Adult house bee intervention
The disappearance of disease symptoms in a colony is due to the hygienic behaviour of honey bees.
Adult house bees can be very efficient in recognising and removing diseased brood. For instance, in one trial 50% of the diseased larvae were removed before they were 11 days old, which is before such larvae show any visible symptoms of the disease and before spores are produced.
As well, a colony may produce diseased larvae and pupae containing spores, but the house bees can be so efficient at cleaning the cells that most of the new larvae reared in those cells will not become diseased.
Hygienic behaviour in honey bees is controlled at least partly by two recessive genes, one for the uncapping of cells, and the other for the removal of brood remains. The degree of hygienic behaviour varies between colonies, both because of the genetic composition of the worker bees, and because of the strength and age distribution of the colony population.
The more hygienic a honey bee colony is, the more resistant it will be to AFB infections.
It is possible to select for hygienic behaviour? See selecting breeding stock for hygienic behaviour.