Understanding the Deformed Wing Virus in Honeybees

Quick Overview

The Deformed Wing Virus (DWV) is a devastating ailment affecting honeybees globally, leading to wing deformation and other developmental issues that prevent bees from flying, thus hindering their ability to pollinate and produce honey. This virus is primarily spread by the Varroa mite, a parasitic mite that feeds on bees and acts as a vector for DWV and other diseases.

This article emphasizes the importance of bee health due to their critical role in pollination and human food supply. It discusses the causes of DWV, including Varroa mite infestation, lack of hive maintenance, colony stress, and starvation, particularly during winter when food reserves are low.

Symptoms of DWV are easily recognizable, such as wing and abdominal deformities, damaged appendages, and discoloration or paralysis of wings and legs. Diagnosis can be performed through various methods, including powdered sugar roll, alcohol wash test, sticky board method, and soapy water test.

Treatment primarily focuses on controlling Varroa mite populations, with options ranging from chemical interventions like acaricides and synthetic chemicals to natural treatments like essential oils and organic acids.

This article cautions against excessive use of harsh chemicals due to potential honey contamination and stresses the importance of measured, responsible treatment approaches to ensure bee health and survival.

What is the Deformed Wing Virus?

The deformed wing virus (DWV), also called the deformed wing disease is a viral infestation of the honeybee colony, affecting honey bees worldwide. The virus presents multiple symptoms and deformities and is named after the most obvious one suffered by bees: wing deformation. This deformity is induced in the pupa stage of a honeybee’s lifecycle. Their wings become shrunken and deformed among other often visible developmental deformities. It has become a global crisis for the bees and also for us as humans since our survival is tied to them.

It is caused by the infestation of Varroa mites in the colony of honeybees. They are responsible for a host of diseases in bees. They serve as a vector for many colony-threatening diseases like mosquitoes, including DWV. The major vector for this disease is the Varroa mite. Due to the severity of its effects, DWV is the most heavily investigated disease plaguing the beehives. Varroa destructors have been known to induce colony collapse if the virus goes untreated.

The deformed wing virus is an RNA virus. It is one of the 22 known viruses that can prove fatal for bees. Certain species of bees are more vulnerable to DWV like Apis mellifera, Bombus terrestris, etc. The first symptomatic bees of this virus were observed in Japan and a sample of this virus was isolated in 1980. Now this disease has spread worldwide. The virus is generally found in commercially reared bumblebees as well as pollen baskets.

If the bees have deformed wings, they will not be able to fly. If they cannot fly then they cannot pollinate or make honey. Honey is a food source for humans as well as bees. Without being able to fly from flower to flower collecting nectar they will make honey and eventually starve to death, not to mention the effects of reduced pollination of flora in the vicinity.

Causes of the Deformed Wing Virus

The deformed wing virus has been directly linked to Varroa mites, aka the Varroa destructor. There can be other factors involved with why or how a bee colony gets infected by it. Below we will discuss the main factors at play in the cause and spread of deformed wing virus.

1. Varroa Mites

The Varroa mite, also known as the Varroa destructor, is a parasitic mite. It attacks bees externally and feeds off of them. Being a parasite, it attaches itself to the body of bees and weakens its host by sucking its fat bodies.

Male Varroa mites are white. However, the adult female Varroa mites are reddish-brown. They are flat and shaped like buttons. They have eight legs. Generally, they are 1–1.8 mm long and 1.5–2 mm wide. Click here to check out the best treatment solutions for Varroa mites.

2. Lack of Maintenance

Most of the honey bees found today are in man-made colonies. These colonies require constant care and oversight. If you fail to perform regular inspections or ignore the signs of an infestation, then this disease can spread enough to destroy the whole colony. In some circumstances, it can lead to total colony destruction. If caught early, proper measures can be taken for the treatment and preservation of the colony.

