Key messages

  • Clostridium botulinum infection (botulism) is an urgent notifiable condition that must be notified immediately to the department by medical practitioners and pathology services. 
  • Botulism is a serious paralytic illness caused by a nerve toxin. Foodborne botulism – the most common form of botulism – is severe and often fatal.
  • Only seven cases of botulism were reported in Australia between 2004 and 2010 – four of these in Victoria.
  • Preventive measures include ensuring effective control of processing and preparation of commercially canned and preserved foods.

Notification requirement for botulism

Clostridium botulinum infection is an ‘urgent’ notifiable condition and must be notified by medical practitioners and pathology services immediately by telephone upon initial diagnosis (presumptive or confirmed). Pathology services must follow up with written notification within 5 days. 

This is a Victorian statutory requirement.

Primary school and children’s services centre exclusion for botulism

Exclusion is not required unless diarrhoea is present, in which case exclusion is required until there has not been a loose bowel motion for 24 hours.

Infectious agent of botulism

C. botulinum is a spore-forming anaerobic bacillus. Several serotypes exist; however, only types A, B, E and (rarely) type F cause human disease.

Identification of botulism

Botulism is a serious paralytic illness caused by a nerve toxin that is produced by C. botulinum.

Clinical features

There are four naturally occurring forms of botulism with similar clinical features.

Foodborne botulism

Foodborne botulism is a severe and often fatal infection resulting from ingestion of food contaminated with the preformed toxin followed by a symmetric, descending flaccid paralysis commencing with the cranial nerves. Symptoms may begin within 6 hours to 10 days (usually within 12–36 hours) and include marked fatigue, weakness and vertigo, usually followed by double vision, blurred vision, dry mouth and difficulty in swallowing and speaking. If untreated, illness may progress to cause descending paralysis; the shoulders are first affected, then the upper arms, lower arms, thighs, calves and so on. Paralysis of breathing muscles can cause loss of breathing and death unless assistance with breathing is provided. There is no fever and no loss of consciousness. Gastrointestinal symptoms, including abdominal pain, nausea, vomiting, constipation and less commonly diarrhoea, may occur.

Infant botulism

Infant botulism is the most common form and usually affects infants under 1 year of age. It occurs when ingested spores germinate in the infant’s intestine, where they reproduce and release the toxin. The illness typically begins with constipation, followed by lethargy, listlessness, poor feeding, diminished suckling and crying ability, drooping eyelids, generalised muscle weakness (‘floppy baby’) and a striking loss of head control.

Adult intestinal botulism

Adult intestinal botulism is similar to infant botulism, although relatively rare. It occurs in immunocompromised adults, those using antibiotics, and those with altered bowel flora due to some anatomical or functional bowel abnormality, such as inflammatory bowel disease. Ingested spores germinate in the intestine and produce bacteria that reproduce in the gut and release the toxin.

Wound botulism

Wound botulism occurs when spores get into an open wound, germinate and produce toxin within 7 days (range 4–21days). These wounds are usually associated with severe trauma, or are needle puncture sites from drug use or nasal or sinus lesions associated with chronic cocaine use.

Iatrogenic botulism

Botulism that does not occur naturally includes iatrogenic botulism arising after inappropriate administration of botulism toxin used for therapeutic purposes.

Diagnosis

Diagnosis of foodborne botulism is made by demonstration of botulinum toxin in serum, gastric aspirate, stool, implicated food or tissue derived from the wound or by culture of C. botulinum from gastric aspirate or stool in clinical cases.

Identification of the organism in suspected food is helpful but not diagnostic because botulinum spores are ubiquitous in the environment. The presence of toxin in suspected food is highly significant.

Electromyography may be useful in corroborating the clinical diagnosis.

Incubation period of Clostridium botulinum

Classical botulism occurs within 12–36 hours (sometimes several days) after eating contaminated food. The incubation period for infant botulism is unknown due to difficulty in determining the precise time of ingestion. Shorter incubation periods are associated with more severe disease and higher case-fatality rates.

