Honey Bee Viruses
Bees are critical pollinators that are essential for healthy ecosystems. However, all living creatures face health challenges. Honey bee viruses are significant threats to bee survival and productivity. This article explores some of the most common honey bee viruses, how they spread and what beekeepers can do to help their hives stay strong.
After many years of beekeeping, I have only witnessed a viral infection in my hives on one occasion. It makes you feel helpless because we simply can not cure the colony of a bee virus. Some diseases of honey bees have to be conquered by the bees themselves.
What are Honey Bee Viruses?
You won’t see a honey bee virus, these microscopic pathogens are too tiny for our eyes to see. Small they may be-but in severe cases a virus can affect the colony even to the point of causing death.
Unlike bacteria, viruses are not living organisms. They rely on the host bee’s cells to replicate and spread. They use the bees own body functions to grow.
Different from Other Bee Diseases
Viruses are different from other pathogens that harm bees. Unlike bacterial infections (like American Foulbrood) or fungal diseases like chalkbrood – viruses can not be treated with medications.
Bacteria or fungi can be killed with antibiotics. But, virus particles do not react to medication.
The key to hive management in the control of viruses is to prevent infections when possible and to keep colonies strong and healthy. We hope they can fight off the “sick bug” with their own immune systems.
Common Viruses Found in Honey Bee Colonies
Researchers have identified at least 19 different viruses that affect honey bees. They vary in threat level, castes of bees that are targeted and even different ages of bees are the victims. But, we have a few that are quite common.
- Deformed Wing Virus (DWV)
- Black Queen Cell Virus (BQCV)
- Sacbrood Virus (SBV)
- Paralysis Viruses – Israeli Acute Paralysis Virus (IAPV), Kashmir Bee Virus (KBV), Acute Bee Paralysis Virus, Chronic Bee Paralysis Virus (CBPV)
DWV – Deformed Wing Virus is the most widespread infections worldwide. It is one of the few bee viruses that presents obvious symptoms.
Wings of affected bees are shrunken and crumpled. The virus can be present in normal looking bees. It is very common in colonies with known varroa mite infestations.
BQCV – Black Queen Cell Virus is also found worldwide. It affects developing queen bees. After death the diseased pupae rapidly darkens causing the walls of the queen cell to turn dark brown-black.
Worker bees may be infected but show no symptoms. Infection is more common in colonies also suffering from Nosema disease.
SBV – Sacbrood Virus is very common in honey bee colonies. It affects both brood and adult bees but very young bee larvae are most susceptible. Young larva ingest virus contaminated food from nurse bees.
As the disease progresses, the skin becomes pale yellow and the head black. After death, the larvae do not pupate but becomes fluid filled sacs. Sacbrood can be a mostly seasonal problem – more often noticed in Spring Beekeeping.
Paralysis Viruses – There are several of these that are very similar and most share common symptoms. They are impossible to diagnose in the field and require a laboratory.
- IAPV-Israeli Paralysis Virus was found in Israel in 2004.
- KBV – Kashmir Bee Virus is found worldwide. It is the most virulent pathogen in laboratory conditions.
- ABPV – Acute Bee Paralysis Virus may occur in colonies for years with not apparent harm. You won’t know it’s them in most cases.
- CBPV – Chronic Bee Paralysis has the same symptoms as the others. It affects mainly adult bees.
One summer I had dozens of bees trembling at the front of the hive. No obvious poison nearby. I called the state apiarists and he said it is probably a virus. Nothing you can really do. If only a small number of bees are affected the colony will be okay. It was. But, that was scary!
Signs of Virus-Related Issues in a Colony
Honey bee viruses can have a variety of effects on individual bees and the whole colony. A few present visible symptoms that you may notice and others require lab diagnosis.
The most common symptoms to watch for are:
- Deformed wings – shriveled misshapen wings
- Shiny or hairless bodies
- Trembling or Paralysis – bees tremble, struggle to walk, unable to work
- Brood issues – dead larva resembling a fluid filled sac (Sacbrood)
- Dwindling colony population as bees die to young
- Aggressive or erratic bee behavior with no other explanation
- Poor queen performance
How Viruses Spread in the Colony
Just as in humans, viruses spread through individual-to individual contact. Honey bees share food and groom each other constantly. Viral particles can easily spread to many worker bees in a crowded hive.
External factors may contribute to virus spread too. Beekeepers using contaminated tools move from hive to hive can unknowingly spread viral diseases.
But, the role of varroa mites as disease vectors can not be overlooked. As these parasites feed on bees, they too transmit disease throughout the hive.
How Beekeepers Can Help Reduce Spread
Because honey bee viruses can not be cured in the conventional way, our goal must be to reduce their impact on colony health.
Prevention (where possible) is the first line of defense. Then, any measures that help reduce stress on the bees can help them be resilient against viral threats.
Key Strategies:
- Practice effective varroa mite control – test and use approved varroa mite treatments when needed
- Provide proper nutrition in times when natural food stores are low
- Practice good hive hygiene – sanitize hive tools and gloves to prevent disease spread. Rotate out old comb periodically to promote good health
- Reduce colony stress – prevent overcrowding, limit hive disturbances
- Support recovery to affected colonies – requeen a struggling hive, feed weak colonies, etc.
Treatment
There really is not treatment option for a honey bee colony with a viral infestation. Monitoring the hive’s conditions and assisting where you can (possible feeding bees sugar water if needed) if the best you can do. Strive to make sure the colony has the resources it needs and be ready to provide support if needed.
FAQs
Symptoms vary but deformed wings, greasy hairless workers and trembling or paralyzed bees at the hive entrance are some of the most common signs.
Researchers disagree with the number of known bee viruses varying from 7 or 8 to 19 or 22.
Yes, it is very possible for bees to be attacked by more than one virus at the same time.
Final Thoughts
While there is no guarantee that you can protect your honey bees from viruses, you can control some factors of bee health. Be careful when sharing frames between colonies where one might be unwell – same thing goes for tools and gloves. In many cases, a healthy colony will work through the virus and become healthy again.
Additional Resources
The Hive and the Honey Bee – edited by Joe M. Graham – Dadant Publishing