American foul-brood (AFB) is a serious infectious of honeybee larvae and pupae. Infected bee colonies slowly become weak and die. Early detection of the disease is important because routine apiary management and interchange of hive components can easily spread it to healthy bee colonies.
Cause and Lifecycle
AFB is caused by the bacterium, Paenibacillus larvae. The spores of this organism cannot be seen by the naked eye.
The disease begins in honeybee larvae after they swallow AFB spores with their food.
Within 24-48 hours, the spores germinate in the gut of the larva and invade the body tissues, killing the infected larva before pupation, usually immediately after the brood cell is capped.
The final stage of the bacterium lifecycle is reached when it forms into spores. Approximately 2,500 million spores may occur in the remains of a single infected honeybee larva.
AFB spores are tough and can remain dormant for at least 50 years and possibly much longer. They can remain dormant on beeswax combs, used hives and components, honey, wax and propolis. They are very resistant to heat, direct sunlight, desiccation, fermentation, chemical disinfectants and veterinary drugs.
In healthy colonies, the brood pattern usually appears regular or uniform because the queen has methodically laid eggs across the comb, or in an area formed by a semi-circle or in concentric circles. Sometimes, there may only be a few empty cells interspersed in the area of brood. The caps of cells containing healthy brood are uniform in appearance, generally bright and convex.
If AFB is suspected it is important to obtain an accurate diagnosis. Experience has shown that diagnosis provided by a fellow beekeeper may not always be accurate. An inaccurate diagnosis can lead to spread of the disease throughout the apiary and large losses of hives and honey production.Confirmation of AFB may be obtained by laboratory examination.
Keep hives showing signs of disease isolated from hives that appear healthy. Make sure you do not transfer infection. Do not use infected material in healthy hives. Do not transfer combs or any hive components from diseased to healthy hives. Kill infected colonies as soon as practical and either prepare for irradiation or burn infected material in a hole and cover remains with at least 30 cm of soil. Take note of any fire restrictions.
Always handle healthy hives before diseased ones.
Do not feed antibiotics to infected hives as this only masks the problem.
Always inspect weaker non-performing colonies to determine the reason.
Do not expose honey to robber bees.
Do not under any circumstances allow infected colonies to die out and allow robber bees access to infected material. This will seriously increase the disease problem in the apiary and surrounding area.
Re-examine your hives every two months to make sure that you have found all the diseased hives.
These videos have been developed to advise on techniques that will assist in the identification and management of these two serious disease and pest threats.