A virus that is the most likely cause of a mysterious disease devastating the bee population in the United States has been found.

Honey bees in 50 to 90 per cent of all commerical hives in the US have vanished owing to colony collapse disorder (CCD).

The disease, which was first recognised as a major problem last year, raised fears that with the national shortage of bees, about £8 billion worth of crops would not be pollinated. Bees are vital to the production of more than 90 crops, including almond, alfalfa and sunflower seed, apple, cherry, melon, and berries.

Scientists trying to understand the cause of the disease have now linked it to the Israeli acute paralysis virus (IAPV), which was first identified in 2004.

With CCD, hives empty of adult bees in a matter of days, leaving the honey and pollen behind along with the queen and a handful of newly hatched bees. CCD caused the disappearance of hundreds of millions of bees in 22 states at the end of last year.

Researchers identified the virus by carrying out genetic studies of infected and uninfected bees, which allowed them to pinpoint genes originating from viruses.

Microbial agents were suspected as the cause of the disease because it was found that bees moved back into hives that were irradiated and cleared of CCD. Several viruses were identified but only one, IAPV, was associated with all the relevant samples.

IAPV symptoms include shivering wings and progressive paralysis, with the bees dying outside the hive. Though CCD symptoms differ, it was thought there could have been a mutation of the virus to affect US bees.

The findings support suggestions that the disease could have been introduced to the US through imports of bees from Australia, which only started in 2004, having been banned by law in 1922. Similarly, another potential source was royal jelly from China, used to feed queen bees.

Researchers were confident that they had found a solid link between the disease and the virus but said it was too early to be sure it was the cause. The study, reported in the journal Science, was carried out by several institutions, including Pennsyl-vania State University and Columbia University. Ian Lipkin, of Columbia University, said: “Our next step is to ascertain whether this virus, alone or in concert with other factors such as microbes, toxins and stressors, can induce CCD in healthy bees.

“We have a lead, now we can begin to follow. We can use it as a marker and we can use it to investigate whether it does in fact cause disease.”

Dr Pettis, of the US Department of Agriculture’s Bee Research Laboratory, added: “This research gives us a very good lead to follow but we do not believe IAPV is acting alone. Other stressors are likely to be involved.”

Contributory factors to the collapse of colonies being investigated include parasitic mites, pesticides, poor nutrition and the stress of being moved in trucks from region to region as they are rented out to pollinate crops.

Researchers said that their findings helped to discount alternative theories about the source of infection, such as radiation from mobile phones and the introduction of genetically modified crops.

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