Honey bee age-dependent resistance against American foulbrood

Abstract

American foulbrood is a fatal disease of honeybee larvae. Larvae become infected by swallowing spores of P. larvae larvae that contaminate their food. Adult bees who transfer the spores and have close contact with larvae never become infected. Resistance to this bacterium was investigated in various larval stages and in adults of different ages. Substances inhibiting the growth of P. larvae larvae could be demonstrated in 4 day old larvae and, to a lesser extent, in 1 day old larvae. No such substances could be shown in 6 day old larvae. Extracts of midguts of adult bees generally showed a stronger ability to inhibit growth of the bacteria than did extracts of larvae. It was discovered that the midguts of 8 day old adult bees show a higher growth-inhibiting potential against P. larvae larvae than midguts of freshly emerged adult bees or foragers.