3. Stress in the Colony

A colony that does not have a strong queen or the strength of numbers, can be more susceptible to diseases. Such colonies are described as weak colonies and they have a greater chance to succumb to Varroa destructors.

Generally, viral diseases in bees are latent but are sometimes exacerbated by stressful conditions. This can have serious consequences in terms of colony mortality.

4. Starvation

During winter, honey bees have low food reserves. If they get infected with mites, there is no way for them to recuperate as the Varroa mites live by feeding on their host body’s nutrients. Due to food scarcity, the bees will not be able to replenish themselves.

5. Spread

Occasionally, a hive may get a visit from a stray bee in search of food or warm shelter. That bee might be infected with the Varroa mite. Naturally, the native bees will attack and kill that stray bee, but the contamination with the infectious virus will inevitably spread to that colony too.

The intensity of the Deformed Wing Virus

The intensity of the deformed wing virus in honey bee colonies is due in large part to the reproduction of the Varroa mite inside the colony. These mites have a 10-day reproduction cycle. The female gets into the brood cells and once they are capped, the mites lay their eggs on the bee larvae. The bees and the mites have almost the same time frame for the development. The mites hatch as the larvae get ready to leave the cell after coming out of the pupa stage.

Symptoms of the Deformed Wing Virus

The deformed wing virus (DWV) causes a slew of problems for the bees. Its symptoms include:

• Deformation of the wing and abdominal area in adult bees.
• Damaged appendages.
• Decreased body size.
• Stubby and useless wings.
• Rounded, shortened, and bloated abdomens.
• Discoloring or the paralysis of the wings and legs.

The bees that show symptoms of deformed wing disease almost always have rather reduced lifespan. They usually live for a mere 48 hours and are expelled from the hive even sooner. It is part of the honey bees’ nature that a sick bee leaves the hive to die off to spare the hive from dead waste and disease.

Even when the mites are not present in the hive, the virus can persist in the bee populations of the colony as a covert infection. In such conditions, it is orally transmitted by worker bees.

The symptoms of the deformed wing virus are exclusively found in adult honeybees and are recognized quite easily. The mites suck on the fat bodies of bee larvae and the adults. This deprives them of the nutrients they badly need for their survival. The imbalance and deficiencies lead to disrupted bodily functions. The issues may include:

• Hormone and energy regulation problems
• Inefficient immunity
• Pesticide detoxification
• Severe lethargy

Sometimes, the mites on the adult bees get under the abdominal plates. It happens at the underside of the metasoma region side of the bee on the left side.

Studies show that mites found underneath the bee’s abdomen are generally there to feed. But most of the time, mites are visible on top of the bee’s abdomen in the mesosoma region. It is concluded that the mites visible on the upper side are not there to feed but attempting to transfer onto other bees.

When Varroa mites feed on the body of the bees, they leave open wounds. These sites are susceptible to disease and many viral infections. The Varroa mites are known to be vectors for about 5 to 18 incapacitating bee viruses other than the deformed wing virus. Certain species of honey bees such as European Apis mellifera, are entirely defenseless against these parasitic creatures.

Diagnosis of the Deformed Wing Virus

Varroa mites are very easy to diagnose by their distinct color. They have a reddish-brown color, eight legs, and oval bodies and they are visible to the naked eye. You can check for them manually in the hive. But sometimes they can hide on the bee’s bodies and in that case, you can perform simple tests to verify the presence of mites. A few of these tests are mentioned here.

1. Powdered Sugar Roll

For this test, take a sample of about 300 bees with the help of a 1/2 cup measuring cup. Place the bees in a jar that has a mesh lid of 1/8-inch after. Add 2 tablespoons of powdered sugar to the jar. Swirl the jar gently for a whole minute and then turn it upside down and shake it for two minutes. Do this over a collecting plate that will collect the mites as they will fall.

To quantify the results, count the bees and divide them by 3 to find the number of mites/100 bees. The benefit of doing a sugar roll test is that it prevents the death of sample bees.

