Botulism Health Article

Definition

Botulism is a neuroparalytic disease caused by the potent toxin of the Clostridium botulinum bacterium. There are three main types of botulism: foodborne botulism, infant botulism, and wound botulism.

Description

Botulism was first identified in Wildbad, Germany, in 1793, when six people died after consuming a locally produced blood sausage. In 1829, Jutinius Kerner, a health official, described 230 cases of sausage poisoning. Thereafter, the illness became known as "botulism," which is derived from the Latin "botulus," meaning sausage. In 1897, E. Van Ermengem identified the bacterium and its toxin while investigating an outbreak of the disease among musicians in Elezells, Belgium.

C. botulinum is a spore-forming, anaerobic, grampositive bacilli found globally in soil and honey. The toxin has recently gain notoriety. It is a potential bioterrorism agent, and it is used as a beauty aid to eliminate frown lines.

Clinically, food-borne botulism is dominated by neurological symptoms, including dry mouth, blurred vision and diplopia, caused by the blockade of neuromuscular junctions.

In wound botulism the neurologic findings are similar to the food-borne illness, but the gastrointestinal symptoms are absent. Infants suffering from the intestinal colonization of spores of C. botulinum suffer first from constipation, and later develop neurological paralysis, which can lead to respiratory distress.

There are seven distinct neurotoxic serotypes, all of which are closely related to the tetanus toxin. Types A and B are most commonly implicated, but types E and, more rarely, F have been associated with human disease.

Demographics

Botulism is rare, but its incidence does vary by geographic region. The food-borne version remains highest among people who can their own foods. In 1995, only 24 cases of food-borne botulism were reported to the Centers for Disease Control and Prevention.

About 90% of global cases of infant botulism are diagnosed in the US, where the annual incidence is about 2 per 100,000 live births. It is the most common form of human botulism in the United States, with over 1,400 cases diagnosed between 1976 and 1996.

Between 1943 and 1985, 33 cases of wound botulism were diagnosed in the United States, mainly associated with deep and avascular wounds. However, between 1986 and 1996, 78 cases of wound botulism were diagnosed, many the result of illicit drug use, occurring at injection sites or at nasal or sinus sites associated with chronic cocaine snorting.

Causes and symptoms

Botulism is caused by the protein toxin released by the microorganism C. botulinum. After the toxin is absorbed into the bloodstream, it irreversibly binds to the acetylcholine receptors on the motor nerve terminals at neuromuscular junctions. After the toxin is internalized, it cleaves the apparatus in the neuron that is responsible for acetylcholine release, making the neuron unresponsive to action potentials. The blockade is irreversible and may last for months, until new nerve buds grow.

FOOD-BORNE BOTULISM The symptoms can range from mild to life threatening, depending on the toxin dose. Generally, symptoms appear within 36 hours of consuming food containing the toxin. Paralysis is symmetric and descending. The first symptoms to appear include dysphagia, dysarthria, and diplopia, a reflection of cranial nerve involvement. Neck and limb weakness, nausea, vomiting, and dizziness follow. Respiratory muscle paralysis can lead to ventilatory failure and death unless support is provided.

WOUND BOTULISM The in vivo production of toxin by C. botulinum spores, leads to the neurologic symptoms seen in food-borne botulism. Gastrointestinal symptoms are absent.

INFANT BOTULISM Peak incidence occurs between 2 and 3 months of age. C. botulinum spores colonize the gastrointestinal tract and produce the toxin. Most infants show signs of constipation, followed by neuromuscular weakness that results in decreased sucking, lack of muscle tone and characteristic "floppy head." Symptoms may range from mild to severe, and may lead to respiratory failure.

Diagnosis

Physicians should consider a diagnosis of botulism in a patient who presents with neuromuscular impairment, but remains mentally alert. The disease is often mistaken for other more common conditions, including stroke, encephalitis, Guillain-Barré syndrome, myasthenia gravis, tick paralysis, chemical or mushroom poisoning, and adverse reactions to antibiotics or other medication. Sepsis, electrolyte imbalances, Reye syndrome, congenital myopathy, Werdnig-Hoffman disease and Leigh disease should be considered in infants.

A definitive diagnosis can be made by detecting the toxin in serum samples, or isolating C. botulinum from stool or wound specimens. Toxins can be detected with a mouse neutralization assay, or using PCR or ELISA protocols.