Apis Iridescent Virus

Apis iridescent virus (AIV) is a DNA virus associated with "clustering disease" in the Asian honey bee (Apis cerana) in northern India and Kashmir. It takes its name from the blue-violet iridescent sheen seen in the internal tissues of an infected bee. In the European honey bee (Apis mellifera) no natural disease picture has been firmly established; if you see similar symptoms, the cause is most probably something else.

What is it?

AIV is a relatively large DNA virus from the iridovirus group. It was first described in the 1970s in Kashmir and northern India, from diseased Asian honey bee colonies. It was associated with a disease seen in this region during the summer months.

The word "iridescent" means shimmering with changing colours. This sheen is not seen on the outside of the bee but in the fat body and internal organs when the bee is opened and examined; it is caused by virus particles accumulated in a crystalline arrangement in the tissues.

The disease picture in the Asian honey bee

• Bees become inactive and unable to fly
• They form small, motionless clusters on the comb or on the ground (hence "clustering disease")
• Bees are seen crawling in front of the hive
• In severe cases the colony may die out
• A definitive diagnosis is made from the iridescent appearance of the tissues and by demonstrating the virus in the laboratory

How the virus spreads between colonies has not been sufficiently studied.

The situation for the European honey bee

The European honey bee has been infected experimentally with the virus in the laboratory; however, no widespread disease picture under natural conditions has been firmly established in this species. For beekeeping in Türkiye it should not be regarded as an everyday threat.

A study published in the USA in 2010 had linked another iridescent virus, together with Nosema, to colony collapses. In later assessments this finding was criticised on methodological grounds and was not confirmed.

Common misconceptions

• It is not true that AIV causes disease "especially in the European honey bee" and "in larvae"; the known picture is in adult Asian honey bees.
• No iridescent spots form on the outer surface of the bees; the sheen is in the internal tissues.
• What has been described is not "hyperactivity" but, on the contrary, inactivity and clustering.
• Recommendations of a medicine or a "resistant local breed" against this virus have no scientific basis.

If you see sluggish, crawling bees in a colony

In the European honey bee, inactive, flightless, clustering or crawling bees have far more likely causes:

What to do

1. Mark the colony showing symptoms; do not move frames or bees from this hive to other hives.
2. Do a varroa count; if it is high, treat with an authorised medicine, following the label instructions.
3. Find out whether there has been spraying in the area; in a sudden mass death, keep a sample of dead bees.
4. Check the colony's honey and pollen stores.
5. If no cause can be found, send a sample of adult bees to the laboratory via the official veterinary service / local agriculture authority.

There is no authorised medicine against bee viruses; antibiotics do not work and leave residues in honey. Protection comes from strong colonies and regular varroa control.