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MCQs in Tropical Medicine

Rob Skelly DTM+H FRCP

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Answer 82 - Botulism

Typical features of botulism include:
False a. circumoral parasthaesia
False b. extensor plantars
False c. diarrhoea
False d. fever
True e. post-tetanic potentiation on EMG (electromyography)


Botulism usually results from ingestion of pre-formed botulinum toxin in canned or smoked food. The toxin is produced by Clostridium botulinum. It is heat labile. It acts pre-synaptically at neuromuscular junctions preventing the release of acetylcholine.

Features include ptosis, dry mouth, diplopia, blurred vision, bulbar palsy and muscular weakness. Sensory signs are not a feature. (Circumoral parasthesia is typical of hyperventilation.) Nausea and vomiting may occur but not usually diarrhoea. Symptoms occur 12-72 hours after ingestion of the toxin.

Diagnosis is by animal tests: mice are injected with small samples of serum, urine or gastric contents from the patient and watched for signs of botulism. EMG shows post tetanic potentiation.

Treatment. Respiratory support and polyvalent horse antiserum.

Copyright: Rob Skelly 2006