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Have you written on bee pollen being contaminated by sick bees?
 

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Have you written on bee pollen being contaminated by sick bees?


You've heard of the bees disappearing. Well, they said they found all kinds of garbage in their pollen, including insecticides, virus, bacteria and fungi. How safe is pollen?

"Much more startling was the outcome of our team's search for pesticides, for which we enlisted the help of Pennsylvania State University researchers Maryann Frazier, Jim Frazier and Chris Mullin and of Roger Simonds, a chemist at the USDA lab in Gastonia, N.C. (By coincidence, Simonds happens to be a beekeeper himself.) His broad-spectrum analysis, sensitive to insecticides, herbicides and fungicides, found more than 170 different chemicals. Most stored-pollen samples contained five or more different compounds, and some contained as many as 35. But although both the levels and the diversity of chemicals are of concern, none is likely to be the sole smoking gun behind CCD: healthy colonies sometimes have higher levels of some chemicals than colonies suffering from CCD.
 
No neonicotinoids were found in the original samples. But these or other pesticides cannot yet be exonerated. Honeybee colonies are dynamic, and our initial sampling was not we took samples only once. It remains possible, if not likely, that bees afflicted by CCD were harmed by a chemical or mixture of chemicals not evident at the time we collected samples.
 
Our attempts to identify a new infectious disease or a new strain of an old one that could be at the root of CCD initially looked as if they would go nowhere fast. None of the known bacterial, fungal or viral diseases of bees could account for the CCD losses, so we had no clue what to look for.
 
Then Cox-Foster, with Ian Lipkin's group at Columbia University (and with help from biotech company 454 Life Sciences in Branford, Conn.), turned to a sophisticated microbe-hunting method called metagenomics. In this technique, nucleic acids (DNA and RNA) are collected from an environment containing many different organisms. The genetic material is all blended together and minced into pieces short enough that their sequences of code "letters" can be deciphered. In ordinary gene sequencing, researchers would then use computer software to put the pieces back together and reconstruct the genome of the original organism. But in metagenomics, the genes belong to different organisms, and so sequencing produces a snapshot of the sequences in a collection of organisms, including microscopic ones, in an ecosystem. Metagenomics has been used to survey environments such as seawater and soil, revealing a surprising diversity of microorganisms. But it can also be applied to detecting microorganisms hosted by a larger organism, living either as collaborators (in symbiosis) or as infections.
 
Naturally, most gene sequences in our samples were from the bees themselves. But those were easy to filter out because, fortunately, the honeybee genome had just been sequenced. Nonbee sequences were then matched to genetic sequences belonging to known organisms. Researchers with expertise in molecular analysis of organisms including bacteria, fungi, parasites and viruses joined our team to identify potential culprits.
 
The CSI-style investigation greatly expanded our general knowledge of honeybees. First, it showed that all samples (CCD and healthy) had eight different bacteria that had been described in two previous studies from other parts of the world. These findings strongly suggest that those bacteria may be symbionts, perhaps serving an essential role in bee biology such as aiding in digestion. We also found two nosema species, two other fungi and several bee viruses.
 
But one bee virus stood out, as it had never been identified in the U.S.: the Israeli acute paralysis virus, or IAPV. This pathogen was first described in 2004 by Ilan Sela of the Hebrew University of Jerusalem in the course of an effort to find out why bees were dying with paralytic seizures. In our initial sampling, IAPV was found in almost all though not all colonies with CCD symptoms and in only one operation that was not suffering from CCD. But such strong correlation was not proof that IAPV caused the disease. For example, CCD could have just made the bees exceptionally vulnerable to IAPV infection.
 
Case Closed?
From subsequent work on IAPV, we know that at least three different strains of the virus exist and that two of them infect bees in the U.S. One of the strains most likely arrived in colonies flown in from Australia in 2005 after the U.S. government lifted a ban on honeybee importation that had been in effect since 1922. (The almond industry lobbied to lift the ban to prevent a critical shortage of pollinators at blossom time.) The other strain probably showed up earlier and is quite different. Where that one came from is unknown; it may have been introduced by way of importation of royal jelly (a nutrient bees secrete to feed their larvae) or a pollen supplement, or it may have hitchhiked into the country on newly introduced pests of bees. The data also suggest that IAPV has existed in bees in other parts of the world for a while, developing into many different strains and possibly changing rapidly.
 
In an effort to settle the issue of IAPV's role, Cox-Foster experimented with healthy honeybees that had no previous exposure to the virus. Her team placed hives filled with bees into greenhouses and fed the insects sugary water laden with IAPV. Sure enough, the infection mimicked some symptoms of CCD. Within one or two weeks of exposure, the bees began to die, twitching with paralytic seizures on the ground. The bees were not dying near the hives, just as one would expect in CCD. So those findings seemed to support the notion that IAPV can cause CCD or at least contribute to the problem.
 
 
Additional sampling efforts by several groups showed, however, that IAPV was widespread in the U.S. and that not all infected colonies had symptoms of CCD, implying either that IAPV alone cannot cause the disease or that some bees are predisposed to be IAPV-resistant. In particular, a joint study the two of us initiated in 2007 with the USDA has tracked colonies owned by three traveling beekeepers and has observed colonies that were infected with IAPV without collapsing. Some of those colonies have later been able to rid themselves of the virus.
 
The growing consensus among researchers is that multiple factors such as poor nutrition and exposure to pesticides can interact to weaken colonies and make them susceptible to a virus-mediated collapse. In the case of our experiments in greenhouses, the stress of being confined to a relatively small space could have been enough to make colonies succumb to IAPV and die with CCD-like symptoms. More recent results from long-term monitoring have identified other unexpected factors for increased colony loss, including the fungicide chlorothalonil. Research is now focused on understanding how these factors relate to colony collapse.
 
A vaccine or cure for bee viruses and IAPV specifically would be desirable. Unfortunately, vaccines will not work on honeybees, because the invertebrate immune system does not generate the kind of protection against specific agents that vaccines induce in humans and other mammals. But researchers are beginning to pursue other approaches, such as one based on the new technique of RNA interference [To see related sidebar please purchase the digital edition], which blocks a virus from reproducing inside a bee's cells. A longer-term solution will be to identify and breed virus-resistant honeybees. Such an effort could take years, though, perhaps too many to avoid having a large number of beekeepers go out of business.
 
Meanwhile many beekeepers have had some success at preventing colony loss by redoubling their efforts at improving their colonies' diets, keeping infections and parasites such as varroa and nosema in check, and practicing good hygiene. In particular, research has shown that sterilizing old beehive frames with gamma rays before reusing them cuts down the risk of colony collapse. And simple changes in agricultural practices such as breaking up monocultures with hedgerows could help restore balance in honeybees' diets, while providing nourishment to wild pollinators as well.
 
Humankind needs to act quickly to ensure that the ancient pact between flowers and pollinators stays intact, to safeguard our food supply and to protect our environment for generations to come. These efforts will ensure that bees continue to provide pollination and that our diets remain rich in the fruits and vegetables we now take for granted."
 
Editor's Note: This story was originally published with the title "Saving the Honeybee"

www.benziger.com/

 
 

 
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