Causes of Botulism: An Overview
Botulism is a rare but serious illness that can cause paralysis or death. The cause of botulism is a nerve toxin (botulinum toxin) that is produced by the bacterium Clostridium botulinum.
Causes of Botulism: Clostridium Botulinum Nerve Toxin
Clostridium botulinum is the name of a group of bacteria commonly found in soil and marine sediments worldwide. Their spores are often found on the surfaces of fruits and vegetables, as well as in seafood. These rod-shaped organisms grow best in low-oxygen conditions. The bacteria form spores, which allow them to survive in a dormant state until exposed to conditions that can support their growth.
The bacteria and spores themselves are harmless; the dangerous substance is the toxin the bacteria produce when they grow. These bacteria produce seven types of botulism toxin, designated by the letters A through G. However, only types A, B, E, and F cause botulism in humans. Botulinum toxin is the most poisonous substance known to exist.
Once in the body, the botulinum toxin binds to nerve endings at the point where the nerves join muscles. This prevents the nerves from signaling the muscles to contract. The result is weakness and paralysis that descends from the head down, affecting — among other things — the muscles that control breathing.
Treating Botulism
Treatment of this illness includes:
- Careful observation
- Supportive care
- Administering a botulism antitoxin.
Antibiotics are of little use to treat the symptoms caused by the toxin, but healthcare providers use them to treat wound botulism. Currently, there is no vaccine approved by the U.S. Food and Drug Administration (FDA) for use on botulism. Research on a vaccine, however, is at an advanced stage.
Incubation Period
The time between a person becoming infected with botulism bacteria and the beginning of symptoms is called the “botulism incubation period.” The incubation period varies based on the type. For foodborne botulism, the incubation period is between 18 to 36 hours, but can occur as early as 6 hours or as late as 10 days.
The incubation period for infant botulism is between 3 and 30 days, while the incubation period for wound botulism is around 10 days.
What Are the Symptoms?
The earliest symptoms may include:
- Double vision
- Drooping eyelids
- Slurred speech
- Dry mouth
- Blurred vision
- Difficulty swallowing
- Muscle weakness.
Infants with early symptoms of botulism may:
- Appear lethargic
- Have a weak cry
- Have constipation
- Feed poorly
- Have poor muscle tone (see Pictures of Botulism).
If a healthcare provider cannot identify and treat the illness early, the symptoms progress to paralysis of the:
- Arms
- Legs
- Trunk
- Respiratory system.
People with respiratory symptoms may have to use a ventilator to help them breathe until they recover from the toxin, which normally requires 2 to 8 weeks.
Making a Diagnosis
In order to make a diagnosis, the doctor will ask a number of questions and perform a physical exam looking for signs of the toxin. If the doctor suspects botulism, he or she will send a blood or stool sample to a specialized laboratory for analysis.
Because botulism occurs rarely and the symptoms are similar to those seen in other diseases, diagnosis is difficult and the condition is frequently misdiagnosed.
Other diseases that can appear similar to botulism include:
- Guillain-Barre syndrome
- Stroke
- Lyme disease
- Myasthenia gravis
- Polymyositis.
Treating Botulism
Treatment of this illness includes:
- Careful observation
- Supportive care
- Administering a botulism antitoxin.
Antibiotics are of little use to treat the symptoms caused by the toxin, but healthcare providers use them to treat wound botulism. Currently, there is no vaccine approved by the U.S. Food and Drug Administration (FDA) for use on botulism. Research on a vaccine, however, is at an advanced stage.
Prognosis
Botulism can result in death due to respiratory failure. However, in the past 50 years, the proportion of patients with botulism who die has fallen from about 50 percent to 8 percent. A patient with a severe case may require a breathing machine as well as intensive medical and nursing care for several months. Patients who survive an episode of botulism poisoning may have fatigue and shortness of breath for years, and long-term treatment may be needed to aid recovery.
Statistics on Botulism
In theUnited States, an average of 110 cases of botulism are reported each year. Of these, approximately:
- 25 percent are foodborne botulism
- 72 percent are infant botulism
- 3 percent are wound botulism.
The number of cases of foodborne and infant botulism has changed little in recent years, but wound botulism has increased because of the use of black-tar heroin, especially inCalifornia
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