Public health significance and occurrence of botulism

Botulism is a rare disease occurring worldwide. Sporadic cases, family and general outbreaks occur where food is prepared or preserved by methods that do not destroy spores and permit toxin formation. Missed diagnoses (particularly for intestinal botulism) are likely, however, due to low clinical suspicion and limited laboratory diagnostic capacity in many areas.

Only seven cases of botulism were reported in Australia between 2004 and 2010. Four occurred in Victoria (Communicable Diseases Network Australia – National Notifiable Diseases Surveillance System).

C. botulinum has been identified as a potential bioterrorism agent, delivered through the inhalation of spores.

Reservoir of Clostridium botulinum

C. botulinum is most commonly found in soil and agricultural products. Spores have been found in marine sediments and the intestinal tracts of animals, including fish.

Mode of transmission of Clostridium botulinum

Foodborne botulism is acquired by the ingestion of inadequately cooked food or processed or refrigerated foods in which toxin has formed, particularly canned and alkaline foods. Sources of spores include soil and foods such as honey. Honey has been described in the United States literature as a source of infection, but has never been implicated in Australia and surveys of Australian honey have failed to identify C. botulinum.

Most cases of wound botulism are due to ground-in soil or gravel. Several cases have been reported among drug users.

Infant botulism arises from the ingestion of spores that germinate in the colon, rather than the ingestion of preformed toxin.

Period of communicability of botulism

Botulism is not spread from one person to another.

Susceptibility and resistance to botulism

Everyone is susceptible to infection, and the reoccurrence of disease has been reported.

Control measures for botulism

Preventive measures

Ensure effective control of processing and preparation of commercially canned and preserved foods.

Educate people undertaking home canning and other food preservation techniques about cooking time, pressure, temperature, adequate refrigeration and storage. This includes the processing of smoked, salted and other preserved meats, fruits, jams and vegetables. For tinned food, the absence of a bulging lid does not preclude C. botulinum contamination.

Control of case

Botulism is a medical emergency. The respiratory failure and paralysis that occurs with severe botulism may require a patient to be on a breathing machine (ventilator) for weeks to months, plus intensive medical and nursing care.

Suspected cases should immediately be referred for specialist care and heptavalent botulinum antitoxin (types A–G) administered as soon as possible. Antitoxin is available via the Special Access Scheme on (02) 6232 8111.

Antitoxin has been used for infant botulism in Australia. Although there is a risk of anaphylaxis and the cost is substantial, some cases have significant clinical benefit when it is administered early, and use should therefore be considered on a case-by-case basis.

Medical staff may try to remove contaminated food still in the gut by inducing vomiting or using enemas.

Human-derived botulism immune globulin (Baby BIG) is used for the treatment of infant botulism caused by C. botulinum type A or type B.

For wound botulism, in addition to the administration of antitoxin, the wound should be debrided and/or drained and appropriate antibiotic prophylaxis against other potential infections should be administered. Antibiotics do not improve the course of the disease and should only be used to treat secondary infections.

Isolation or quarantine is not needed, but handwashing is indicated after handling soiled nappies. Usual sanitary disposal of faeces from infant cases is acceptable. Medical staff caring for patients with suspected botulism should use standard precautions.

Any implicated food should be retained for collection and investigation by public health authorities. Contaminated utensils should be cleaned by boiling or with household bleach.

Control of contacts

Those who have eaten suspect food should be purged with emetics, gastric lavage or enemas. The administration of polyvalent antitoxin to asymptomatic individuals should be considered carefully, assessing potential protection against the risk of sensitisation and severe reactions to horse serum.

Control of environment

Environmental health officers and food safety officers should coordinate the appropriate disposal of implicated food.

Outbreak measures for botulism

An outbreak of botulism is defined as one or more cases of disease. The immediate aim is to identify possible sources of the disease and other people possibly exposed. Recall any implicated food immediately and send samples to the Microbiological Diagnostic Unit for analysis. Take sera, gastric aspirates and stool specimens from cases as well as from those exposed but asymptomatic (before the administration of antitoxin) and forward them immediately to the Microbiological Diagnostic Unit for analysis.

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