10.2019
Author Dr. J. Hower, paediatrician from Germany

Parents might feel that they are doing their children some good by feeding them honey every now and again. There is a risk, although rare, that if honey contains Clostridium botulinum, it could lead to infant botulism during infancy (not in childhood or adulthood). Affected infants will show signs of paralysis of the swallowing muscles and eye muscles, and need immediate medical attention.

Comment:
The Clostridium botulinum (Cb) toxin enters the bloodstream through the intestine and leads to a flaccid paralysis of the muscles and to neuromuscular transmission disorders in autonomic nerves due to the irreversible blockage of the cholinergic synapses. The different types of this toxin are classified from A to G, but only types A, B, E and F can cause human botulism.

Different forms of botulism
• Foodborne botulism occurs when pre-formed toxins are ingested with food.
• Wound botulism occurs when C. botulinum spores colonise an open wound.
• Infant botulism (IB) occurs when infants ingest C. botulinum spores, which germinate into bacteria that colonise the gut and release their highly potent toxin.

Infant botulism is a special form of botulism, as the responsible C. botulinum spores may enter the system from a variety of sources. These include soil, cistern water, dust and food. Honey is therefore only one potential source. Even though honey has antiseptic properties, it may still contain spores that end up in the infant’s intestine.

Prevalence
In Europe, there have only been a few isolated cases since 1993. A striking feature of IB is the age distribution: About 95% of cases occurred in infants between the age of 3 weeks and 6 months. This means that its temporal pattern resembles that of sudden infant death syndrome. It is assumed that there is a connection, but this has not yet been conclusively proven.
As C. botulinum spores can be found almost everywhere in our surroundings, they are likely to frequently enter children’s systems without ever causing any clinical symptoms. The infantile intestine, however, seems to be a lot more susceptible to the germination of toxin-producing spores ingested with food. It seems that the majority of spores are ingested with dust particles, on which the spores travel. Even though it is only responsible for less than 5% of IB cases, parents can eliminate one root cause: Honey should not be fed to infants under the age of one year!
Honey is safe for older children and adults, who, as far as we know, will not fall ill from ingesting C. botulinum spores on food.

Scientists from California found C. botulinum spores in approx. 10% of samples of commercially available honey. Since many infants are exposed to the C. botulinum spores without falling ill, individual risk factors (diet, microbiome) seem to influence the risk of developing botulism. The minimum infective dose is not known. Based on the honey samples tested, it is assumed that 10 to 100 spores might be enough for an infection.

Symptoms
The infection is not always clinically diagnosed. The first sign of IB is generally constipation, followed by difficulties with drinking, lethargy, and respiratory paralysis. Mild cases of IB may often be overlooked. The mortality rate is 2%. The symptoms often persist for a very long time. However, most infants recover completely.

References:

Robert Koch Institute. Epidemiologisches Bulletin. Mai 2018; Nr. 20: 189- 198. URL (German): https://www.rki.de/DE/Content/Infekt/EpidBull/Archiv/2018/Ausgaben/20_18.pdf?__blob=publicationFile
U.S. Food & Drug Administration (FDA). Bad Bug Book: Foodborne Pathogenic Microorganisms and Natural Toxins Handbook Clostridium botulinum. URL: https://www.fda.gov/food/foodborne-pathogens/bad-bug-book-second-edition