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The Black Queen Cell Virus (BQCV) is a viral disease of honey bees, found in all beekeeping regions of the world. It is particularly deadly to the Apis mellifera, Apis florea, and Apis dorsata (Giant bee) species of the honey bee.
The beekeeping industry is under many threats including loss of habitat, diseases and pests. Honey bees suffer from many diseases which affect their population and productivity. Some diseases can wipe out entire colonies if unchecked. Viral diseases are some of the most serious afflictions to bees in the world and need to be put in check.
The unchecked spread of diseases such as the Black Queen Cell Virus in honey bee colonies negatively affects the agricultural sector across the world, because of agriculture’s dependence on bees for pollination. It is therefore very important to understand the causes, course and control of diseases afflicting bees, to be in a position to protect the bee colonies that are so valuable to the whole agricultural industry.
What is the Black Queen Cell Virus?
A virus is an infectious agent that invades (parasitizes) a host cell to replicate. The Black Queen Cell Virus is caused by a Cripavirus. It is a devastating disease which primarily causes death of the queen bee pupae and larvae, with affected brood turning yellow to brown/black. The virus is thought to be one of the most common causes of honey bee queen larvae death in many areas throughout the world.
The Black Queen Cell Virus was first described in 1977 and its genome sequenced in 2000. The virus’ main host was identified as the honey bee genus Apis, although some bumblebee species also host this virus. It is most commonly found in Australia and now parts of South Africa. However, this virus has spread fast to other parts of the world and it is not uncommon to find elsewhere.
The Black Queen Cell Virus enters the host cell in a honey bee by endocytosis (a process where substances are brought into the cell). Honey bee cell buds inward to let vesicles from the virus into the cell. Some of the proteins that are endocytosed into the honey bee cell, are whole RNA or fragmented RNA. Once these vesicles burst in the cell of the honey bee, they allow release of the viral genome into the cell.
Transmission of the Black Queen Cell Virus
The disease gets into the larvae from nurse bees when they inadvertently feed the brood infected food. Again, adult bees can spread it by moving from hive to hive. Queen bees, if infected, will also spread it when they are introduced to other hives. Water and related beekeeping equipment may also carry the virus and cause transmission between hives.
The virus itself remains in dead larvae, pollen and honey for up to four weeks which can lead to continued spread. In apiaries concerned with queen bee production, there is more likelihood of finding this disease as it spreads through the introduction of infected queen bees. However, the disease can still be found even in small operations. Various studies put the Black Queen Cell Virus as second only to the Deformed Wing Virus, in terms of severity and spread.
Symptoms and Diagnosis of the Black Queen Cell Virus
The Black Queen Cell Virus has a major impact on a colony once it infects it. With a functioning queen and other adult bees, eggs are laid just like in normal times. However, the offspring that is raised to be a queen bee will not survive. This means that the colony is likely to suffer or feel pressured because it cannot raise a new queen bee.
As its name indicates, the Black Queen Cell Virus primarily attacks developing queens. However, the virus can still be found in worker and drone bees. Though, infected adults will typically not show any symptoms if infected.
The Black Queen Cell Virus kills its host larvae at different stages of development, so the remains of the dead larvae can be seen at any point after cell capping. The typical symptoms are fairly easy to observe but this requires an examination of the inside of the beehive to reach the combs.
When the virus attacks a colony, queen larvae and or pupae will turn yellow then darken from brown to black and die. The larvae usually develop a tough skin at first but will eventually be soft and dead. As the darkening of the queen larvae and pupae progresses, the exterior walls of the queen cells take on an oily look, taking a darker shade until they are black, an indication of dead pupae or larvae inside. It is important to note that only queen cells are affected.
Larvae and pupae death may also be caused by other diseases. As such, to ascertain the presence of the virus in a suspect colony, a proper diagnosis is required.
It is difficult to ascertain the presence of the virus by merely looking at the mentioned symptoms. Certainly, the problem is compounded by the fact that infected adult bees show no symptoms of infection. More importantly, though the virus visibly affects the pupae and larvae of queen bees, these (larvae and pupae) come from queen bees that seem healthy and show no symptoms of being infected with this virus. The virus only manifests itself with visible symptoms in the larvae and or pupae.
Once the disease is suspected in a colony, the surest way to ascertain its presence is to do a Polymerase Chain Reaction (PRC) test. Like other viruses, detection is typically detected by this procedure, a common molecular technique that brings out the unique genetic signature of a specific virus. Every virus has its unique signature and if it is matched during a PRC procedure, there can be no doubt about the presence of the particular virus. Unless the genetic signature of this virus is matched, then one cannot be sure of its presence despite the symptoms, as other viral infections can have the same symptoms.
