the toxin has been absorbed into the cells, the antitoxin can no longer reach it, so administering it only stops the condition from spreading further.

The situation is different if patients continue to show signs of constipation or the symptoms of the illness even get worse. That suggests that the toxin is still being absorbed from the intestines.

Other treatment methods that can relieve symptoms are:

• 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 amount of the messenger substance still being released in the body from being broken down.
• With wound botulism, antibiotics kill off bacteria still present in the body. The antibiotic dissolves the bacterial cells and they release the toxin present in them. This is why an antitoxin is always administered at the same time as the antibiotic.

The toxin is absorbed in nerve cells where it can remain for a long time. It can take months until the signaling between nerve cells and muscle cells is fully restored.