Black queen cell virus (BQCV) is a disease that kills queen bee larvae or prepupae. Caused by the virus Cripavirus genus, it turns the developing bee yellow and eventually brownish-black.
Scientists believe Nosema apis, an adult honey bee disease, may transmit the infection. Beekeepers often see BQCV in spring and early summer.
Symptoms of black queen cell virus
As the BQCV develops, the queen bee pupae turn from pearly white to a yellowish shade, then black. The cell walls also turn dark brown or black. Source.
Beekeepers will also see a tough sac-like skin surrounding the larva. It looks the same as the layer resulting from sacbrood, often filled with liquid.
Adult bees only become infected with QBCV when carrying the microsporidian Nosema apis. Although these bees won’t display any signs of disease, their lives will be significantly shortened.
How does black queen cell virus spread?
BQCV is transferred among hives by foraging worker bees that pick up the virus on their travels. It remains viable on pollen, larval remains, honey, and in water sources.
Adult bees spread the disease during robbing, drifting, and swarming. Beekeeping activities can also move the virus between hives in the bee yard.
Food sources in the healthy hive become contaminated, then nurse bees feed it to their brood. The BQCV can remain active for up to four weeks.
Black queen cell virus is closely linked to Nosema apis. Researchers believe that Nosema may also help spread BQCV.
Related reading: What are some of the biggest bee threats?
Beekeepers can help keep BQCV in check with young fertile queens, proper nutrition, good hive location, and comb rotation practices. Using hygienic bee breeds and minimizing other diseases and pests are also helpful preventative measures.
- Using fertile queens: Regularly replacing old or underperforming queens helps the hive numbers grow fast, reducing disease susceptibility.
- Proper nutrition: Feed bees during scarce forage, like nectar dearths. It provides them with the energy to continue regular hive activities like housekeeping.
- Good hive location: Place hives in sunlit areas to deter harmful pathogens. Maintain proper ventilation to control humidity, especially in the cooler months.
- Comb rotation practices: Replace old, dark combs every 3-4 years to avoid pathogen buildup. Establishing a rotating comb system allows beekeepers to monitor the comb for issues.
- Hygienic bee strains: Choose bee strains known for hygienic behavior, which detect and remove infected brood efficiently.
- Minimizing other pests and diseases: Regularly inspect for threats like Varroa mites and Nosema. Use integrated pest management to reduce chemical reliance and keep apiary tools clean. Find out how to test for varroa mites here.
Beekeepers that breed queens for sale should take extra care around the black queen cell virus. Once detected, they should immediately cease distribution and contact their nearest lab to confirm its presence.
Beekeepers suspecting black queen cell virus should isolate the remaining hive brood and wait to see if the larvae become symptomatic.
There are no commonly accepted chemical treatments to eradicate the virus. Instead, all beekeeping equipment and tools should immediately be sanitized. Replace water sources where possible to help stop the spread.
How does BQCV replicate?
Below is a quick scientific explanation of how BQCV replicates. It includes a lot of biological terms, so if you skip this section, we’ll understand!
1. Entry into Cell
The virus penetrates the host cell using clathrin-mediated endocytosis, where cells engulf substances by forming vesicles from the cell membrane. This process begins once the virus attaches to a receptor on the cell. The virus’s coating is removed inside the cell, releasing its RNA genome into the cytoplasm.
Once inside, the virus replicates its genome. In dicistroviruses, the 5′ VPg protein enhances the translation of viral mRNA by inhibiting the host’s mRNA translation. ORF1 codes for replication enzymes, notably RNA-dependent RNA polymerase, aiding in RNA replication. The virus’s positive RNA strand is a blueprint for creating a negative RNA strand. This negative strand then generates more genomic RNA.
3. Viral interaction with the host
Black queen cell virus primarily infects the Apis honey bee genus. Infected insects can produce offspring, but they don’t survive.
Another critical interaction is the virus’s resilience against host defenses, thanks to a protective cap structure at the genome’s 5′ end. This cap guards the mRNA, ensures effective translation, and aids its journey to the nucleus for replication. Source.
Are there any associated diseases with BQCV?
Black queen cell virus is associated with several bee diseases, including sacbrood, and Nosemosis, heightening a bee’s vulnerability to BQCV.
BQCV is closely related to other viruses in the Dicistroviridae family, namely Israeli acute paralysis virus (IAPV), Kashmir bee virus (KBV), and acute bee paralysis virus (ABPV), all of which exhibit less pronounced symptoms.
Interestingly, the closest human counterparts to BQCV are hepatitis A and parechovirus.
Commonly asked questions
BQCV vs. sacbrood – what’s the difference?
Sacbrood and black queen cell viruses are easily mixed up. They both cause the larvae to darken with a plastic-looking, liquid-filled coating. Sacbrood multiples when ingested by young worker bees or larvae, while BQCV does not.
Does BQCV only use honey bees as its host?
While the honey bee genus Apis is the most common host for BQCV, it is also known to live off various bumblebee species.
Black queen cell virus detected in Canadian mosquitoes
Authors: Cole Baril, Christophe M R LeMoine, Bryan J Cassone
Our summary: Black queen cell virus (BQCV) commonly affects honeybee queen larvae. The transmission dynamics of this virus are not well-known.
This study used next-generation sequencing on Aedes vexans mosquitoes from Manitoba, Canada. They found BQCV, marking the first report of this virus in North American mosquitoes and mosquitoes in general.
The virus’s genome sequence showed a 95.5% similarity to a BQCV strain from Sweden. Results did not show evidence of the virus in other potential vectors. It also revealed no associated pathogens in the mosquito samples, but they did find plant sequences. These findings suggest mosquitoes might have acquired the virus from nectar sources shared with honeybees.