Case Definitions

Suspected case

Clinicians should be alert to the possibility of cases of botulism. Any previously healthy patient with afebrile, descending, flaccid paralysis with an onset of hours to 8 days should be immediately reported to the Consultant in Communicable Disease Control at the local Health Protection Unit.

In the event of a suspected deliberate release of botulism, a higher index of clinical suspicion should be maintained and the diagnosis considered if the symptoms outlined below present at medical services, especially if they arise in persons who have been within or in close proximity to the exposed zone. The level of suspicion of botulism depends on clinical symptoms and the circumstances, but if a case is suspected, microbiological specimens should be sent to the reference laboratory to eliminate or confirm the diagnosis, and empirical treatment should be considered in the interim.

The symptoms of botulism are due to muscle paralysis caused by the toxin.

Symptoms in adults include:

• Blurred or double vision, drooping eyelids, enlarged or sluggishly reactive pupils, slurred speech, difficulty swallowing and dry mouth, loss of head control, generalised hypotonia and weakness. Loss of the protective gag reflex may necessitate intubation and mechanical ventilation.
• Deep tendon reflexes may be present initially but diminish or disappear in the ensuing days.
• Diarrhoea, nausea and vomiting, followed by constipation, may occur in food-borne botulism.

Infants with intestinal colonisation botulism appear lethargic, feed poorly, are constipated, and have a weak cry and poor muscle tone as well as symptoms in adults described above.

In untreated persons, death results from airway obstruction (pharyngeal and upper airway muscle paralysis) and inadequate tidal volume (diaphragmatic and accessory respiratory muscle paralysis).

Clinical tests that may help distinguish between other differential diagnoses include brain scan, CSF examination, nerve conduction tests (EMG), and a Tensilon test for myasthenia gravis.

Confirmed case

A case that clinically fits the criteria for suspected botulism, and in addition the results of one or more pathological specimens fit one or more of the laboratory criteria for diagnosis.

Laboratory criteria for diagnosis

Detection of botulinum toxin from serum or other body fluids and/or isolation of C. botulinum from a patient with a compatible illness is diagnostic.

Last reviewed: 31 March 2009