We don’t know if the virus is the causal agent, but a recent Science paper used a metagenomics approach to find that bees from colonies that have collapsed are infected with a virus (and it’s the same virus in different colonies). Essentially, the researchers ground up bees, sequenced the whole mess, and using previous genome data, subtracted out the genome of the honey bees.
What was left were some bacterial symbionts, and in the failing colonies, a virus. From the BBC:
But in 2004, beekeepers began seeing and reporting a new and serious phenomenon, in which entire colonies would desert their hives, leaving behind their brood and stocks of food – a syndrome that was later labelled Colony Collapse Disorder….
“The genome of the honeybee had just been completed,” noted Diana Cox-Foster, an entomologist from Penn State Universiity. “So it was possible to do the (genetic) sequencing and then eliminate the genetic material of the bees.”
The scientists’ trawl revealed a diverse cargo even in healthy colonies. Eight types of bacteria appeared to be present in all bees, suggesting they perform some function useful to their hosts.
The researchers also found genes from parasites, fungi, and viruses, in both healthy hives and in those which had undergone collapse. But IAPV [Israeli Acute Paralysis Virus] only appeared in samples from CCD populations….
As its name would suggest, IAPV was first identified in Israel, but the symptoms it produces in bees there are quite different.
Whether this is down to a small genetic difference in the virus between continents, or whether IAPV is acting in concert with different environmental factors, is an open question.
Also open is the question of how the virus arrived in the US. One finger of suspicion points to Australia, from where the US began importing honeybees in 2004 – the very year that CCD appeared in US hives.
The researchers found IAPV in Australian bees, and they are now planning to go back through historical US samples to see if the Antipodean imports really were the first carriers.
If they were, the US might consider closing its borders to Australian bees.
If IAPV does turn out to be a major factor causing CCD, there may be little that scientists or beekeepers can do about it.
“We’re unlikely to come up with a treatment for viruses in bees,” said Dr Pettis, “and so beekeepers are likely just to have to keep the other things that might affect CCD, such as mites, under control.”
While a ‘cure’ probably isn’t feasible, a simple PCR screen could be used to determine which colonies are sick, and those colonies could be destroyed (and, obviously banned from importation and transport).