Roe Valley Beekeepers Association
An account of the signs and symptoms of American Foul Brood and European Foul Brood and their development within the colony.
Both AFB and EFB are brood diseases affecting the colony brood and carried by workers, which are themselves unaffected.
American Foul Brood (AFB) is caused by a spore forming bacterium (Paenobacillus larvae) which is carried to the larvae by nurse bees whilst feeding. The spores are highly resistant and may exist for many years. The larvae absorb the bacteria through their gut, entering the haemolymph from the proventriculus, and causing a septicemia. The larva will succumb to this infection, and its remnants contained within a sealed brood cell, will degenerate and liuquify into a sticky globular mass. Within this large numbers of spores are formed. The colonies attempts to investigate the larval death, and to clean the call will result in further spread of the spores to other bee larvae. Death of developing larvae will deplete the colony which may thus perish. Within the diseased colony the spores are transmitted by bees as described, and infection may also be transmitted to other hives and apiaries by bees during robbing and drifting, and by beekeepers tools, and equipment and by the transfer of infected hive components purchased. The signs of disease are a weakened colony. The brood frame will exhibit a pepperpot appearance of affected and unaffected brood. Affected cells will have shrunken greasy looking cappings, and some of these will have been perforated (opened) by worker bees investigating the larval death. Looking into cells, one may see larval tongues protruding towards toe opened top, and dark scales adherent to the emptied side wall of the cells. These fluoresce under UV light. Cells containing dead larvae, if poked with a matchstick can produce a characteristic stringy goo. If secondary infection results there may be an offensive smell in the hive. Management of this notifiable disease is to immediately close the hive and to notify the Senior Bee Inspector. His advice must be followed and he will wish to inspect the hive, and subsequently other hives in the apiary and in neighbouring apiaries in the area in a 3 mile radius. He will also wish to follow all contacts particularly if the disease has been introduced by the purchase of second hand equipment or colonies.
Treatment of diseased colonies is by destruction by burning of all comb and frames, and sterilisation of other hive components by flame and immersion in bleach. There have been those who have attempted to kill this disease using antibiotics, a plan which is both futile and dangerous. Antibiotics will not kill spores which may exist for many years, and the failure to deal effectively with diseased colonies will ensdure spread to others.
European Foul Brood (EFB) is a disease of open brood caused by a bacterium (Melissococcus Pluton). This non-spore forming bacterium is introduced to the larvae by nurse bees when feeding, and can live within the adult bee gut. Ingestion by larvae results in an inflammatory reaction to the ventrculus wall which causes damage to the endothelial layer. This results in failure of protein absorbtion. Protein is particularly necessary for the larval development and its loss will affect the larva, and may result in its death. The larvae becomes distorted and twisted as if in pain with cramp, and will undergo a colour change from pearlescent through creamy white to greenish before perishing. The disease is spread when adult bees attempt to extract and clean the larval remnants, and in so doing reinfect their mouth parts and gut, thus ensuring tat the bacterium is passed on to other bee larvae. The disease is relatively uncommon in Ireland compared to AFB, but is also a notifiable disease. Its spread into a colony may be by drifting, robbing or via drones, or by the purchase of infected colonies or contaminated equipment. Following suspicion the Bee Inspector will inspect the colony to differentiate this disease from other brood diseases notable sac brood, and will investigate the outbreak, including its origin. This would require inspection of other hives and apiaries and of contacts. The treatment options which he will consider will include destruction of the colony if heavily infected, or the use of oxy-tetracycline antibiotics in feed if less so. This can not occur when a commercial honey crop is present and this would have be discarded to avoid antibiotic entry into the human foodchain. Another method used is to use a process of shook swarm in which the colony is repeatedly moved to fresh foundation and fed so that they leave behind infected brood and brood cells. The process will need to be repeated several times to ensure its effectiveness