Caused by Panaibacillus larvae
Which is a spore forming bacterium.
It exists only in spore and vegetative states. Only the spore state is contagious to bees.
AFB is a disease which affects the larva after it has been capped. A(fter)FB. When the infected larva dies the cell cappings change.
American foul brood
Bee larvae are infected by ingesting Paenibacillus larvae spores. These are fed to the by adult nurse bees in brood food.
Spores take a day to germinate inside the larval mid gut.
They form the vegetative form (rod stage) becoming bacteria
The rods penetrate the gut wall into other tissues where they proliferate rapidly. They continue to do so consuming the tissue until the larvae dies.
The white larvae then turns brown amd decays. This smells and the glue-like mass of larvae can be formed into a rope when pulled with a match stick.
Wax cappings become sunken perforated as bees try to undo them to remove the dead larva.
The cappings can become greasy looking and slightly darker than other cells.
It dries into a scale – dark brown – adhering to the side wall of the cell. These scales contain millions of infective spores which are removed by the bees as they attempt to clean up the cell. Once ingested they can be fed to brood as the job changes from cleaner to nurse bee.
These scales can be seen if you hold the frame facing the light as their rough surfaces can reflect the light making them noticable.
AFB is a notifiable disease. Which means the bee inspector must be contacted and the apiary put in standstill voluntarily until it is confirmed when it will be compulsory.
Brood inspections twice a year can identify brood diseases.
The spores can not germinate in the adult bee because of 10-hydroxydecanoic acid (10-HDA) which is produced in the worker bees mandibles.
The bacteria produces spores when the larva voids its guts prior to metamorphosis. This means the cell is then contaminated. The bacteria continue to multiply in the haemolymph until the death of the larva when again it will form spores.
Cleaner bees can carry spores around the hive into the honey and all frames.
Can be slow at first until the number of young bees declines and the disease takes control and kills the colony.
Once the disease is confirmed the bees and killed and burnt on the frames.
Compulsory destruction of infected colonies is a very effective measure.
Using a lateral flow test – take a sample of suspected infected larva and put it in the buffer bottle, shake for about 20 seconds and put 2-3 drops on the LFD. Two blue lines indicates positive.
Ways foul brood is spread
drifting, robbing, swarming
by bee keepers
buying infected bees
buying infected equipment
dirty tools and protective clothing between hives and apiaries
moving bees to areas with large numbers of bees
feeding honey from dubious source to own bees
feeding pollen collected from infected colony to healthy colony
moving combs about
uniting weak colony with disease with healthy.
not being brood health aware
housing unknown swarms in own apiary