Scientists link fungus to mysterious Honeybee deaths
by Shubha Krishnappa - April 27, 2007 - 0 comments
Scientists from University of California, San Francisco announced Wednesday that they have identified a parasitic fungus and a virus as two potential causes of the widespread death of honeybee colonies in the US and Europe.
Mysterious honeybee deaths, a phenomenon called Colony Collapse Disorder, or CCD, were previously linked to cell phone towers and radio waves by some scientists, but researchers in California yesterday said that a fungus that caused widespread loss of honeybee colonies in Europe and Asia is playing the crucial role in the sudden deaths of the buzzing insects in the United States.
Tests of genetic material taken from a "collapsed colony" in Northern California's Merced County found genes of the single-celled parasite called Nosema ceranae, a once-rare microbe that previously affected only Asian bees but might have evolved into a strain deadly to those in Europe and the United States, said Joe DeRisi, a biochemist at the University of California, San Francisco.
To perform the tests, DeRisi, who also found the SARS virus in 2003, used a technique known as "shotgun sequencing," that allows rapid reading of a genetic code and then compares it with computerized libraries of known genes from thousands of germs. It is the same approach that has been used to read the genomes, or the genetic code, of creatures ranging from bacteria to human beings.
Although the new findings represent the first solid evidence pointing to a potential cause of the disorder, but DeRisi says the results are "highly preliminary" and based on only a few hives. "We don't want to give anybody the impression that this thing has been solved."
However, some other researchers from around the country said Wednesday that Nosema ceranae has shown up in their hives as well. Researchers have also found two other fungi and a number of viruses in the dead bees from collapsed hives.
Nosema ceranae is "one of many pathogens" in the bees, according to entomologist Diana Cox-Foster of Pennsylvania State University, who was one of the organizers of a meeting in Washington this week at which about 60 bee researchers discussed Colony Collapse Disorder.
"By itself, it is probably not the culprit ... but it may be one of the key players," Cox-Foster said. "We still haven't ruled out other factors, such as pesticides or inadequate food resources following a drought," she added.
The mysterious phenomenon was first noticed last year in October in the United States when beekeepers started releasing their insects near crops to pollinate plants. It spread rapidly, with beekeepers reporting heavy losses of between 30% and 90% of buzzing insects. Some 24 American states have now reported cases of colony collapse disorder. Then speculation arose that the honey bees had been lost to global warming or insecticide poisoning.
As per the estimates of the Apiary Inspectors of America, a national group that tracks beekeeping, more than a quarter of the country's 2.4 million bee colonies have been lost since fall.
Contrary to speculation, scientists latest hypothesis is that the bees may have been affected by a fungus. However, DeRisi agrees that more tests are needed to prove or disprove the parasite's role.
"In our results, the control bees did not have it, and the sick ones were loaded with the stuff," he said. "It is going to take a lot of time to figure out."
Honeybee or Apis mellifera is the most important pollinator for agricultural purposes. A colony of honeybees consists of a queen, several thousand workers, and, in certain seasons, a few hundred drones. A queen can lay as many as 2,000 eggs in a single day. In her four to five years of life she produces about two million eggs. More than 80,000 bees can live in a single colony.
