Sunday, November 14, 2010

Investigating Nosema Disease

Nosema disease is receiving considerable attention, because it is now being seen as possibly associated with honey bee Colony Collapse Disorder. As researchers began their study of all known honey bee pathogens in their search for possible causes of the large-scale die-off of honey bee colonies that started in 2006, they discovered that a new strain of Nosema disease was present In the United States. The new strain, known as Nosema ceranae, is thought to have originated with the Asian honey bee. Our honey bees, of European origin, have carried another strain of this bee disease, Nosema apis. This microorganism, which has been reclassified several times and is very similar to a fungus, causes dysentery in honey bees. Now, surprisingly, the original strain has been largely replaced by the new strain. Nosema apis has easily identified symptoms, mainly waste streaking on the hive; Nosema ceranae shows no symptoms. Nosema apis is normally a winter time disease; Nosema ceranae affects bees throughout the year. While Nosema apis was rarely considered a serious condition, Nosema ceranae seems to be much more lethal. Honey bees affected by Nosema ceranae have a shortened lifespan. For honey producers, this results in a lesser number of foragers and reduced honey harvests. The new strain is being reported to exist along with certain viruses in collapsing honey bee colonies. Both strains can be controlled by Fumagillin, our only available treatment.

Researchers at The University of Tennessee are among those studying Nosema disease. At the recent Tennessee Beekeepers Association’s annual conference, Dr. John Skinner and entomology graduate students Michael Wilson and Paul Rhoades demonstrated how to remove the honey bee mid-gut and examine the contents for Nosema spores. Like American foulbrood and chalkbrood, Nosema is a spore-forming pathogen. Nosema exists in both vegetative and spore-producing states. Microscopic analysis of infected honey bees often reveals millions of reproductive Nosema spores. In the photo Paul removes the mid-gut of a honey bee. Beekeeper Shirley Murphy observes in the background.

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