What is the Kashmir Bee Virus (KBV)?

The Kashmir Bee Virus (KBV) is one of the diseases that affect honey bees. Just like any other viruses and pathogens, it spreads swiftly in honey bee colonies. This is attributable to the fact that honey bees are social insects and thus viruses will spread due to close contacts among the honey bee, sharing food and clustering during periods of confinement.

Honey bees instinctively reduce disease risk through a combination of behavior, that is, social immunity, or individual immune function. The effectiveness of honey bee social and individual immunities has a direct effect on the overall health or state of the colony.

The parasitic mite referred to as Varroa compromise the heath of the honey bee colony. The parasites suppress the nutrient levels, cripple individual immunity and spread viruses. A lot of future research will be geared towards a better understand of the dynamics of nutrition to immunity relationship with respect to the level of stress, seasons or time of the year or colony demographics.

The Kashmir Bee Virus is common globally and is regarded as one of the most virulent among all viruses that affect honey bees. One of the things that make it so different from other viruses, is the fact that it does not cause infection when developing honey bee ingests it. It also persists in its dormant state in adult and developing bees, and will never show any clear symptoms. Nevertheless, the virus becomes fatal when transmitted by Varroa mites, and will affect all forms of the honey bee life cycle. And it displays no apparent symptoms. The virus can kill colonies even when there is a moderate level of mite infestation, just like with the Acute Bee Paralysis Virus (ABPV).

Honey Bee Immune System

Colonies of honey bees and other social insects rely on group behaviors and individual immunity for survival. These help counter viruses and diseases that pose a serious risk to their wellbeing. It helps the insects respond to pathogens and parasites.

Social Immunity

Social immunity simply refers to the collective defense employed by honey bees and other social insects against parasites and pathogens through their collective effort. What this means is that each individual does a small task that contributes to an overall wellbeing of the colony. This helps reduce the spread of these parasites and pathogens.

Worker bees play the role of removing dead adult bees and diseased or parasitized bees from the colony. Adults with high pathogen loads die outside the beehive thus helping secure the entire colony from further infection.

Thermoregulatory behavior is also used by honey bees to keep the colony safe. This helps counter pathogens that are sensitive to heat. For instance, chalkbrood fungus (Ascosphaera apis).

Apart from group behavior; honey bees also collect propolis or plant resin. This is used to make a water and airtight environment that helps keep out viruses and fungus. The compounds in propolis help boost the immunity of the bees. The other ingredients contained in propolis inhibit Varroa mite populations through their miticidal properties.

Individual Immunity

Honey bees also rely on individual immunity when it comes to defense against pathogens and diseases. Their first line of defense is the exoskeleton cuticle that acts as a physical and chemical barrier to pathogens. The membrane lining the digestive tract is also a first line of defense for honey bees. These prevent pathogens from entering the body or sticking to the body surface. The cellular and immune response acts a second line of defense in case the pathogens manage to get past the first line of defense.

The honey bee innate immune response involves recognition of the structural patterns on the surface of pathogens. This is attained through the action of the Pattern Recognition Receptors (PRRs).  These are encoded proteins that function as agents of defense against microbial infections in bees, just like the blood cells in humans. They are broadly referred to as antimicrobial peptides (AMP). These include abaecin, defencin, hymenoptaecin, and apidaecin.

Some of the pathways that have been experimentally identified to control the action of AMP genes in response to a virus infection include: Toll, JNK, Imd, and Jak-STAT. Other studies noted that honey bees that have been infected with the Acute Bee Paralysis Virus do not activate cellular immune or humoral responses. In similar studies carried out recently, it showed various range of trigger pathways in the cellular innate immune response when the honey bees are infected with Israeli Acute Paralysis Virus (IBPV).

Kashmir Bee Virus Diagnosis

The Kashmir Bee Virus is closely related to the Acute Bee Paralysis Virus when analyzed genetically and serologically. The two viruses were pointed out to be key contaminants during the study of the Chronic Bee Paralysis Virus (CBPV) transmission. It is believed that both viruses must have originated from the same ancestor and taken different evolution paths in secluded geographic regions. The viruses can co-infect the same honey bee colony and affect the same bee, making the situation much worse.