2. Alcohol Wash Test

For the alcohol wash method, collect a sample of 300 bees using a 1/2 cup measuring cup. Then take alcohol with 70% or higher concentration in a jar and submerge the bees in it. Seal the jar with the help of a lid and give it good sake for about two minutes. Then take a 1/8-inch mesh screen and put it over a collection plate. Pour the mixture on it and count the number of mites. To quantify the mites, divide the number of mites, by 3 and you will get the no. of mites/100 bees. The alcohol wash test is considered the most effective method of diagnosis, but it kills all the sample bees which is quite brutal for the bees that are already plagued with death and disease.

3. Sticky Board Method

This test is the most humane method to diagnose Varroa mites. No bees are killed or hurt in this process. You can make a sticky board using petroleum jelly. Make sure to lay it on thick. Then place the board under a screened bottom board of a brood chamber. You can also use a 1/8-inch mesh screen for this purpose. Retrieve the board after a period of three days and afterward count the mites that are stuck on the board. Divide your count by three to find out the average rate of mites dropped per 24 hours. With this test, the results may take longer but no bees are harmed.

4. Soapy Water Test

It is an effective way to quantify the level of infestation. Take 300 bees from the colony. Add soapy water to a tube with a mesh top and put the bee inside. Now shake the tube and the mites will detach easily from the bodies of bees that fall through the mesh. Then use the following equation for the calculation:

Varroa destructor infestation rate = (number of mites / 100 bees counted)

Treatment for Deformed Wing Virus Disease

The most effective way to treat the deformed wing virus is by controlling the infestation of Varroa mites. These mites are the reason for DWV causing death as well as the destruction of whole colonies. Therefore, the best way to treat DWV is to control the population of Varroa mites within bee colonies. It is truly a nip-the-evil-in-the-bud kind of situation. The sooner you catch the infestation and treat it, the higher the survival rate of the bees.

Deformed wing virus requires chemical intervention for effective treatment. Another highly effective treatment method for it is to breed bees that are resistant to Varroa destructor mites. It is the simplest long-term solution for this problem.

Chemical Measures to Treat Deformed Wing Virus

There are many options for how Varroa mites can be treated on a commercial scale. Acaricides can be used in careful quantities. The appropriate usage of the acaricides will help slow down the resistance build-up against preventative treatments as well. But these chemicals have to be used at a minimum level as possible to avoid contamination of honey.

For the treatment of DWV, multiple options for synthetic treatments are also available.

Synthetic Chemicals for Deformed Wing Virus Treatment

Here is a list of synthetic chemicals used for deformed wing virus treatment:

• Pyrethroid insecticide, i.e. fluvalinate. They can be used as medicinal strips.
• Organophosphate insecticide, i.e. Coumaphos or the Check-mite. These can also be used as medicinal strips.
• Manley’s Thymol Crystal, was given as food for the treatment.
• Surgical spirit recipe with sugar, given as food for the treatment.

Natural Chemicals for DWV Treatment

Some naturally occurring chemicals can safely be used as a medicine for the treatment purpose of Varroa destructor, such as:

• Formic acid, i.e. Mite-Away delivered as vapor or medicine-soaked pads.
• Powdered sugar, talc, or any other available powders can be used too. But their grain size must be between 5 and 15 μm. These are delivered by sprinkling the substance on the bees.
• Certain essential oils can do the trick too. You may use lemon, mint, or even thyme oil as a mite treatment. For the delivery, dripping and pads both would work.
• Sugar esters, i.e. Sucrocide give good results in DWV treatment. They are applied by spraying the hive with its solution.
• Oxalic acid is also used for this purpose. It is generally used with trickling or vapor delivery methods. You may prefer to use towels soaked in an oxalic acid mixture.
• Mineral oils are also effective but you have to use edible-grade oils and deliver them to the hives periodically as vapor. You can also apply them directly on paper or cords and put them inside the colony.
• Natural hop compounds such as Hopguard can also be used. They are applied using the strip method.