Treatment for the Black Queen Cell Virus
Virus diseases are difficult to treat. Unfortunately, there is currently no vaccine or medication for the Black Queen Cell Virus. Once a colony is infected, no medication or vaccination will eradicate the virus. Simply put, there are no treatment forms available to treat honey bees infected with this virus. Once the virus has been confirmed in a beehive, the beekeepers must immediately sanitize all equipment that has been used on that hive. Additionally, standing water sources and containers should also be fully cleaned and sanitized as the virus can be spread through the water as well.
1. Cultural Control Methods
Cultural control methods are touted as the best option in controlling this viral infection. To reduce spreading the disease, hive hygiene maintenance and sanitation are seen as the best way. Hygiene maintenance includes regularly cleaning the hives and avoiding the use of possibly contaminated equipment. For this reason, beekeepers are advised to refrain from sharing equipment and clean their hives regularly. Also, the beekeeper should always sanitize their equipment with diluted ethanol or through heat (flaming).
Sanitation practices including replacing the comb of the hive and requeening are recommended. Highly infected colonies can be destroyed entirely to stem spread, should the colony abscond to start afresh elsewhere. This is an extreme measure that most beekeepers will wish to avoid though.
Ensuring that the colony is strong and well fed is another way that is touted to control the virus. It has been observed that poor and weak colonies are more susceptible to this disease than stronger ones.
2. Use of Antibiotics
Some studies have associated certain other infections with the Black Queen Cell Virus, in particular, the Nosema disease and Varroa mite’s infestations. The control of Varroa mite and treating Nosema are thought to aid in stemming invasions of this disease.
Some beekeepers allege that the antibiotics Fumagillin and Terramycin (Oxytetracycline HCL) can clear up symptoms of the Black Queen Cell Virus. These antibiotics act to disrupt potential interactions with Nosema disease. However, this has as yet to be ascertained. Using such antibiotics is thus not recommended. As of now, there is no scientific evidence to support the use of antibiotics in clearing the virus. After all, the FDA has not registered any antibiotic for use against the virus. The evidence is only anecdotal and inconclusive.
Using antibiotics in any attempt to eliminate this virus is not recommended. However, in the absence of any other viable strategy, beekeepers can use it as part of an integrated pest and disease control approach. The Black Queen Cell Virus interacts with parasites to make the virus more prone to causing mortality. Parasites, particularly the Varroa destructor, are commonly found in bee colonies that are also infected with viruses. The parasites can activate the virus if it is latent and can also act as a vector to transmit the virus to other uninfected bees.
Varroa Mite Control for Black Queen Cell Virus Management
Varroa mites are one of the honey bee parasites that are closely associated with the Black Queen Cell Virus. They transmit the virus between beehives and within individual beehives. Beekeepers have had great success in keeping the Black Queen Cell Virus under control by controlling Varroa mites in their apiaries. The success comes in preventing occurrence of the disease in honey bee colonies and in mitigating the effects of infections.
Beekeepers with any size of beekeeping operation can use Varroa mite control methods in their apiaries with ease.
Varroa Mite Control Methods
Both beginner and experienced beekeepers have the following major Varroa mite control methods at their disposal:
- Apistan is a packaging of chemical treatments. It comes in the form of strips that are placed around the beehive. The strips release the fluvalinate miticide in the beehive. Contact with bees is required for spread of the miticide throughout the hive. Placing the strips near the brood area is recommended. Careful with its use though, as Varroa mites can get resistant to miticides such as fluvalinate.
- Checkmite+ is an option available if your Varroa mites show resistance to fluvalinate. It is a strong miticide that has proved a little difficult to use safely for beginner beekeepers. Experienced beekeepers have no difficulties using the miticide in their beekeeping operations.
- Formic acid in various preparations and methods of delivery.
- Thymol in a gel matrix or other delivery methods, is a reliable natural treatment for control of Varroa mites. Commercially, it is available in the brand name Apiguard. Alternating between fluvalinate and thymol treatments, helps prevent the development of resistance by Varroa mites to any one of the two miticidal treatments.
Dusting for Black Queen Cell Virus Management
Powdered sugar dusting triggers bees to engage in grooming behavior. They brush Varroa mites from their bodies. This separation can be ensured by using an trap oil trap to make sure the Varroa mites do not climb back onto bees. You can also use a screened bottom board in the beehive to allow the mites to drop out.
Drone Comb Manipulation for Black Queen Cell Virus Control
Drone comb manipulation as part of hive and apiary management, can be used to suppress the development of Varroa mites in the beehive. By interrupting cycles in the brood of bees, you deny Varroa mites the perfect lifecycle. Periodic removal of deliberately placed drone brood frames from the beehive allows you to capture developing Varroa mites, because the adults prefer to lay eggs in the large drone brood cells. The removal of entire generations of Varroa mites from the beehive keeps the number of Varroa mites low and can even cause elimination of the problem from your beehive if done well. You can couple drone manipulation for Black Queen Cell Virus control with use of Apistan or Apiguard.
