Honey bees are challenged by viruses that impact their health and survival. While bees have natural defenses, large viral loads can overwhelm their immune systems causing illness and death. Understanding common bee viruses, where they come from, and how to manage them is key for supporting hive health.
What are honey bee viruses?
Viruses are infectious agents made up of DNA or RNA that can only reproduce inside the cells of living organisms.
Honey bee viruses damage tissues and cells, impacting bee development and lifespan. Infected bees often have stunted growth, deformed wings and abdomens, discoloration, trembling, paralysis, and early death.
Where do honey bee viruses come from?
Honey bees can contract viral infections a number of ways, including through:
Varroa mites: When Varroa mites puncture bees to feed on their blood (hemolymph), they can transmit viruses like Deformed Wing and Acute Bee Paralysis.
Contaminated food: Viruses can be passed via infected pollen, nectar, and bee bread (mixture of pollen, honey and saliva) that is stored in the hive.
Drifting bees: Forager bees from other hives can “drift” into a new hive, potentially carrying viruses. Bee drift happens when bees from one colony enter the hive of another and are accepted as a member.
Shared equipment: Used beekeeper tools and equipment may harbor viruses if not properly sterilized.
Strong hive populations with lower mite infestations generally have better viral resistance. Stressors like pesticides, poor nutrition, and travel from pollination services can suppress bee immunity and spur outbreaks.
Common honey bee viruses and symptoms
Deformed Wing Virus (DWV)
The most widespread viral infection, DWV causes shriveled, malformed wings and swollen abdomens in infected bees. Transmitted mainly by varroa mites, bees with DWV only live a few days after emerging from its cell due to its inability to fly and forage.
Black Queen Cell Virus (BQCV)
BQCV affects queen development in capped (covered with wax) brood cells, killing the baby queen before she emerges. Infected pupae turn yellow and then black after death. BCQV is thought to be transmitted by nurse bees feeding the queen larvae infected brood food.
Sacbrood Virus (SBV)
SBV leads to failure of brood development, with larvae dying soon after capping. Infected larvae change from pearly white to yellowish, then grayish black, eventually drying out and becoming a dark brown gondola-shaped scale on the cell bottom. Sacbrood is highly contagious and transmitted by various means.
Chronic Bee Paralysis Virus (CBPV)
The symptoms of CBPV in adult bees include trembling, black hairless abdomens, and the inability to fly, often crawling on the ground before dying. Bees may also have bloated abdomens and dislocated wings. CBPV can cause colony collapse and is spread predominately by Varroa mites.
Acute Bee Paralysis Virus (ABPV)
Primarily spread by Varroa, ABPV appears suddenly in the bee colonies. Bees with ABPV are sluggish, tremble, and experience paralysis. Infected bees die outside the hive, after being ejected by the healthy worker bees. Infected pupae turn pale yellow then black.
Israeli Acute Paralysis Virus (IAPV)
Related to ABPV, CBPV, and another virus called Kashmir Bee Virus, IAPV manifests suddenly with bees unable to fly, crawling and trembling before dying outside the hive. Collapsed colonies may show scattered dead bees with few dead bees inside hives.
Bee Virus Treatment and Prevention
While there are no direct treatments for viral infections, beekeepers use integrated pest management to protect hive health:
- Varroa mite controls: Minimizing mite levels is paramount to reduce viral transmission
- Hygienic stocks: Beekeepers may select virus-resistant honey bee stocks like Italians and Russians
- Proper nutrition: Well-nourished bees better withstand viruses
- Hive sanitation: Best practices for beekeepers include replacing old disease-prone honeycomb every few years and sterilize equipment after using
- Stress reduction: To reduce distress, beekeepers avoid moving hives unless necessary, limit the number of times they open a hive, and join weak colonies with stronger ones.
Viruses are a constant threat for bees and beekeepers. But proactive management focusing on mite control, hygiene, nutrition, and reducing stress can tip the scales in the bees’ favor for healthier, more productive colonies.
