There are three forms of botulism -- foodbome (the classic form), wound and intestinal (infant and adult) botulism. The site of toxin production is different for each of the forms but all share the flaccid paralysis that results from botulinum neurotoxin. Intestinal botulism has been proposed as the new designation for what had been called infant botulism. This new name has not been officially accepted as of mid-1999, but will be generally used in this chapter instead of infant botulism.

Foodborne botulism is a severe intoxication resulting from ingestion of preformed toxin present in contaminated food The illness is characterized by acute bilateral cranial nerve impairment and descending weakness or paralysis. Visual difficulty (blurred or double vision), dysphagia (difficult in swallowing) and dry mouth are often the first complaints. These symptoms may extend to a symmetrical flaccid paralysis in a paradoxically alert person. Vomiting and constipation or diarrhea may be present initially. Fever is absent unless a complicating infection occurs. The case-fatality rate in the USA is 5%-10%. Recovery may take months.

In wound botulism the same clinical picture is seen after the causative organism contaminates a wound in which anaerobic conditions develop.

Intestinal (infant) botulism is the most common form of botulism in the USA; it results from ingestion of Clostridium botulinum spores with subsequent outgrowth and in-vivo toxin production in the large intestine. It affects infants under 1 year of age almost exclusively, but can affect adults who have altered GI anatomy and microflora. The illness typically begins with constipation, followed by lethargy, listlessness, poor feeding, ptosis (drooping of upper eyelids), difficulty swallowing, loss of head control, hypotonia (decreased tone of skeletal muscles) extending to generalized weakness (the "floppy baby") and, in some cases, respiratory insufficiency and arrest. Infant botulism has wide spectrum of clinical severity, ranging from mild illness with gradual onset to sudden infant death; some studies suggest that it may cause an estimated 5% of cases of sudden infant death syndrome (SIDS). The case-fatality rate of hospitalized cases in the USA is less than 1%; without access to hospitals with pediatric intensive care units, more would die.

Diagnosis of foodborne botulism is made by demonstration of botulinum toxin in serum, stool, gastric aspirate or incriminated food; or by culture of C. botulinum from gastric aspirate or stool in a clinical case. Identification of organisms in a suspected food is helpful but not diagnostic because botulinum spores are ubiquitous; the presence of toxin in a suspected contaminated food source is more significant. The diagnosis may be accepted in a person with the clinical syndrome who had consumed a food item incriminated in a laboratory confirmed case. Wound botulism is diagnosed by toxin in serum or by positive wound culture. Electromyography (a test of the electrical activity of muscles) with rapid repetitive stimulation can be useful in corroborating the clinical diagnosis for all forms of botulism.

The diagnosis of intestinal botulism is established by identification of C. botulinum organisms and/or toxin in patient's feces or in autopsy specimens. Toxin is rarely detected in the sera of patients.