Infant botulism (IB), also called "floppy baby" syndrome, is a neuroparalytic illness caused by a toxin of Clostridium botulinum. Clostridium botulinum is a gram-positive rod-shaped anaerobic bacterium that produces flaccid muscular paralysis by means of several toxins. It produces 7 known neurotoxins; types A and B are most commonly related to IB. Illness can be gradual or abrupt in onset, with constipation usually being the first symptom. It can then progress to descending symmetrical paralysis. It is the most common form of infectious botulism in the United States; the US Centers for Disease Control and Prevention (CDC) reports an annual incidence of 110 cases. The mean age of patients is about 13 weeks, although IB has been documented in patients as young as only a few days old.
Infection occurs from ingestion of C. botulinum spores. The minimal infective dose may be as low as 10-100 spores, which colonize in the gastrointestinal tract and produce a toxin that is then absorbed in the intestines. The botulinum toxin is the most potent bacterial toxin; its required minimal dose is a million times less than that of sodium cyanide. The toxin is transported by the bloodstream to the nervous tissue, where it irreversibly binds to the presynaptic cholinergic receptors. Once the toxin is internalized, it acts as a protease in the cytoplasm and blocks the release of acetylcholine. The lack of available acetylcholine at the neuromuscular junction for muscle excitation causes the vast array of symptoms of IB. Respiratory failure is the most severe complication, with about 50% of infants requiring mechanical ventilation.
Raw honey consumption is the classic associating factor in the literature (up to 25% of honey products have been found to contain spores of C. botulinum); however, most cases have no known honey exposure. Other risk factors are home-canned foods, ingestion of environmental dust, and living close to the sites of construction or cultivation. Infants seem more prone to develop IB at weaning. Formula-fed infants are typically younger at the onset of IB, with a more severe and rapidly progressive course. Meckel's diverticulum is a known risk factor as well.
Classical signs and symptoms include:
- Cranial nerve palsies (ptosis, sluggish pupillary reflexes, difficulty in suckling and swallowing, and diminished gag reflex)
- Poor feeding and constipation
- Weakness, lethargy, and hypotonia
- Weak cry
- Pooled oral secretions
- Signs of autonomic dysfunction (no tearing or salivation, blood pressure instability, and hot skin)
Symptoms are typically most severe 1-2 weeks after they initially begin. Recovery is slow but usually complete. Case fatality rate is <2%. Diaphragmatic function recovers before peripheral muscles, allowing the patients to come off mechanical ventilation early in the recovery period.
IB may be underestimated due to:
- Insufficient physician awareness
- Inaccessibility to appropriate laboratory tests
- Mild infections that do not require medical attention
- An association between the fulminant type of IB and sudden infant death syndrome (SIDS) has been noted; one study found C. botulinum toxin in 10 of 211 (4.9%) SIDS cases.
- Honey has been associated with IB in a number of case reports.