Eleven species of wild pollinators in the United States have turned up carrying some of the viruses known to menace domestic honeybees, possibly picked up via flower pollen.

Most of these native pollinators haven’t been recorded with honeybee viruses before, according to Diana Cox-Foster of Pennsylvania State University in University Park. The new analysis raises the specter of diseases swapping around readily among domestic and wild pollinators, Cox-Foster and her colleagues report online Dec. 22 in PLoS ONE.

Gone are any hopes that viral diseases in honeybees will stay in honeybees, she says. “Movement of any managed pollinator may introduce viruses.”

A pattern showed up in the survey that fits that unpleasant scenario. Researchers tested for five viruses in pollinating insects and in their pollen hauls near apiaries in Pennsylvania, New York and Illinois. Israeli acute parasitic virus showed up in wild pollinators near honeybee installations carrying the disease but not near apiaries without the virus.

In domestic honeybees, such viruses rank as one of the possible contributors to the still-mysterious malady known as colony collapse disorder that abruptly wipes out a hive’s workforce, Cox-Foster says.

Now she and others are looking at what the viruses do to wild pollinators. Preliminary results of ongoing lab tests show some disturbing effects, Cox-Foster says. “Is this part of the reason why we’ve seen the decline of native pollinator species in the U.S.?” she muses.

Surveys show that wild bumblebees, for example, are dwindling in numbers, and the new study raises further concerns. “We recognize that those viruses likely pose a major threat to wild bumblebees,” says Sarina Jepsen of the Xerces Society, an invertebrate conservation group in Portland, Oregon.

One of the most interesting results in the study is the detection of deformed-wing virus and sacbrood virus in pollen carried by foraging bees that weren’t infected themselves, comments Michelle Flenniken of the University of California, San Francisco, who has studied bee viruses but was not involved in the new work.

Healthy foraging insects carrying virus-laden pollen are one of the pieces of evidence that Cox-Foster and her colleagues use to argue that pollen by itself can transmit viral infections. “Knowing that viruses are found in and can be transmitted from pollen is an important finding,” says Flenniken.

This raises concerns about possible virus transmission through the 200 tons of honeybee-collected pollen used to feed bumblebees in bee-raising operations worldwide, Cox-Foster says.

Image: A wild bee (the bumblebee, Bombus vosnesenskii) and a honey bee forage together on a sunflower. Sarah Greenleaf/UC Berkeley

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