Botulism usually results from eating improperly preserved foods, such as home-canned fruits and vegetables, sausages, and smoked or preserved fish or meat. Rarely, it results from wound infection with C. botulinum.

Botulism can result in respiratory failure and paralytic ileus.

The patient may report having eaten home-canned food 12 to 36 hours before the onset of symptoms.

The patient may complain of vertigo, dry mouth, sore throat, weakness, nausea, vomiting, constipation, and diarrhea. Concurrently or up to 3 days later, he may report diplopia, blurred vision, dysarthria, and dysphagia from cranial nerve impairment. Later, he may experience dyspnea from muscle weakness or paralysis. His body temperature will remain normal.

The patient may appear alert and oriented on inspection. Ocular signs may include ptosis and dilated, nonreactive pupils. Oral mucous membranes commonly appear dry, red, and crusted.

Palpation may reveal abdominal distention with absent bowel sounds.

Further assessment may disclose descending weakness or paralysis of muscles in the extremities or trunk—the major physical finding in botulism. The patient’s deep tendon reflexes may be intact, diminished, or absent. He won’t have pathologic reflexes or sensory impairment.

Identification of the exotoxin in the patient’s serum, stool, or gastric contents or in the suspected food confirms the diagnosis. An electromyogram showing diminished muscle action potential after a single supramaximal nerve stimulus also is diagnostic.