What happens in botulism, exactly?

What is it?

Botulism is a life-threatening  illness caused by a toxin produced by the bacterium Clostridium botulinium.

Symptoms of botulism appear within hours to a few days of infection. The disease causes muscle weakness, and eventually paralysis that spreads throughout the body from the top down. Initial symptoms manifest themselves through a number of problems, including difficulty seeing, eating, talking, and breathing. In some people the disease also begins with nausea, vomiting, and stomach cramps.

Botulism is quite rare, with an average of 110 cases reported yearly in the US.

What causes it?

Botulism is caused by an infection of the bacterium Clostridium botulinium. The symptoms are a result of the toxin these bacteria excrete. This toxin is one of the most lethal substances known, an inhaling just one microgram of it is enough to kill a man.

In the most common form of botulism, infants are colonized with the bacterium in the small intestine. This can happen through ingesting a variety of improperly prepared food, but with honey perhaps being the most significant single factor. The bacterium can also sometimes be acquired through a wound or the airways.

What happens during it?

Our nerve cells need neurotransmitters in order to communicate with other cells. These small molecules are first released by one neuron after an impulse has traveled through it, and they then attach to a second neuron, causing it to fire an impulse. Acetylcholine is a neurotransmitter with a particularly important role in activating muscles. When the brain decides that a muscle should contract, it sends an electrical signal through nerve pathways, and the last neuron in the chain releases acetylcholine to the muscle cell. This starts a chemical chain reaction, which eventually leads to protein filaments inside the cell sliding between one another and the cell contracting.

The toxin blocks the release of acetylcholine. Even if the brain sends orders to muscles, they can’t get through. This can be very dangerous if the toxin spreads to the neurons that, for example, control breathing.

How can it be treated?

Botulism is generally treated with antitoxin and supportive care. In cases of paralysis, it is vital to help the patient breathe for the 2-8 weeks or so it takes new neural connections to form. Also antitoxin can be injected in the blood, which blocks the action of the toxin. Antitoxin can’t reverse paralysis, though. Botulism is fatal to 5-10% of people who are affected, but if it is left untreated, the number increases to 40-50%.



Sources: https://en.wikipedia.org/wiki/Botulism, http://www.nhs.uk/conditions/Botulism/Pages/Introduction.aspx, http://www.medscape.com/viewarticle/574270_4, https://en.wikipedia.org/wiki/Botulinum_toxin, 




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