Botulism is a disease caused by a toxin produced by the bacteria Clostridium botulinum. The condition is suspected based on a patient’s symptoms and the details they give regarding exposure to the bacteria. Botulism is often also suspected in cases of large outbreaks. Initially, botulism may go unnoticed in an outbreak and only get diagnosed retrospectively, once more people have been affected or when those first infected start to develop serious symptoms of the infection.

In adults, some of the clinical features of botulism include an acute onset of gastrointestinal symptoms along with a dry mouth and signs of central nervous system involvement such as blurred vision, slurred speech, difficulty swallowing, weakness and muscle paralysis. In infants, difficulty feeding and loss of muscle tone along with a reduced ability to suck are indicators of the disease.

In cases of food-borne botulism, recent consumption of canned or undercooked foods and infection among family members are often indicators. Wound botulism is usually characterized by the presence of an infected wound.

In adults, other conditions that present with similar symptoms to botulism may need to be ruled out and examples include myasthenia gravis, stroke, Guillain-Barré syndrome, poliomyelitis, diphtheria, bacterial or other food poisoning and tick paralysis. In cases of infant botulism, other conditions that may need to be ruled out include meningitis, electrolyte imbalance, metabolic encephalopathy, Reye syndrome, Werdnig-Hoffman disease, Leigh disease and congenital myopathy.

An outline of the steps taken in diagnosing botulism is given below:

• A detailed history of possible exposure is obtained and symptoms are assessed
• Samples of contaminated food may be examined
• Samples from wounds are sent for culture and toxicity testing in the laboratory
• Routine tests that may be performed include serum electrolytes, renal and liver function tests, urinanalysis, analysis of the cerebrospinal fluid (CSF) and electrocardiograms.
• Imaging studies such as a computed tomography (CT) scan or magnetic resonance imaging (MRI) scan are used to rule out stroke.
• Electromyography (EMG) can be used to detect muscle weakness and paralysis. This test can also help distinguish myasthenia gravis and Guillain-Barré syndrome from botulism.
• Blood or stool samples may be taken and sent for analysis.