Botulism

Overview

Botulism is a rare neuroparalytic disease that can be life-threatening. Clostridium botulinum is a gram-positive spore-forming bacterium that is present in the environment and produces toxins under specific conditions. The disease is caused by neurotoxins produced by the bacterium.

Botulinum toxins are a group of 8 related neurotoxins (Types A-H), produced by C.botulinum. Most cases of human botulism are caused by toxin types A, B, E, and rarely F, G, and H. Worldwide, cases consist mostly of infant botulism, foodborne botulism, and wound botulism. Rarely, botulism may be iatrogenic.

Pathogen(s)

Clostridium botulinum.

Transmission

There are various modes of transmission:

• Food-borne botulism occurs via the ingestion of pre-formed toxins in contaminated food, usually from home-canned foods (e.g. fruits, vegetables, fish)

• Infant botulism results from ingestion of botulinum spores rather than pre-formed toxin. Sources of spores include environmental dust/soil and contaminated food (e.g. honey)

• Wound botulism occurs via the introduction of botulinum spores into wounds, especially among injection drug users

• Inhalational botulism can occur if botulinum toxins are inhaled when released in the form of an aerosol (e.g. bioterrorism)

• Iatrogenic botulism can be caused by cosmetic use of botulinum toxin administered as an unlicensed, highly concentrated preparation

There is no human-to-human transmission.

Incubation period:

• Food-borne botulism: Typically 12 to 72 hours after ingestion of toxin, range is 2 hours to 10 days

• Infant botulism: spores may take up to 30 days (average 2 to 4 weeks) to germinate and colonise the infant gut, before the onset of symptoms

• Wound botulism: Typically 4 to 14 days

• Inhalational botulism: Symptoms may appear 12 to 36 hours or longer after exposure

Clinical features

Symptoms may include visual impairment, speaking, swallowing and breathing difficulty and lethargy. In severe cases, one’s diaphragm and chest muscles get affected, and it will be difficult for someone to breathe properly, resulting in death.

Gastrointestinal symptoms may include vomiting, nausea, abdominal pain, diarrhoea, or constipation.

In infant botulism, onset can be insidious, and constipation is a prominent feature. Constipation may precede weakness by weeks. Infants may develop irritability with a weak cry and loss of head control/truncal tone. In infants, dysphagia, poor feeding, poor gag, and pooling of oral secretions often precede respiratory distress.

Risk factors

• Individuals who consume improperly canned (whether home-canned or commercially canned), preserved, or fermented foods such as low-acid vegetables (including green beans, spinach, mushrooms, and beets), fish (including canned tuna, fermented, salted, or smoked fish) or meat products (including ham and sausage) are at risk of botulism poisoning.

• Infants younger than 1 year who are fed honey, are at increased risk of infant botulism.

• Persons who use injection drugs are at increased risk of wound botulism

• Persons who receive very high dose of botulinum toxin for cosmetic purposes may be at increased risk of iatrogenic botulism.

Diagnosis

Diagnosis is primarily based on a compatible clinical presentation. The index of suspicion should be high in afebrile infants who present with significant hypotonia with cranial nerve signs after a period of normal growth and development. Laboratory confirmation is done by culture, polymerase chain reaction (PCR) or demonstrating the presence of botulinum toxin in serum, stool or wound.

Treatment and management

Treatment of botulism involves botulinum antitoxin and supportive care, including prompt intubation and ventilation if necessary. For wound botulism, antibiotics may be used in addition to appropriate debridement of wounds.

Precaution, prevention, and control

Foodborne botulism can be prevented by:

• Avoiding tasting or eating foods from containers that are leaking, have bulges or are swollen, look damaged or cracked, or abnormal in appearance. Do not use products that spurt liquid or foam when container is opened

• Keeping opened canned food out of the temperature danger zone (5°C to 60°C) if you are not serving or eating them soon. Refrigerate the food immediately or keep it warm at 60°C or higher

• Ensuring raw and cooked food are kept apart to prevent cross-contamination. Discard all swollen, gassy, or spoiled canned foods. Double bag the cans or jars with plastic bags and seal them tightly. Keep it out of the reach of humans and pets

• Boiling home-canned food for at least 10 minutes before eating

Wound botulism can be prevented by keeping wounds clean. Persons should seek medical care quickly if the wounds appear infected.

Infants should not be fed honey to reduce risk of infant botulism.

To prevent iatrogenic botulism, use only Health Sciences Authority (HSA)-approved botulinum toxin products administered by qualified medical professionals.

Notification

Who should notify:

• Medical practitioners

• Laboratories

When to notify:

• On clinical suspicion/ laboratory confirmation

How to notify:

• Please refer to the Infectious Disease Notification for more information.

Notification timeline:

• As soon as possible. No later than 24 hours from the time of diagnosis/ laboratory confirmation.

Resources

Please refer to the Weekly Infectious Diseases Bulletin for the number of confirmed botulism cases in Singapore.