About the disease

American foulbrood (AFB) is a destructive bacterial disease of honey bees. This worldwide disease infects and kills honey bees in the larval stage. Bacterial spores are transferred to young larvae by nurse bees. The spores germinate in the gut of the larva as it transforms to the pupal stage, multiplying rapidly and causing death of the larva.

The dead larva hardens into a black scale on the bottom wall of the cell. A single scale can contain one billion spores; only 35 are needed to infect one larva. House bees cleaning out the cell distribute spores throughout the hive. Honey stored in these cells becomes contaminated. AFB spores from contaminated honey can spread the disease to young larvae.

Colonies weakened by AFB cannot adequately replace workers and are subject to robbing. Spore-contaminated nectar, honey, and pollen robbed from a diseased colony are spread to healthy colonies three to five miles away. Colonies inevitably die from foulbrood. The bacterial pathogen that causes this disease, Paenibacillus larvae, produces long-lasting spores that can remain viable for over 40 years. Spores are resistant to extreme temperatures, changes in weather, and antibiotics, making disease-management a challenging prospect.

Watch this webinar by Jim Tew, Alabama Cooperative Extension to learn more about AFB.

Symptoms of AFB

Management strategies

If AFB is detected

Treating AFB with antibiotics in Ohio: as of 1/2017