Sacbrood virus is an RNA virus of the picornavirus family. This virus only affects bee brood; infected adult animals do not show any symptoms. Transmission occurs through the bees that take up the virus when removing dead larvae and afterwards excrete it again through the hypopharyngeal glands when feeding. The virus can survive winter dormancy in the salivary glands.
Infected larvae die shortly before pupation and become small, fluid-filled “sacs” which later dry out and become scab. The brood pattern shows sunken caps. Sacbrood is considered a so-called secondary infection, since the disease usually only takes on a severe course if the colony has been weakened by a primary infection, such as varroosis. For the therapy of the swarm, affected combs can be removed and melted. Transmission occurs through the bees themselves or through the beekeeper.