Visual Indications of AFB
American Foul Brood (AFB)
Bacterium: Paenibacillus larvae
American foulbrood is caused by a spore forming bacterium Paenibacillus larvae. Young honey bee larvae become infected when they consume P. larvae spores in their food. The spores germinate in the gut; bacteria then move into the gut tissues, where they multiply enormously in number. Infected larvae normally die after their cells are sealed. Millions of infective spores are formed in their remains, which dry to form ‘scales’ that adhere closely to the cell wall and cannot easily be removed by bees. Consequently brood combs from infected colonies are inevitably severely contaminated with bacterial spores. If the scales go unnoticed and infected combs are subsequently used or moved from colony to colony during routine beekeeping management, then infection has the potential to spread quickly.
The spores are very resistant to disinfectant and to extremes of heat and cold. They retain their powers of germination for many years in honey, in old combs kept in store or in derelict hives, skeps or boxes.
Once a colony is infected the disease will usually progress until most of the brood is affected. The colony then becomes unable to replace the ageing adult bee population, causing it to become weakened and, finally, to die out. The disease may develop for months before the colony succumbs.
Death may occur at any time of the year. Affected colonies are killed and combs are destroyed by fire.