Both KBV and ABPV might be closely related but the two can be readily differentiated through laboratory testing. The complex tests undertaken show the VP4 proteins of the two viruses to be serologically different. There exist significant differences between the two viruses when the genome is evaluated. This is a key area containing the primary and secondary RNA structures that help the experts distinguish the virus.

Molecular testing and evaluation are key strategies that help during the diagnosis of the Kashmir Bee Virus in honey bee colonies, Apies mellifera. Some complex procedures that involved serology, that is, chemiluminescent Western blotting, and or nucleic acid amplification, that is RT-PCR or reverse transcription-polymerase chain reaction, prove to be effective. Alternatively, it is possible to detect viral infection, in some situations through Coomassie blue staining of SDS-PAGE gels.

With laboratory conditions, Kashmir bee virus can easily be differentiated from acute paralysis virus. The various tests undertaken target the viral RNA composition. This involves using the monospecific antisera raised versus putative picornavirus such as VP4 polypeptide.

The laboratory tests require a tiny amount of material from the Western honey bee. Therefore, the examination of a single bee is sufficient for the ascertaining the presence of a number of pathogens or viruses.

The Kashmir Bee Virus can be transmitted through multiple routes in honey bee colonies. Any traces of KBV detected in brood food, royal jelly, faeces, honey, or pollen will mean the virus was transmitted orally through infected food sources in the honey bee colony. More so, any of the virus traces detected in Varroa mites or their salivary secretions, imply the parasite can be an agent or transmitter of KBV. Nonetheless, further studies are yet to confirm the effective role played by varroa mites when it comes to the transmission of the virus whether physically or biologically. The mites play a big role when it comes to transmitting viruses in honey bees. As a matter of fact, beekeepers are advised to control Varroa mites as a measure of countering most of the viruses that grapple beekeeping.

Symptoms of the Kashmir Bee Virus

The Kashmir Bee Virus can be identified through a number of signs and symptoms.

First category:

  • Trembling of adult bee wings and bodies. The bees are unable to fly and can be seen crawling on the ground or on plant stems.
  • Sick and weak bees cluster together.
  • Bees with a bloated abdomen, leading to dysentery. They will die within a very short time after displaying symptoms.

Second category:

  • Greasy adult bees that are hairless and can fly but within a few days, can no longer fly. They begin to tremble and soon die.

Some or all of these signs may be seen within the same honey bee colony. Colonies that are severely affected, especially the strongest quickly begin to lose adult workers. Eventually, this leads to a colony collapse. Initially, signs may not show and later begin to manifest when it is too late. Thus, regular monitoring of the honey bee colonies can never be emphasized enough. Beekeepers should be on the lookout for any sign that appears out of the norm. The overall behaviour of the colony can act as a guide.


Kashmir Bee Viruses normally target the digestive system and will get into the system through oral ingestion of food. The virus infects the epithelial cells located within the mid gut. These cells are continuously replaced and are normally secured by membranes and filters that keep off the pathogens from gut tissues. Nosema apis and Nosema cerana are the parasites that infect the gut area, creating lesions in the epithelium. This allows harmful viruses such as Kashmir to penetrate to the haemolymph and destroy some other cells in the honey bee body.

Interestingly, an external parasite such as Varroa destructor directly feeds on bee haemolymph. It inflicts openings on the bee cuticle that pave way for viruses to enter. Remember, most virus infections will never result in an infection if ingested orally. However, it takes a few virus particles to cause an infection if directly injected to the haemolymph. Many viruses that affect honey bees are transmitted by Varroa mites.

Some viruses like sacbrood, have been identified in Varroa mites through lab tests. However, Varroa mites do not transmit the virus directly. Other tests have shown Kashmir bee virus multiplies in Varroa mites.

