Parasitic fly could explain bee die-off

  • Updated: January 7, 2012 - 4:07 PM
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In this photo provided by San Francisco State University, an Apocephalus borealis fly implants its eggs into the abdomen of a honey bee. The A. borealis fly is suspected of contributing to the decrease in the honey bee population. Researchers say the fly deposits its eggs in the abdomen of honey bees and as the larvae grow within the body of the bee, the bee begins to lose control of its ability to think and walk, flying blindly toward light. It eventually dies and the fly larvae emerge.

Photo: Christopher Quock, Associated Press

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Northern California scientists say they have found a possible explanation for a honey bee die-off that has decimated hives around the world: A parasitic fly that hijacks the bees' bodies and causes them to abandon hives.

Scientists say the fly deposits its eggs into the bee's abdomen, causing the infected bee to exhibit zombie-like behavior by walking around in circles. The bee leaves the hive at night and dies. The symptoms mirror colony collapse disorder, in which all the adult honey bees in a colony suddenly disappear.

The disease is of great concern, because bees pollinate about a third of the U.S. food supply. Its presence is especially alarming in California, the nation's top producer of fruits and vegetables, where bees play an essential role in the $2 billion almond industry and other crops.

The latest study, published in the science journal PLoS ONE, points to the parasitic fly as the new threat to honey bees. It's another step in ongoing research to find the cause of the disease.

Researchers haven't been able to pin down an exact cause of colony collapse or find a way to prevent it. Research so far points to a combination of factors including pesticide contamination, a lack of blooms -- and hence nutrition -- and mites, fungi, viruses and parasites. Interaction among the parasite and multiple pathogens could be one possible factor in colony collapse, according to the latest study by researchers at San Francisco State University. It says the phorid fly, or apocephalus borealis, was found in bees from three-quarters of the 31 hives surveyed in the San Francisco Bay area.

The combination of a parasite, pathogens and other stressors could cause die-off, lead investigator John Hafernik said. The parasitic fly serves as a reservoir that harbors pathogens -- honey bees from parasite-infected hives tested positive for deformed wing virus and other pathogens, the study found.

"We don't fully understand the web of interactions," Hafernik said. "The parasite could be another stressor, enough to push the bee over tipping point. Or it could play a primary role in causing the disease."

PROGRESS REPORTED IN CREATING AIDS VACCINE

An experimental vaccine protects some monkeys against getting infected with that species' version of the virus that causes AIDS and appears to make the disease more manageable in those that aren't protected, researchers reported in the journal Nature. It is further evidence that after decades of disappointment, scientists are making slow progress toward an AIDS vaccine.

"We think this is both a theoretical advance as well as a practical one," said Dan Barouch of Harvard Medical School, who led the research.

"As far as animal trials go, this is a solid step," said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, which provided some funding.

Collaborators at 10 institutions tried out four real vaccines and one sham on rhesus monkeys. The vaccines used modified cold or herpes viruses to either carry the immunogens or boost the immune response, and sometimes for both purposes. The best-performing vaccine, which used two different strains of adenovirus that normally causes colds, reduced an animal's chance of becoming infected by 80 percent (although with enough exposure, infection was inevitable). Also, once a vaccinated monkey became infected, it showed evidence of a more robust immune response.

OLDER BRAINS BENEFIT FROM FOUR VITAMINS

Higher blood levels of omega-3 fatty acids and vitamins B, C, D and E are associated with better mental functioning in the elderly, a study found.

Researchers measured blood levels of these nutrients in 104 men and women, whose average age was 87. The scientists also performed brain scans to determine brain volume and administered six commonly used tests of mental functioning. The study is in the Jan. 24 issue of Neurology.

Researchers found that people with the highest blood levels of the vitamins scored higher on the cognitive tests and had larger brain volume than those with the lowest levels. Omega-3 levels were linked to better cognitive functioning and to healthier blood vessels in the brain, but not to higher brain volume, which suggests that these beneficial fats may improve cognition by a different means. Higher blood levels of trans fats, on the other hand, were significantly associated with impaired mental ability and smaller brain volume.

The lead author, Gene Bowman, a neurologist at Oregon Health and Science University, said the study could not determine whether taking supplements would decrease the risk for dementia. But he added: "What's the harm in eating healthier?"

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