B453 - EUROPEAN FOULBROOD

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B453 - EUROPEAN FOULBROOD

Nature of the disease
European foulbrood (EFB) is a bacterial disease of honey bee larvae caused by Melissococcus pluton.
Classification
OIE List B disease
Susceptible species
The honey bee Apis mellifera is susceptible.
Distribution
EFB has been recognised for a long time in Europe and North America. It has also been found in Africa, South America, India, Japan and Australia.
Clinical signs 
Most infected colonies display few visible signs that they are infected, which then often quickly abate spontaneously.
The sudden death of many larvae is common. Bee larvae usually die within 1-2 days prior to being sealed, or soon after.

In Australia mortalities of up to 90% have been seen in some colonies.

Severely affected brood may have a stale or sour smell.

Post-mortem findings 
Infected larvae that escape removal by adult bees and die first become flaccid and turn a light yellow colour, becoming increasingly brown and turn into a semi-liquid mass that dries out and forms a brown scale.
Differential diagnosis 
 
Specimens required for diagnosis 
Diseased larvae or those that have recently died should be collected for dissection and preparing smears. A sample of honeycomb, at least 10 cm x 15 cm with suspicious brood should be submitted for laboratory examination.
In the early stages of infection, bacteria can be cultured from dilute aqueous suspensions of diseased larvae.
Transmission   
Infection remains endemic within individual colonies because of mechanical contamination of the honeycombs by the organism, which is quite durable.
Infection is spread through infected foodstuffs when feeding larvae. It is transferred to neighbouring colonies by fled swarms of bees, by infected honeycombs, beekeeper accessories and non-disinfected beehives.
Risk of introduction   
EFB may be introduced with contaminated honey or beekeeping equipment.
Control / vaccines  
Infected colonies can be treated with antibiotics such as streptomycin and oxytetracycline. 

NB antibiotics can contaminate honey, so they must be used in accordance with directions.

Re-queening with resistant stock is used to "clean up" the disease in endemic areas. Hives and appliances should be sterilised by scorching with a blow torch.

To prevent spread, super and brood combs should not be exchanged between colonies unless it is known that all colonies are free. Colonies of bees should only be bought from disease-free apiaries.

References
  • Office International des Epizooties, 2002
  • ROOT AI (1990), European Foulbrood In ABC and XYZ of Bee Culture, ed Root Company, p 127-129