Sacbrood
Krankheiten
Sacbrood is caused by the Sacbrood Virus, SBV for short, and is among the most widespread bee viruses.
Sacbrood is caused by the Sacbrood Virus, SBV for short, and is among the most widespread bee viruses. Symptoms appear only in the brood. Adult bees do not show visible illness but carry the virus in their brood food glands and pass it on to young larvae when feeding. Cleaning bees pick up the virus while cleaning cells and thus become part of the cycle within the colony.
The larva dies as a stretched larva before its first pupal molt. Because the outer skin remains intact and fluid collects underneath, the larva takes on the characteristic sac-like shape when pulled out of the cell. When it dries, a dark, boat-shaped scale remains, which can be lifted out of the cell easily. In the colony, a patchy brood nest, cells opened by the bees, and perforated or sunken cell cappings can be seen.
The most important task in the field is distinguishing it from foulbrood. In sacbrood, the mass does not form threads, and the scale does not adhere firmly to the cell wall. In any case of doubt, especially with stringy contents, a certified bee inspector or the veterinary office (Veterinäramt) should be consulted, since this raises suspicion of the notifiable American Foulbrood.
There is no medication. Beekeeping measures are effective: removing and melting down heavily affected brood combs, because the virus is heat-sensitive, providing the colony with plenty of food and pollen, ensuring a continuous nectar flow, lowering Varroa infestation, and requeening with a young queen from a line with good hygienic behavior. A strong colony often heals sacbrood by itself once conditions improve.
Moving affected brood combs into healthy colonies should be avoided. There is no reporting or notification requirement in Germany or Austria, but sacbrood is recorded as part of monitoring projects.