Apis iridescent virus takes its name from the colour sheen that appears in tissue samples under heavy infection.

The origin

It was described in Apis cerana in Asia, in connection with a condition in which colonies lost the ability to fly and collapsed.

Affected bees crawled together in front of the hive and could not fly; the colony disappeared in a short time.

The association with other factors

In those outbreaks other pathogens were usually found as well, including nosema.

That makes it difficult to establish the role of this virus in isolation — a problem common to many bee viruses: they are rarely found alone.

Significance for the western honey bee

Limited. The virus has mainly been described in Apis cerana and plays no practical role in ordinary beekeeping with the western honey bee.

That could change — species and pathogens move — but at present no measure follows from it.

Diagnosis

Laboratory only. Crawling bees unable to fly occur with nosema, with tracheal mites, with poisoning and with several viruses; the symptoms do not distinguish.

What is practical

With a colony that suddenly loses its ability to fly, check the known causes:

• Poisoning — especially if several colonies are affected at once
• Varroa and the viruses it transmits
• Nosema
• Tracheal mite

Collect dead bees, photograph, record date and location, and have them tested. Without samples nothing can be established afterwards.