Nosema ceranae
| Nosema ceranae | |
|---|---|
| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Microsporidia |
| Class: | Dihaplophasea |
| Order: | Dissociodihaplophasida |
| Family: | Nosematidae |
| Genus: | Nosema |
| Species: | N. ceranae |
| Binomial name | |
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Nosema ceranae (Fries et al., 1996) |
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Nosema ceranae is a microsporidian, a small, unicellular parasite that mainly affects Apis cerana, the Asiatic honey bee. It may cause nosemosis, also called nosema (see Nosema apis, the most widespread of the adult honey bee diseases). The dormant stage of nosema is a long-lived spore which is resistant to temperature extremes and dehydration.
Nosema ceranae was first described in 1996 and was identified as a disease of Apis mellifera in 2004 in Taiwan. Since its emergence in honeybees, N. ceranae has now been identified in bumblebee species in South America, China, and England where infection studies indicate N. ceranae has a higher virulence in bumblebees than honeybees.
Researchers in Spain have analysed samples of Apis mellifera, the European honey bee, mostly sent from colonies suffering unexpected decreases in bee population per hive or lower honey production, as reported by the beekeepers during the last two to three years. In 2004, 90% of some 3,000 samples had positive results for N. ceranae. In 2005, of 800 samples, 97% had positive results. During 2006, both France and Germany have detected the disease and recognized the genetic sequence of N. ceranae in their respective territories. In the United States, N. ceranae has been detected in honey bees from Nebraska, Wisconsin, Arkansas, New York, and South Dakota using PCR of the 16S gene. In New York, N. ceranae was detected in 49 counties, and of the 1200 honey bee samples collected, 528 (44%) were positive for Nosema, from which, PCR analysis of 371 spore positive samples revealed that 96% were N. ceranae, 3% had both N. ceranae and N. apis, and 1% had N. apis only.
This pathogen has been tentatively linked to colony collapse disorder, a phenomenon reported primarily from the United States, since fall of 2006. Highly preliminary evidence of N. ceranae was reported in a few hives in the Central Valley area of California. "Tests of genetic material taken from a "collapsed colony" in Merced County point to a once-rare microbe that previously affected only Asian bees but might have evolved into a strain lethal to those in Europe and the United States." The researcher did not, however, believe this was conclusive evidence of a link to CCD; "We don't want to give anybody the impression that this thing has been solved." A USDA bee scientist has similarly stated, "while the parasite nosema ceranae may be a factor, it cannot be the sole cause. The fungus has been seen before, sometimes in colonies that were healthy." Likewise, a Washington State beekeeper familiar with N. ceranae in his own hives discounts it as being the cause of CCD. In early 2009, Higes et al. reported an association between CCD and N. ceranae was established free of confounding factors, and that weakened colonies treated with fumagillin recovered.
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