BOTULISM

Last updated: 07 September 2004

1. Reason for surveillance

• To identify the source of foodborne botulism

• To prevent further cases

• To monitor the epidemiology to inform the development of better prevention strategies.

2. Case definitions

A confirmed case requires laboratory definitive evidence AND clinical evidence.

Laboratory evidence

• Isolation of Clostridium botulinum or

• Detection of C. botulinum toxin in blood or faeces.

Clinical evidence
A clinically compatible illness (eg. diplopia, blurred vision, muscle weakness, paralysis, death).

Epidemiological evidence
Not applicable.

3. Notification criteria and procedure

Foodborne botulism is to be notified by:

• Hospital CEOs on provisional clinical diagnosis (ideal reporting by telephone within 1 hour of diagnosis)

• Laboratories on microbiological or toxicological confirmation (ideal reporting by telephone within 1 hour of diagnosis).

Only confirmed cases should be entered onto NDD.

4. The diseases

Infectious agent
Toxin produced by the spore-forming obligate anaerobic bacillus Clostridium botulinum.

Mode of transmission
Foodborne botulism is transmitted by ingesting toxins produced by C. botulinum. The toxin is commonly found in improperly processed, canned, low acid or alkaline foods where anaerobic conditions have occurred at some stage. Infant botulism is due to the ingestion of spores followed by the production of the toxin in the intestines of infants. Wound botulism can occur from contamination of a wound, generally by infected soil or gravel.

Timeline
The typical incubation period for foodborne botulism can vary from 6 hours to 8 days, but is commonly 12 to 36 hours. Usually the shorter the incubation period, the more severe the disease. Despite excretion of the toxin and organisms in faeces, no evidence of person-to-person transmission has been found.

Clinical presentation
Foodborne botulism is a severe intoxication and presents with marked lassitude, weakness and vertigo, usually followed by double vision, dry mouth and progressive difficulty in speaking and swallowing (cranial nerve involvement) and may progress to descending weakness or flaccid paralysis. The case-fatality rate is up to 10 percent. Infant botulism usually is confined to children <1 year old and typically begins with constipation followed by lethargy, weakness, poor feeding, difficulty swallowing, loss of head control and hypotonia.

Wound botulism, which is rare, presents with a similar picture to foodborne botulism.

5. Managing single notifications

Response times
Investigation
Immediately on notification of a suspected or confirmed case begin follow-up investigation, and notify Communicable Diseases Branch. Follow-up of infant botulism or wound botulism is not required.

Data entry
Within 1 working day of notification enter confirmed case on NDD.

Response procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. Regardless of who does the follow-up, PHU staff should ensure that action has been taken to:

• Confirm the onset date and symptoms of the illness

• Confirm results of relevant pathology tests, or recommend the tests be done

• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview

• Seek the doctor's permission to contact the case or relevant care-giver

• Review case management

• Identify and control likely source.

Case management
Investigation and treatment
The case should be closely monitored to enable respiratory failure to be managed immediately, where necessary.

Confirmation of suspected cases is important. Toxin can be isolated from stool (collect 25 g), and serum. Send samples to ICPMR clearly marked for botulism testing, after calling the Public Health Microbiology Registrar or consultant on call. Samples will generally be forwarded for toxin mouse bio-assay testing. Electromyography is also important in establishing the clinical diagnosis.

Ideally trivalent botulinum antitoxin (ABE) should be given to adult cases as soon as possible and within 24 hours. It is available in Australia from CSL (1800 333 011). ABE should not be given to infants.

Education
The case or relevant care-giver should be informed about the nature of the infection and the mode of transmission. Emphasise the importance of correct food handling procedures, particularly food preservation.

Isolation and restriction
None

Environmental evaluation
The NSW Food Authority should be engaged to collect samples of any suspected residual food for laboratory analysis and provide other advice and action. The method of food contamination should be determined and steps taken to prevent further occurrences if possible.

Consideration should be given to recalling food reasonably suspected to be the source. Recalls should only be initiated by the relevant food authority.

Suspect food and contaminated utensils from cases should be tested, then boiled for 10 minutes before discarding.

Contact Management
Identification of contacts
Contacts can be defined as those persons who may have eaten suspected food. It is of great urgency to identify both the contacts and the suspected food as quickly as possible to prevent further cases.

Investigation and treatment
Close contacts who are known to have eaten suspect food should be kept under close medical observation for ≥3 days. If they can be contacted within six hours of exposure they should be purged to remove any unabsorbed toxin, using, for example, cathartics, gastric lavage and high enemas.