Control Measures for the Kashmir Bee Virus

Inspecting beehive frame for the Kashmir Bee Virus

Kashmir Bee Viruses can persist in normal and healthy colonies without notice. They later explode in times of stress. Most of the honey bee viruses are damaging combined with other stressors such as Varroa or Nosema. Therefore, continuous and integrated management of these triggers can help minimize the virus.

Regular inspection of honey bee colonies is encouraged. The beekeeper should be familiar with the signs and symptoms that can help tell whether there is a viral infection or not. Some of these include colonies being slow to build up, sporadic brood patterns that indicate the brood has been removed. If disease is suspected, a sample should be taken and diagnosis done.

The Kashmir Bee Virus does not have a specific treatment. Thus, beekeepers should adopt recommended measures for control and minimizing viruses in honey bee colonies. Beekeepers can reduce viral spread and lessen exposure to other triggers like parasites, pesticides, and nutritional deficiency. Additionally, uncontrolled populations of Varroa mites are the main agents of transmission of viral infections.

1. Nutrition and Immunity

Nectar and pollen are ideally sufficient for sustaining honey bees since they contain the required nutritional requirements. The bees normally collect pollen and nectar in excessive amounts during peak seasons and is stored in preparation for periods of dearth, in the form of beebread and honey.

The main source of energy for all the stages of the honey bee is the honey, ideally rich in carbohydrates. Pollen on the other hand provides protein and other nutrients that are essential for immunity, growth, and brood rearing.

The type of feed taken by the honey bees will affect their immunity and directly affects how the colony will respond to a virus such as the Kashmir Bee Virus and others. The protein contained in pollen is rich in amino acids that help during the production of peptides in immune pathways. Additionally, the carbohydrates sourced from honey helps pump energy for metabolic processes that impact cellular immune reactions and innate humoral reactions. It is also a source of secondary plant metabolites that boast antimicrobial properties.

Therefore the first defence against any viral attack is the honey bee nutrition. Varro mite infestation can adversely compromise colony response to pathogens. Sufficient nutrition should be availed throughout the various stages of the honey bee since it helps raise a stronger colony that can overcome parasitic and viral invasion. For instance, worker bees that are parasitized during their developmental stages emerge with low protein a level that is impossible to boosts even if the sufficient pollen is provided. This also applies to the pupae stage of the honey bee. The parasitic infested pupae end up with lower protein content, low amino acid levels, and significantly lower weight on emergence when compared to healthy pupae.

Therefore sufficient and good quality feed should be provided to the honey bees as the first line of defence against the Kashmir Bee Virus. Once this is done the rest becomes much easier to handle. However, Varroa mite control should be a priority alongside nutritional considerations. Remember, abundant resources during peak seasons also stimulate the Varroa mite population growth as well. Therefore, if not considered your effort might be counterproductive.

The mites have developed mechanisms of survival even during the tough times. For instance, the Varroa mite population increases substantially during fall when the brood is at its minimum. The parasites also develop faster inside the drone cells. These cells are chosen since the cells are larger and their post capping stage takes 15 days which is much longer than that of worker bees (11 days). This therefore means the mites are able to produce more offspring for each cycle.

2. Minimize Colony Transmission

The beekeepers should reduce the spread of the virus between colonies since viral infections are higher when there is a higher number of a honey bee colony.

This can be achieved by:

  • Reducing the number of honey bee colonies in each apiary.
  • Strategic placement of beehives to avoid the drift of infected honey bees. Spacing honey bee colonies farther apart with hives facing different directions.
  • Avoiding the use of frames from infected colonies other honey bee colonies. Any colony portraying symptoms of a viral infection should be avoided.
  • All hive tools and equipment should be cleaned with alcohol after inspection.
  • Feed honey bees with high-quality feed.


3. Cultural Solutions

Cultural solutions can help keep off the Kashmir Bee Virus and other viruses. The use of Varroa mite resistant stocks of honey bees will help. Some of the resistant stocks include the Russian honey bee. Other stocks that are Varroa sensitive and the ankle-biter or leg-chewer stocks can resist KBV and other viruses. These honey bee stocks have also shown an ability of suppressing viral populations.

