How does American foulbrood spread between honeybee colonies?

American foulbrood is a highly contagious and serious disease affecting honeybee colonies, caused by the spore-forming bacterium Paenibacillus larvae (formerly Bacillus larvae).12

The disease spreads between healthy colonies primarily through two human-influenced activities:

• Transferring Equipment: Moving contaminated beekeeping equipment between hives can introduce the resilient bacterial spores to healthy colonies.1
• Feeding Infected Honey: Allowing bees to consume honey sourced from an infected colony provides a direct pathway for the transmission of the pathogen.1

Because these spores are exceptionally resistant to heat and chemicals, the disease is difficult to eradicate once established. Consequently, many jurisdictions and U.S. states mandate the destruction of infected colonies by fire to prevent further spread, and apiary inspectors are often employed to enforce these biosecurity regulations.1