How to Choose Varroa Mite Control Methods
Choosing one or more of these methods to use in controlling Varroa mites and the Black Queen Cell Virus is up to the beekeeper. Using more than one method allows you to keep pressure on Varroa mites and prevent them from developing resistance to one control method. The final decision should be one that keeps you free of Varroa mites in your beehives and works within your comfortable expenditure range.
Some of the available methods to control Varroa mites and the Black Queen Cell Virus disease are invasive and cause a lot of stress to bees. You should also consider their persistence in the beehive. Disruptions when the treatments and control methods are applied are another factor you should weigh. Messes created when using some methods to control Varroa mites can turn costly. The potential to cause a fire in the beehive and the fact that you bring a fire close to the beehive should be at the fore of your mind, and adequately addressed, if you use methods such as vaporization and fogging.
Viral Replication of Black Queen Cell Viruses
Viral genome replication of the Black Queen Cell Virus is occurs once it has entered a honey bee cell. Among the proteins that are endocytosed into the honey bee cells under attack, is one called the VPG protein. It primes the cell for production of RNA. However, the protein blocks production of cellular RNA in the genetic code of the honey bee. The cell embarks on production of the RNA of the virus. RNA and DNA are closely linked, however viruses often require RNA only for their existence.
Honey bee cells infected by the Black Queen Cell Virus try to fight back against it. They do this at the cellular level and attempt to counter the production of virus parts. The RNA of the virus is used in the cell of the honey bee to make more copies of nucleic acid strands. The strands join and become DNA that can is used in the cell.
On one end of the RNA strands of the Black Queen Cell Virus, there is an arrangement called a cap structure. This cap structure in the RNA has many advantages for the virus, including accuracy in copy production, and resistance to changes in the RNA strands. These advantages to the virus are disadvantageous to honey bees. They are the reason the virus is able to have effects in both strong and weak honey bee colonies.
Why are Colonies Lost in Black Queen Cell Virus Infections?
The Black Queen Cell Virus is a lethal disease affecting mostly the queen larvae or pupae. For many beekeepers, this is particularly worrying. New queen bees are raised when the honey bee colony wants to swarm, or to replace an aged queen bee. Bees absconding from the beehive take the old queen with them or raise a new queen just before absconding. If the bees need a new queen bee and one cannot be raised in the beehive, it spells doom to the colony.
Modern beekeeping has led to a rise in demand of queen bees. Restocking of honey bee colonies, breeding and other hive management practices require occasional changes of the queen bee in a colony. Some beekeepers have specialized their beekeeping operations to meet the need for queen bees by fellow beekeepers. These beekeepers stand to lose a lot if the queen bees they are trying to raise are continuously lost to the Black Queen Cell Virus disease.
The ability of Black Queen Cell Virus to remain persistent in a beehive makes its control difficult. Though adult bees can be infected, they are asymptomatic. Even the queen bee can be infected, yet show no symptoms. Being a viral disease makes it hard to treat, though it is easily diagnosed through a Polymerase Chain Reaction test, which can be done after a colony displays its classic symptoms.
Beekeepers need to be able to look out for the symptoms to ensure an early detection, whereby taking control measures promptly will be more effective before the infestation becomes too heavy. Before embarking on a commercial apiary operation, beekeepers need to have some practical skills that will help them to detect and isolate bee infections as they manage their operations. Such information is available from the State Department of Agriculture, Agricultural training institutions, farmers associations and clubs all over the United States.
Can the Black Queen Cell Virus be Controlled Successfully?
The Black Queen Cell Virus can be controlled in most colonies if the beekeeper ensures that the colony is well fed, uses or introduces young uninfected queen bees in populous hives, and changes or rotates the combs every three to four years. Additionally, hives should be placed appropriately depending on the season. Hives should be placed in warm and sunny positions over the autumn, winter and spring periods. This will help keep colonies strong and remove extra stressors to the bees.
Every beekeeper is urged to familiarize themselves with the symptoms of the Black Queen Cell Virus. This is especially important to those involved in breeding queen bees. It is recommended that if a colony is suspected of being infected, cell starters or nucleus hives must not be used for breeding queen bees. They should not be sold or distributed. This helps in stopping the spreading of the disease through infected queen bees distributed to other hives and regions.
If the virus is detected in a queen bee breeding operation, the beekeeper should contact their local department of agriculture. This is to request to send in a sample for laboratory diagnosis and ascertain the presence of the disease. Use the information, tips and treatment options in this article to keep your beekeeping operation free from the losses caused by the Black Queen Cell Virus disease.
Have you ever dealt with the Black Queen Cell Virus in your beehives? Leave a comment below and let us know what your experience was like.