AFB is caused by a spore forming bacterium called Paenibacillus larvae. These spores are the infective stage of the disease and infection begins when food contaminated with spores are fed to larvae by the nurse bees. Once in the gut of the larva the spores germinate, bateria move into the larval tissues, where they multiply enormously. Infected larvae normally die after the cell is sealed and millions of infective spores form in their remains. Spores are very resistant to extremes of heat and cold, and to many disinfectants and remain viable for many years.