4. Minimize Pesticides Exposure

Beekeepers should minimize exposing their honey bees to pesticides. First off, they can register with their local authorities so that they are informed when a pesticide spray is about to be carried out within their area. It is also important to meet with local growers within the locality so as to deliberate on ways of minimizing pesticide use.

5. Mechanical Solutions

a. Old Honey Combs Removal

Viruses and other contaminants of the hive build up over time on wax combs, and if not removed it can lead to spread of viruses and diseases. Therefore, old honey combs should be rotated regularly or removed completely. As a general guide, replace at least ⅓ of the honey frames in each colony every year. Any old combs that have been removed should be destroyed.

b. Propolis Accumulation

It is usually accumulated on hive entrances and other openings that exist in the beehive. Bees have been using propolis for the longest time and beekeepers have learned about its effectiveness in countering honey bee viruses and diseases. The beekeeper can apply the propolis solution on the interior of honey bee hives. Alternatively, you can encourage honey bees to deposit propolis within the beehive through a number of ways. First off, scrape off the interior part of wood used to build hives so as to make it rough. This will encourage honey bees to deposit propolis. Secondly, the use of a cotton cloth as inner cover will encourage the bees to fill it up with propolis.

6. Chemical Solutions

Essentially ,there are no specific chemical treatments for the Kashmir Bee Virus, just like many other viruses in honey bee colonies. Fortunately, certain natural chemicals that may not be available commercially, will help curb the spread of the virus. These substances have been identified by researchers since wild bees have been using them for many years. Others have been discovered through trial and error and have proven to work.

They include the following:

a. Thymol treatment

Thymol is a potent ingredient that helps counter most of the viruses that affect honey bee colonies. Apiaries should be treated with 0.16 ppm thymol. This has proven to to reduce levels of Kashmir Bee Virus. It also helps counter acute bee paralysis (ABPV). This can be applied on just emerged honey bees then returned to colonies. Unfortunately, thymol treatment may not guarantee consistent results.

b. Propolis solution

Propolis is one of the naturally products used by honey bees as disinfectant. It has been tested and confirmed to boost the immunity of honey bees and inhibits virus spread in honey bee colonies. Propolis solution can be applied to the beehive and the bees as a way of countering the Kashmir Bee Virus and other viruses.

c. Fungal extracts

Fungal extracts from two major species, that is, Ganoderma retinaculum and Fomes fomentarius can help reduce levels of the Kashmir Bee Virus and other viruses in honey bee colonies.


You can prevent colony losses from Kashmir Bee Virus through proper control and management of Varroa mites. The honey bee is regarded as an essential pollinator for plenty of agricultural crops and other wild plant species globally. Just like any other agricultural-based activity, beekeeping as a venture is important in a lot of countries, not just because it is required for pollination services for fruits and seeds production, but also because it provides honey bee products that are exported to other countries.

The Kashmir Bee Virus is not so common or prevalent in Australia or the United States. Nonetheless, in instances where it is endemic, it is rarely reported within Europe, just like most other dicistroviruses. The virus usually remains dormant within healthy colonies until some triggers or stress factors stimulate viral multiplication leading to death of the honey bee colony.

Various studies have pointed out that Kashmir Bee Virus infection will occur at the different developing stages of the honey bees, without any clear or identifiable virus symptoms. The disease has been so common over the last decade. In fact, it is perceived as a potentially lethal virus that has become more important and requiring urgent action. It is particularly categorized within the class of viruses that are linked to colony collapse in colonies infested with the Varroa mite destructor.

About Michael Simmonds

Michael Simmonds is a beekeeper from the United States, with over 20 years of experience in the field. He developed a passion for beekeeping at a young age and started his own apiary when he was just 15 years old. Over the years, he honed his skills and gained extensive knowledge about honeybee biology and behavior.
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