European Foulbrood

European foulbrood (EFB) is a bacterial disease affecting honeybee larvae, caused by the Melisococcus plutonius bacteria. In spite of the name, it is not just found in Europe but is widespread--and can be found in North and South America, the Middle East and Asia.

Young honey bee larvae become infected with M. plutonius when they are fed contaminated food. The bacteria multiply rapidly in the mid-gut of the young larva, resulting in starvation just prior to capping. Some larvae may survive and enter the pre-pupal stage but die shortly thereafter.

Like American Foulbrood (AFB), EFB bacteria kill the larvae leaving empty cells left in the comb. However, EFB is much less serious than AFB. EFB shows up when the colonies have been under stress due to other diseases, colonies nearby, poor management and weather. EFB affects bee brood similar to AFB except that the disease affects open brood, i.e. the larvae are affected before they are capped. Approximately 10% of the larvae die after capping and this often leads to misdiagnosis because of the similarity to symptoms of American Foulbrood.

At the start of the main nectar flow, EFB mostly disappears or becomes non-detectable. The infestation may reappear in the fall. Re-queening seems to help because certain bee lines appear less susceptible than others (due to cleaning behaviour), and the replacement of the queen involves a break in the brood cycle of the colony.

Transmission

EFB is spread by mechanical contamination of honeycombs, and tends therefore to persist from year to year. It can also be spread by bees that survived infection as larvae, and spread the bacteria in their feces.

Symptoms

  • Larvae turn yellow, then brown, and die twisted against the side of the cell or melted at the bottom of the cell
  • Scales of larvae can be removed easily from the cell
  • Scale texture is rubbery
  • Most of the affected larvae die before their cells are capped
  • Brood has a "sour" odor
  • Caps sealing healthy brood are convex while those of diseased brood are concave and sometimes punctured

Cause

  • Melisococcus plutonius

Diagnosis

  • Clinical signs
  • Laboratory analysis

Treatment


  • Spray or sprinkle antibiotics (oxytetracycline) dissolved in 250 ml of sugar syrup over the colony every 3-4 days for 10 days. Note- Remove at least 6 weeks prior to main honey flow.
  • Remove all frames with significant numbers of affected cells.
  • Removing contaminated equipment with the "shook swarm" method along with the use of antibiotics

Prevention

  • Inspect brood frames regularly and be familiar with field symptoms.
  • Minimize robbing by preventing sugar spillage. Do not barrel feed.
  • Apply hygienic management practices. Clean hive tools, smoker and gloves after inspection of each apiary. Clean clothes regularly.
  • Replace brood frames after five years.
  • Requeening provides a distinct break in the brood cycle of the colony, allowing the bees to clean up existing disease. It may also provide new bees with better cleaning behaviour, i.e. less susceptible to disease.

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