Treatment Delivery

Generally, the treatments are delivered by spraying the chemicals onto the colony. You can also use vapors and trickle-down methods as medicine delivery systems. But when you are spraying for the mites, the chemical will get to the bees too. Due to the mites, a colony can already be weak and the added stress of chemicals in the mix can push them over the edge. The medicine can be given to the hive without causing these issues. You simply have to find moderate means. Here are a few suggestions:

• Deliver treatment using strips made of medicinal chemicals. Add a thin coating of sugar syrup or just a few drops of it on the strip and the bees will take to it.
• The dripping method can also help if the chemical water is not allowed to accumulate in the hive where it can fester.
• Aerosolizing the medicine is also effective, but only if all the bees get it when you are delivering medicine.
• Soak a towel in the medicinal solution and place it in the hive. The bees will chew on it, and rub their bodies against it.
• Edible treatment options can also be used, mainly because of the least side effects.

All of these are effective treatment delivery methods for the deformed wing disease. It is up to you to choose among the available options. Put the needs of the hive first and you will make the right decision.

The Downside of Using Harsh Chemicals for Treatments

Excessive use of harsh chemicals will contaminate the honey produced by the bees. This will lead to the contamination of our bodies by using bee’s honey as a food source. It can also affect the collective health of the colony. Too much treatment can create more problems and adversely affect the bees. To avoid these, foreseeable issues arising from the usage of chemical-based medicinal treatment, make sure that you only use the quantity necessary. Never over-medicate the beehive or under-medicate it so that the infestation does not clear. Always measure the extent of the problem before devising a treatment plan with appropriate medicine.

Bees are sensitive and prone to death and disease. They need proper invigilation to catch any signs of pests in the hive. If you catch it early, mild treatment routines will resolve the problem. But if you discover a full-blown infestation, you will have no choice but to go with severe treatment options using stronger chemicals. With the usage of strong dosages, you will have to weigh the effects it has on the bee and the honey.

Why are Bees Important?

Bees do not just make honey. In the process of collecting nectar, they pollinate all sorts of food crops. It has been estimated that bees are responsible for the pollination of one-third of our crops. Many farmers of fruits and vegetables raise beehives in the same vicinity to ensure a good harvest by effective pollination and it is all due to these busy little bees. A bunch of food crops require pollination such as avocados, soybeans, broccoli, celery, sunflowers for oil, cucumbers, cherries, cranberries, citrus fruit, peaches, kiwis, and melon. Many of these are a part of our daily diet and bees play a very important role in growing them. Most importantly, bees are essential for us to be able to enjoy almonds in our diet and blueberries on our pancakes.

About 80% of US crops depend on honey bees. Not just that, they are imported for animals too as they can also pollinate clover and alfalfa. It means that bees have valuable implications for the meat and dairy industry too. Besides being cattle feed, bee-pollinated crops are used in a huge range of manufactured food products using these ingredients. Cotton and flax are among those that depend greatly on bees for pollination.

We also enjoy a variety of non-food items produced solely by honey bees. They produce beeswax which is used for cleaning purposes and as an ingredient in many beauty products.

All in all, bees are necessary for humans in many ways. With the changes in the environment, climate shifts, and use of pesticides, the health risks for bees have increased dramatically. They are facing various crises that threaten their survival and ultimately ours. One reason for that is deformed wing disease.

Conclusion

Beekeeping is a demanding commitment and diseases like the deformed wing virus happen more often than we would like. The key is to think about the consequences before you decide to proceed with any kind of chemical intervention. With patience, care, and practice you can help your bees to survive any colony-threatening attacks. Simply remember to stay vigilant and make smarter decisions.

References

• https://www.theapiarist.org/deformed-wing-virus/ 
• https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/deformed-wing-virus 
• https://pubmed.ncbi.nlm.nih.gov/19909976/
• https://extension.psu.edu/viruses-in-honey-bees

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