A mysterious disease that has reduced honeybee populations in Europe and the United States could be caused in part by a virus, according to research.

Scientists have discovered a characteristic pattern of cell damage in bees affected by colony collapse disorder (CCD), which suggests that a virus contributes to a condition that killed off more than a third of American honeybees in 2007-08.

CCD, in which worker bees suddenly disappear from their hive, was first reported in the US in 2006, and has since affected at least 24 states and parts of Canada. There have also been cases in continental Europe, and a few cases have been suspected in Britain though not confirmed.

The cause of the syndrome remains unknown. Potential triggers that have been advanced have included viruses, mites, fungal infections, pesticides, nutrient deficiencies and even mobile phone signals.

The research, by a team at the University of Illinois and the US Department of Agriculture, has indicated that a group of viruses called the picorna-like viruses are likely to be involved, though they may not be the only cause.

In a study published in the journal Proceedings of the National Academy of Sciences, scientists examined the way genes were switched on and off in the guts of bees from hives that later fell victim to CCD.

They found that compared with bees from unaffected hives, the CCD bees had abnormally high levels of fragmentation in a genetic chemical called ribosomal RNA (rRNA). This is used to build ribosomes, structures found in all living cells which manufacture proteins using genetic instructions written into DNA.

The fragmented rRNA suggests that the bees suffered from degraded ribosomes, in a fashion consistent with damage caused by picorna-like viruses. The scientists also found that bees from CCD hives had “more than their fair share” of infection with these viruses, according to May Berenbaum, of the University of Illinois, who led the study.

Picorna-like viruses, she said, in effect “hijack the ribosome” of bees to take over these protein factories, which are then used to make viral proteins, rather than those that the bees need themselves.

One of the viruses in the picorna-like group is Israeli acute paralysis virus, which has previously been suspected as the primary cause of CCD.

Dr Berenbaum said that while the viruses may not kill infected bees outright, the ribosome damage they cause may leave the insects especially vulnerable to other stresses and infections.

“If your ribosome is compromised, then you can’t respond to pesticides, you can’t respond to fungal infections or bacteria or inadequate nutrition because the ribosome is central to the survival of any organism,” she said. “You need proteins to survive.”

The research was published as the British Beekeepers Association released figures showing that nearly a fifth of Britain’s honeybee colonies died last winter. While the average loss of 19.2 per cent of colonies was better than the previous winter, when 30.5 per cent were lost, it remains worrying.

Tim Lovett, the association’s president, said: “The improved figure is very welcome but is way short of the 7 per cent to 10 per cent which until the last five years has been considered acceptable.

“It underlines the need for research into the causes and remedies for disease in order to ensure that our principal economic pollinator, the honey bee, can survive the onslaught of the threats it currently faces.”

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