American Foul Brood (AFB)
American Foul Brood is a highly destructive bee brood disease caused by the bacterium Paenibacillus larvae. Spores germinate in the mid gut of young larvae through contaminated food. Larvae younger than 24 hours are more susceptible to infection. Once the brood cell is capped, the infected larvae usually die in a short period of time. The vegetative bacterium will also perish; however it will first produce millions of spores that spread throughout the hive, continuing the cycle. One of the most devastating aspects of AFB is its resilience, as it can remain viable for up to 80 years in honey and on beekeeping equipment.
The first visible signs of AFB are usually spotty brood patterns and holes in the capped cells that appear jagged or off-center. Capped cells can also appear sunken or ‘deflated’. American Foul Brood will emit a strong, unpleasant odour. Larval Scale, where the decomposed lavae appear as a dried ‘scale’ on the cell wall, along with Pupal Tongue, are distinct signs of AFB.
Hives and equipment infected with AFB must be destroyed by law in the EU and in most states of the U.S.A.
Diagnosing American Foul Brood
European Foul Brood (EFB)
Though considered less serious than American Foul Brood, EFB is a brood disease caused by the bacteria Melissococcus plutonius. Larvae consume the pathogen via food, which then enters the digestive system and takes nutrients from the developing larvae. Larvae then die before the cell is capped. There is also evidence linking the transmission of EFB to the bite of the Varroa Destructor mite (Kanbar and Engels 2003). As Melissococcus plutonius is not a spore forming bacteria, it is spread throughout colonies by robber bees and by contaminated honey and equipment. European Foul Brood is found in all continents that keep European honey bees and has been of particular concern in Switzerland, continental Europe, the UK and the U.S.A. Though colonies usually recover, it has been linked to colony collapse in severe cases.
European Foul Brood is most common in spring when brood rearing is at its strongest. The first sign of EFB can be a patchy and uneven brood pattern. Infected larvae will turn a yellow brownish colour and appear twisted or contorted. Like AFB, the decomposing larvae emit a strong, sour odour. Year on year EFB can occur due to the presence of Melissococcus plutonius spores on contaminated honey, foundations and equipment.
Mild EFB can be treated with OTC antibiotics, or the shook swarm technique. Requeening can also assist in cleaning out the colony. However if EFB is beyond treatment, colonies and equipment should be destroyed.
Chalkbrood is an infectious disease of the brood caused by the Ascosphaera apis fungus. The disease infects the gut of larvae and causes them to dry out and harden, turning white or grey in colour. The fungus is usually introduced to the hive by forager or robber bees.
The earliest sign of Chalkbrood is a white, cotton like substance covering the brood. As the infestation worsens, the substance will darken. The ‘mummified’ corpses of infected larvae can often be found at the hive entrance, placed their by worker bees demonstrating cleaning behaviour.
Increasing ventilation throughout the hive will help to stop the spread of the Ascosphaera apis fungus. Replacement of combs and frames can help with more severe cases, as can requeening.