In this form of botulism, the severity ranges from mild illness with failure to thrive to severe paralysis with respiratory failure. The first sign of the disease may be constipation. Other features include lethargy, hypotonia with poor head control, poor feeding, with difficulty in sucking and swallowing, and pooled oral secretions. Respiratory failure occurs in up to one half of diagnosed infants. The identification of contaminated honey as a source of spores has lead to the recommendation that honey should not be given to infants younger than 1 year.
Susceptibility decreases with age as the normal intestinal flora develops.
The major systemic features of botulism involve motor weakness or paralysis. Paralysis begins with cranial nerve involvement and progresses caudally to involve extremities. A generally symmetric descending paralysis occurs, with involvement of neck, arms, thorax, and legs. Respiratory difficulties occur with intercostal and diaphragmatic weakness. Autonomic features are to be expected, reflecting cholinergic neurotransmission disruption, with impairment of salivary secretion, paralytic ileus, constipation, and urinary retention.