Which disease (B6) ?

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Correct answer: 3 (American foulbrood)

American foulbrood is a highly contagious bacterial disease of honey bee brood and is now present on all continents. It is caused by the pathogen Paenibacillus larvae. The disease does not arise spontaneously but is attributable to a source of infection that should, if possible, be identified to ensure effective control. According to the epizootic disease regulations, beekeepers are required to report not only confirmed cases of American foulbrood but also any suspected cases to the local apiary inspector (Art. 61).

A honey bee colony with good vitality can contain the disease for a certain period by removing affected larvae. Clinical symptoms appear only when diseased larvae remain in the combs due to the spread of the disease, insufficient brood care, and reduced cleaning behavior; this generally occurs only when the disease is already at an advanced stage.

Field symptoms and diagnosis:

• reduced number of bees (weakened colony)
• patchy brood areas
• some cells remain capped; bees do not emerge, particularly at the edge of the brood nest
• perforated cappings
• dark-colored, flattened, or slightly sunken cappings
• matchstick test: a light- to dark-brown rope forms beneath the capping
• tongue-shaped, flat, dark brown to black scales along the lower edge of the brood cell
• putrid odor

Such abnormal signs in the brood must be reported immediately to the apiary inspector. The inspector assesses the colonies and classifies them as healthy, suspect, or diseased. In cases of suspected disease or diagnostic uncertainty, brood samples showing signs of disease are taken and sent to an analytical laboratory. If the clinical symptoms of American foulbrood are unequivocal, the inspector may dispense with sampling and laboratory diagnosis.

What can the beekeeper do?

It is recommended to strengthen bees’ natural defenses against disease by applying the principles of good beekeeping practice. Colonies are healthy when they develop well (adult bees and brood), display good hygienic behavior, and produce good yields. In practice, these are referred to as strong or vital colonies (see cover image). Colony vitality depends on many factors. Beekeepers mainly have the following levers of influence:

• Apiary locations with good nectar flows (continuous food supply) and a suitable local climate.
• Regular creation of young colonies and replacement of weak colonies.
• Selection of queens with sufficient vitality traits (colony development, hygienic behavior).
• Regular renewal of combs.
• Varroa mite control in accordance with regulations – hygiene in the apiary.
• Caution when taking over bees from other locations (diseases!).
• Avoid any importation of bees from regions outside Europe.

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