Botulinum Toxin : Infant Botulism

by Food and Drug Administration (FDA)

(Page 2 of 3)

Infant botulism differs from food-borne botulism in that the toxin itself is not ingested. Instead, C. botulinum spores swallowed by the infant germinate and produce the toxin in the favorable environment of the baby's large intestine.

Because the spores are nearly everywhere in the environment, children and adults regularly ingest them, yet very rarely suffer ill effects. In a few cases, adults who have had intestinal surgery or whose intestinal tracts have otherwise been altered have contracted the disease the way infants do. This has led researchers to conclude that infants' as-yet "incompletely-developed intestinal flora," may be to blame, says Arnon, one of the co-discoverers of infant botulism in 1976.

Infant botulism is serious, but rare and not usually fatal. From 1976 through the end of 1993, 1,206 infant botulism cases were confirmed in the United States. About 75 to 100 cases are reported annually, about half of them in California (presumed to be due to the prevalence of C. botulinum spores in the state, its high number of births, and the pediatric community's familiarity with the disease, which results in more correct botulism diagnoses). All of the infant cases involve babies less than 1 year old; the disease is most common in the second month of life.

Infants' immature intestinal tracts offer a "window of vulnerability, and if a baby has the bad luck to swallow a botulism spore during that period, the spore has an opportunity to germinate," Arnon says. The spores travel with microscopic dust particles, so the researchers have concluded that most affected infants have simply inhaled the spores. "They mix with saliva, they're swallowed, and that's how they reach the intestine," Arnon says. Unfortunately, there is no way to prevent the disease in such cases.

But parents and other caregivers can prevent babies acquiring infant botulism from one source — honey. California researchers have isolated C. botulinum spores from about 10 percent of store-bought honey samples, and although less than 5 percent of infant botulism patients contract the disease from honey, health officials and pediatricians agree that honey should not be fed to infants under 1 year of age (it is perfectly safe for older children and adults).

The first sign that an infant has botulism is usually constipation, although this isn't always apparent to parents. Often the baby isn't brought to a doctor until parents notice other symptoms, such as lethargy and poor feeding as the paralysis begins to affect the baby's gag reflex and swallowing ability.

Because breathing is affected in the most severe stage of botulism-induced paralysis, researchers suspect a link between infant botulism and sudden infant death syndrome (SIDS), also known as crib death. One study done 15 years ago showed that about 5 percent of children in California whose deaths were attributed to SIDS actually had died from infant botulism. Because of the difficulty of conducting such studies, the link between SIDS and infant botulism remains poorly understood.

The infant botulism fatality rate is less than 2 percent, and recovery is usually complete. Often, however, infants have to spend weeks or months on a ventilator. Horse-derived antitoxin is not given to infants because of the risk of side effects such as anaphylaxis and serum sickness. But in February 1992, the California Department of Health Services began a new clinical trial that may provide a way of lessening the effects of the disease.

With funds from the FDA's Orphan Products Grants Program, the trial is evaluating a human-derived antitoxin obtained from laboratory workers who for occupational safety reasons have been immunized with botulinum toxoid, which is toxin whose poisoning potential has been removed.

The California investigators will assess whether infants given the antitoxin will have shorter hospital stays, fewer complications, and a halt to the progression of disease. Infant botulism represents the only opportunity to evaluate the safety and efficacy of human-derived botulism antitoxin (known formally as Botulism Immune Globulin) because of the sporadic and even less frequent occurrence of food-borne and wound botulism.

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.