Botulism in humans: symptoms, diagnosis and treatment

Botulism is a serious condition that can affect both humans and animals. Contact with as little as 15 nanograms of botulinum toxin can be fatal. This makes it the most toxic substance in the world. As a human being you can become infected by eating spoiled food, swimming in contaminated water or through contact with chemical weapons. Fish and waterfowl regularly die from botulism because water in lakes and ponds has become contaminated with it.


  • What is botulism?
  • Botulism and symptoms in humans
  • Course of the condition
  • Infantile botulism
  • Treatment of botulism in humans
  • Diagnosis often wrong
  • Possible antidote against botulism discovered

What is botulism?

Botulism is a condition that you can get by coming into contact with the poison botulinum or botulinum toxin . There are seven types of poison (A to G). Of these, three are dangerous to humans (A, B and E and in very rare cases F). Under certain circumstances, the substance can multiply very quickly, creating the risk of a major outbreak. This happens, for example, in oxygen-poor but protein-rich environments and in water with a temperature higher than 20 degrees Celsius. However, humans mainly develop the condition after consuming contaminated food. It can occur in foods where any spores of the bacterium Clostridium botulinum are not killed during the production process and are subsequently not heated sufficiently before consumption. It can occur in foods that are not too acidic (a pH above 4.6). You can think of smoked fish, lobster, tuna, ham, chicken liver, mushrooms, spinach, asparagus, beans, soups, corn, olives and pepper.

If you come into contact with the toxin secreted by botulinum, this can lead to a blockage in the transmission of signals between nerves and muscles. This can cause muscle paralysis. Because it also affects the lungs and heart, it can lead to death. Only a small dose is required for this. Botulism is quite rare. In recent years, only six countries report 10 or more infections per year. These were all European countries. In the Netherlands, hospitals have a duty to report the disease.

There are four forms of botulism:

  • Food botulism (primary food poisoning)
  • Infant botulism
  • Wound botulism
  • A form that has not yet been classified

Botulism and symptoms in humans

The most common form in humans is food botulism. If you have come into contact with botulinum, it sometimes takes a few days before the symptoms become visible. The first complaints may occur after 10 to 20 hours. After inhalation of aerosolized botulinum toxin, the incubation period may be even shorter. This concerns the following complaints:

  • Dry mouth and throat
  • (Severe) diarrhea
  • Nausea with vomiting
  • Increasing flaccid paralysis
  • Shortness of breath
  • Drooping eyelids
  • Double vision (diplopia)
  • Speech disorders (dysarthria)
  • Voice disorder (dysphonia)
  • Swallowing disorder (dysphagia)
  • Stalling of the intestines (constipation)

Course of the condition

Most characteristically, the paralysis often starts in the face because it affects the cranial nerve. This controls a group of twelve nerves that influence eye movements, the muscles in the face and the muscles that make chewing and swallowing possible. External features consistent with incipient paralysis of the cranial nerve are: drooping eyelids, double vision, difficulty swallowing, loss of facial expression and speech problems.

The next body parts affected are the arms and legs (starting at the shoulders and thighs and moving downwards). Paralysis of the muscle groups involved in breathing can cause problems with gas exchange. This results in shortness of breath and in severe cases, the build-up of carbon dioxide that will lead to coma and ultimately death.

In addition to the somatic nervous system (also called voluntary nervous system), the visceral or autonomic nervous system is also affected. This can lead to xerostomia (dry mouth and throat due to lack of saliva), orthostatic hypotension (sudden drop in blood pressure) and constipation (blockage of the intestines).

Infantile botulism

Botulism in humans is actually most common in small children. In the United States, this diagnosis is made about a hundred times a year. It mainly occurs in infants under six months of age. The cause is ingestion of spores of the bacterium Clostridium botulinum . This is mainly found in natural products such as honey . This is harmless to adults, but the spores can develop into full-fledged bacteria in the gastrointestinal tract of babies. For this reason it is not recommended to give honey to babies.

Treatment of botulism in humans

Anyone who has contracted botulism must be admitted to a hospital. In the absence of a fully effective drug, a combination of different treatments is used. First of all, an attempt will be made to remove any bacteria still present in the body. This can be done by inducing vomiting and using an enema or enema. Subsequently, it is important to relax while monitoring whether the fluid balance and the absorption of nutrients remain in order. Two methods can be used to combat the disease in food botulism. The bacteria are sensitive to benzylpenicillin and metronidazole. However, treatment with antibiotics is controversial because it can release additional toxins that can worsen the condition. Antitoxin is not used for infant botulism.

Diagnosis often wrong

Because the condition is quite rare, it is often misdiagnosed. People often think of autoimmune diseases or exposure to toxic gases. Diagnoses that are made include:

  • Polyradiculoneuropathy (Guillain-BarrĂ© or Miller-Fisher syndrome)
  • Myasthenia gravis
  • Tick paralysis / Lyme disease
  • Infection of the central nervous system
  • Stroke / Cerebrovascular accident (CVA)
  • Poisoning with carbon monoxide, nerve gas, organic phosphates, mushrooms or alcohol

Possible antidote against botulism discovered

Scientists from Utrecht University have succeeded in mapping the properties of botulinum toxin even better. This enabled them to develop a substance that prevents nerve cells from absorbing the poison. It therefore cannot have a harmful effect on the body. This discovery also opens the doors for research into developing a drug that people can use preventively against botulinum toxin in chemical weapons. The scientists published about this in 2013 in the leading American journal Nature .