Black Queen Cell Virus (BQCV)
Krankheiten
The Black Queen Cell Virus, BQCV for short, mainly affects queen pupae.
The Black Queen Cell Virus, BQCV for short, mainly affects queen pupae. Affected queen pupae first turn yellowish, then dark to black, and die. The wall of the queen cell, which turns dark, gives the virus its name. Worker brood can also become infected, though the infection usually proceeds without noticeable symptoms there.
For beekeeping, the virus is particularly relevant in queen rearing and nucleus formation. If an above-average number of queen cells in a rearing batch fail to hatch and the cells are dark on the inside, BQCV is among the possible causes. Losses typically occur in spring and early summer, precisely the time when queens are being reared.
The connection with Nosema disease is very pronounced. Outbreaks frequently occur together with a Nosema infection, and mortality is considerably higher with a combined infection than with a single one. Studies show the highest loss rates when Nosema ceranae and BQCV occur together. Anyone wanting to avoid BQCV must therefore first bring Nosema disease under control.
There is no medication against the virus. In practice, comb hygiene, good pollen and food supply, avoiding stress in rearing, choosing healthy nurse colonies, and consistently low Varroa infestation all help. Breeding material should not be taken from conspicuous colonies, and nurse colonies should be free of Nosema symptoms.
Reliable detection is done in the laboratory using RT-PCR; BQCV is regularly recorded as part of monitoring projects. There is no reporting requirement. Suspect queen cells should not simply be reused, nor should nurse colonies with recognizable signs of disease be used for rearing.