Farmed Honeybees Transmit Disease to Wild Bumblebees

A study of wild bumblebees has revealed that two of the same diseases common in managed honeybee colonies are now widespread in wild bumblebee populations around the UK, revealing that diseases can spread from honeybees to bumblebees.

Bumblebees have been found with deformed wing virus (DWV) and the fungal parasite Nosema ceranae across England, Scotland and Wales, according to a team of researchers who published their findings in the journal Nature.

"We have known for a long time that parasites are behind declines in honeybees," Mark Brown a professor from Royal Holloway, University of London, said in a statement. "What our data show is that these same pathogens are circulating widely across our wild and managed pollinators. Infected honeybees can leave traces of disease, like a fungal spore or virus particle, on the flowers that they visit and these may then infect wild bees."

The strains of DWV and N. ceranae were the same when analyzed in managed bee colonies and in wild insects, the researchers said. They suggest that managed honeybee colonies are the source of the pathogens observed in the wild bee populations.

"One of the novel aspects of our study is that we show that deformed wing virus, which is one of the main causes of honeybee deaths worldwide, is not only broadly present in bumblebees, but is actually replicating inside them. This means that it is acting as a real disease; they are not just carriers," said researcher Matthias Fürst, also of Royal Holloway, University of London.

"Wild and managed bees are in decline at national and global scales," he said. "Given their central role in pollinating wildflowers and crops, it is essential that we understand what lies behind these declines. Our results suggest that emerging diseases, spread from managed bees, may be an important cause of wild bee decline."

The researchers found both DWV and the fungal parasite were present in honeybees and bumblebees sampled at 26 sites across the UK. They report that their study provides the first epidemiological evidence of these bee ailments across the UK. The researchers contend that urgent action is needed to reduce the threat of emerging diseases in both wild and managed bee populations.

"National societies and agencies, both in the UK and globally, currently manage so-called honeybee diseases on the basis that they are a threat only to honeybees," Brown said. "While they are doing great work, our research shows that this premise is not true, and that the picture is much more complex. Policies to manage these diseases need to take into account threats to wild pollinators and be designed to reduce the impact of these diseases not just on managed honeybees, but on our wild bumblebees too."