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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 (Huang et al., 2007; submitted in 2005 but published in 2007). Since its emergence in honeybees ''Nosema ceranae ''has now been identified in bumblebee species in South America, China, and England where infection studies indicate ''Nosema 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/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 ''Nosema 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.〔Chapon, L., M.D. Ellis, and A.L. Szalanski. 2009. ''Nosema'' and tracheal mites in the north central region – 2008 survey. Proceedings of the American Bee Research Conference. American Bee Journal 149: 585-586.〕〔(Population genetics and distribution of ''N. ceranae'' in the United States, University of Arkansas Social Insect Genetics Lab )〕 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.〔Szalanski, A.L., J. Whitaker, and P. Cappy. 2010. Molecular diagnostics of ''Nosema ceranae'' and ''N. apis'' from honey bees in New York. Proceedings of the American Bee Research Conference. American Bee Journal 150: 508〕 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 (USA). "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. News articles published in October 2010 quoted researchers who had discovered that Nosema fungus had joined with a previously unsuspected virus, Invertebrate Iridescent Virus, or IIV6, dealing test bee colonies a lethal blow. Neither the fungus nor the virus alone kill all the test group, but the two combined do. Both the fungus and the virus are found together with high frequency in hives that have suffered CCD. Final testing is in progress with field tests on colonies.〔 〕 ''N. ceranae'' and ''N. apis'' have similar life cycles, but they differ in spore morphology. Spores of ''N. ceranae'' seem to be slightly smaller under the light microscope and the number of polar filament coils is between 20 and 23, rather than the more than 30 often seen in ''N. apis''. The disease afflicts adult bees and depopulation occurs with consequent losses in honey production. One does not detect symptoms of diarrhea like in ''Nosema apis''. The most significant difference between the two types is how quickly ''N. ceranae'' can cause a colony to die. Bees can die within 8 days after exposure to ''N. ceranae'' (Higes et al. 2006), a finding not yet confirmed by other researchers. The forager caste seems the most affected, leaving the colony presumably to forage, but never returning. This results in a reduced colony consisting mostly of nurse bees with their queen; a state very similar to that seen in CCD. There is little advice on treatment but it has been suggested that the most effective control of ''Nosema ceranae'' is the antibiotic fumagillin as recommended for ''Nosema apis''.〔Higes et al. 2009. Honey bee colony collapse due to ''Nosema ceranae'' in professional apiaries. Environmental Microbiology Reports, Vol. 1, No. 2. pp. 110-113.〕 The genome of ''Nosema ceranae'' was sequenced by scientists in 2009. This should help scientists trace its migration patterns, establish how it became dominant, and help measure the spread of infection by enabling diagnostic tests and treatments to be developed.〔Cornman et al. Genomic Analyses of the Microsporidian Nosema ceranae, an Emergent Pathogen of Honey Bees. PLoS Pathogens, 2009; 5 (6): e1000466 〕 ''Nosema ceranae'' is apparently released from the suppressive effects of fumagillin at higher concentrations than that of ''Nosema apis''. At fumagillin concentrations that continue to impact honey bee physiology, ''N. ceranae'' thrives and doubles its spore production. The current application protocol for fumagillin may exacerbate N. ceranae infection rather than suppress it. Fumagillin application should be a major cause of ''N. ceranae'' dominance in this time. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nosema ceranae」の詳細全文を読む スポンサード リンク
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