Study Links Honeybee Deaths To Fungus, Insect Virus
There's a lot of buzz in the scientific community about a new study linking the collapse of honeybee colonies to a fungus and insect virus first seen in Asian bees.
"Our data suggests that these two pathogens interacting together may be playing a pretty big role," says study author Robert Cramer of Montana State University. The Nosema ceranae fungus can sicken bees when they ingest spores, and Cramer explains that the occurrence of both the iridescent virus and the fungus at the same time seems to be the problem.
The findings don't crack the case, though: "Not even close," says Cramer. But he hopes his study, published this week in the online journal PLoS One, offers an important clue.
How A Hive Collapses
Beekeepers have been reporting troubles with collapsing colonies for more than six years. The story is almost always the same: The population starts to dwindle, and then there's a rapid disappearance of bees, sometimes within just days. Pennsylvania beekeeper Dave Hackenberg recalls the experience from 2004 of checking on a hive one morning after noticing a loss of bees. He estimates there were several thousand in the hive.
"But by 1 or 2 o'clock in the afternoon, nobody was home," Hackenberg says. "They just totally disappeared."
Colony collapse disorder has been linked to 40 percent to 60 percent of disappearing beehives over the past six years. In a typical year, a beekeeper may lose up to a third of bees from extreme weather conditions, so some die-off is normal. "But this is more than some beekeepers can handle," Hackenberg says.
Prior studies have also linked colony collapse to different viruses and pathogens, but one researcher says viral sicknesses may be just one of the threats that bees face.
"I think that the data so far from lots of studies -- including from this one -- shows that the bees get very sick," says Dennis vanEngelsdorp of Penn State University. "But what we don't know is why they become susceptible to this host of pathogens, viruses and fungus."
Multiple Factors At Work
Bees have thrived for thousands of years and very likely survived many different types of diseases, so it's not clear why they seem so vulnerable now.
VanEngelsdorp says the growing consensus is that there are multiple causes working together to weaken the immune system of bees.
Environmental factors may play a role, and some scientists point to bees' nutrition. Since they're often forced to pollinate one specific crop, they may not get all the nutrients they need to be healthy. Others, like Jennifer Sass of the Natural Resources Defense Council, point to chemical exposures.
"Many pesticides and fungicides are highly toxic to bees," she says.
And scientists say it's likely that a combination of pathogens and environmental stressors work together to create a perfect storm.
ROBERT SIEGEL, host:
There's a lot of buzz among scientists about a new study linking the collapse of honeybee colonies to a fungus and to an insect virus. The findings offer a new lead in the mysterious disappearance of millions of bees.
NPR's Allison Aubrey reports.
ALLISON AUBREY: One morning back in the fall of 2004, a commercial beekeeper in Pennsylvania named Dave Hackenberg(ph) went to check on one of his hives. He was concerned because he'd noticed that his bees were dwindling in number. At 7 a.m. that day, he estimates there were about 5,000 in the hive.
Mr. DAVE HACKENBERG (Beekeeper): And by 2 o'clock in the afternoon, there was nobody home. I mean, it just they just totally disappeared.
AUBREY: The rapid disappearance of bees, vanishing in just a few days or weeks, is a signature of the phenomenon that scientists have dubbed Colony Collapse Disorder. It's linked to the loss of 40 to 60 percent of beehives over the last six years.
And if you ask Dave Hackenberg what's causing it?
Mr. HACKENBERG: Something has messed up the immune system, and the bees can't take it.
AUBREY: Lots of scientists have the same theory, but figuring out exactly why so many bees are dying is proving to be very complicated.
There have been a couple of studies pointing to different viruses and pathogens as possible causes. The latest research has found that a particular insect virus, first seen in Asian honeybees, is working in tandem with a fungus.
I reached the paper's author, Robert Kramer(ph) of Montana State, on his cell phone this afternoon.
Mr. ROBERT KRAMER (Montana State University): The interesting finding that's of significance for us it that it was the occurrence of both the virus and the fungus at the same time that seemed to correlate with the collapsing hives. So our data suggests that these two pathogens interacting together might be playing a pretty big role.
AUBREY: Kramer's excited by his findings. They offer up what he thinks is an important clue. But he says he'd be the last to say that this cracks the case or solves the mystery of vanishing honeybees.
Researcher Dennis vanEngelsdorp of Penn State says the viral sicknesses may be just one of the threats the bees face.
Mr. DENNIS VAN ENGELSDORP (Researcher, Pennsylvania State University): Well, I think that the data so far from a lot of studies, including this current one, shows that these bees get very, very sick. What we don't know is why they become susceptible to this host of pathogens, viruses and fungus.
AUBREY: As a species, bees have thrived for thousands of years and likely survived many different types of diseases. So why now have bees become so vulnerable? vanEngelsdorp says the growing consensus is that there are multiple causes working together to weaken the immune system of bees.
It may be a combination of environmental factors, as researcher Leonard Foster, of the University of British Columbia. One possibility?
Dr. LEONARD FOSTER (Researcher, University of British Columbia): Exposure to chemicals in the environment that bees are picking up when they pollinate flowers.
AUBREY: Or when they pollinate crops for farmers. Scientists say it's likely that pathogens and environmental stressors combine together to create a perfect storm.
Allison Aubrey, NPR News.
SIEGEL: And if you're curious about the healing powers of honey for people, you can check out Allison's video at npr.org. Transcript provided by NPR, Copyright NPR.