Bees for Development Journal 122 March 2017
Bee diseases - a worldwide problem Bees are suffering increasingly from diseases. In addition to changing environmental conditions and application of pesticides, increasingly profit-focussed hive management systems contribute to this situation. The worldwide trade of bees and their products constantly confronts bees with the challenge of new diseases and parasites. Protection against diseases within the bee colony Honey bees are socially organised insects. Their colony consists of ten to fifty thousand infertile worker-bees, a number of males (drones) and one egg-laying female, the queen. However, a bee colony is far more than the sum of its individual bees. Like cells in higher organisms, they are able to cooperate via neuronal stimuli and hormones. The individual bee owns a cellular and humoral defence system, similar to higher animals, and their social defence system is of major importance. Old and ill bees die on forage flights or are rejected from entering the hive on their return. Furthermore, the hygienic behaviour of the bees involves the removal of ill brood from the nest. This hygienic behaviour is genetically fixed and more or less obvious within the different breeding lines, bee races and species. The negative effect of the pathogens and parasites is revealed by a shortened lifespan, a modified morphology, physiology or behaviour of the individual bee. For the colony, the consequences are a reduction of colony strength until it approaches collapse.
Photo © Wolfgang Ritter
Dr Wolfgang Ritter, Bees for the World, Germany
The yellow remains of larvae killed by EFB Diseases are spread within the honey bee colony, and between honey bee colonies. A horizontal transfer of diseases means the transfer of pathogens or parasites within the colony from bee to bee, and from colony to colony. A vertical transfer means that the pathogen is transferred ‘down through the generations’ from the queen, the drones or the workerbees to the brood. Between apiaries, diseases are spread by swarms and by beekeepers’ interventions.
Bee diseases have different causes Like other animals, honey bees can be infested by different pathogens or parasites. In addition to fungi and bacteria, viruses have become increasingly important, because they are transferred by parasites. Most of the parasites found with bees are mites and other insects.
Foulbrood is spread worldwide American foulbrood (AFB) and European foulbrood (EFB) have been spread nearly all over the world. However, AFB and EFB do not present a serious problem for 8
honey bee colonies everywhere, and often colonies are able to heal themselves. In Africa foulbrood has importance only where bees are kept in the industrialised American/European way, using frame hives. The conventional African way of beekeeping allows bees to swarm. (Formation of artificial swarms is commonly used to control foulbrood in Europe.) In many countries, for example in USA, antibiotics are used for control of foulbrood. However, their use masks the infectious disease with the effect that after the end of the treatment, a relapse happens. Moreover, this introduced the risk of residues in honey.
Nosemosis has different kinds of pathogens Nosemosis represents a diarrheal disease of the bee caused by a fungus. The pathogen destroys the bee’s midgut epithelium where it multiplies inside cells. As long as the infested bees are able to defecate outside the hive or die there, the bee colony is able to heal itself. With increasing infestation, the bees are more likely to defecate within the nest. When other bees pick up the faeces to
