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''Nosema apis'' is a microsporidian, a small, unicellular parasite recently reclassified as a fungus that mainly affects honey bees. It causes nosemosis, also called nosema, which is the most common and widespread of adult honey bee diseases.〔Johannes Eckert, Karl Theodor Friedhoff, Horst Zahner, Peter Deplazes: ''Lehrbuch der Parasitologie für die Tiermedizin (German).'' 2nd Ed., Georg Thieme 2008, ISBN 978-3-8304-1072-0, p. 140.〕 The dormant stage of ''N. apis'' is a long-lived spore which is resistant to temperature extremes and dehydration, and cannot be killed by freezing the contaminated comb. Nosemosis is a listed disease with the Office International des Epizooties (OIE). ==Pathogen== thumb ''Nosema apis'' is a single-celled parasite of the western honey bee (''Apis mellifera''). The species is of the class Microsporidia, which were previously thought to be protozoans, but are now classified as fungi or fungi-related.〔Liu YJ, Hodson MC, Hall BD. (''Loss of the flagellum happened only once in the fungal lineage: phylogenetic structure of kingdom Fungi inferred from RNA polymerase II subunit genes.'' ) BMC Evol Biol. 2006 Sep 29;6:74.〕 ''N. apis'' has a resistant spore that withstands temperature extremes and dehydration. In 1996, a similar microsporidian parasite of the eastern honey bee (''Apis cerana'') was discovered in Asia, which was named ''Nosema ceranae''. Little is known about the symptoms and the course of the disease. Chinese researchers found ''Nosema ceranae'' in spring 2005 in Taiwan for the first time, and it has now been seen on western honey bees. The new pathogen was discovered in 2005 in Spain〔Higes et al.〕 and was observed to have a notably higher virulence than the western version. The disease caused by ''N. ceranae'' in western honey bees in Spain is related to heavier disease patterns deviating from the previously typical findings (unusually heavy intestine injuries in the bees, no diarrhea, preferential affliction of older collecting bees). Bees die far away from the dwellings, as when they leave they are too weak to return. This leads to collapse of the bee colony. Within a few years, a strongly increased propagation of ''Nosema'' was observed, and its occurrence was happening all year round due to the higher resistance of ''N. ceranae''. A higher reinfection rate of the bee colonies is assumed, since the pathogen survives longer in the external environment. The two pathogen types cannot be differentiated with usual routine investigations, but can be distinguished only with the assistance of molecular-genetic methods such as polymerase chain reaction. Spanish researchers regard with alarm the insurgence of ''N. ceranae'' in Spain, which has now replaced ''N. apis''. Because of this newly emergent parasite, the pathogen is assumed to be related to the substantial bee mortality observed in Spain since autumn 2004. They conjectured a similar cause of increased bee colony losses reported in other European countries, such as those experienced in France since end of the 1990s and in Germany in 2002 and 2003. In the samples of examined in German laboratories in the winter of 2005/2006, the new pathogen was present in eight of 10 examined bee hives examined (CVUA Freiburg), with the distribution varying from state to state. The bees with the classical pathogen ''N. apis'' came from Thuringia and Bavaria, whereas ''N. ceranae'' prevailed in Baden-Wuerttemberg, Bavaria, and North Rhine-Westphalia. Cases were also reported from Switzerland (July 2006) and from several regions of Italy (September 2006) where ''N. ceranae'' was found in bee colonies with increased mortality. German scientists〔Ritter, Wolfgang, (CVUA Freiburg): (Nosema ceranae. Asiatischer Nosema-Erreger festgestellt. Neu verbreitet oder erst jetzt entdeckt ) (translation: Asian nosema pathogene diagnosed. Newly distributed or only lately discovered)?] ADIZ, die Biene, der Imkerfreund (Zeitschrift der Landesverbände) 3/2006, S. 7 (Online auf der Website des Landesverbandes Schleswig-Holsteinischer und Hamburger Imker e. V.).〕 do not know whether ''N. ceranae'' was already present in Europe and simply had not yet been differentiated from ''N. apis''. The current disease processes possibly are more extreme when a ''Nosema'' affliction occurs because the colonies are already weakened by the ''Varroa'' mite or other factors that make them more susceptible. However, signs indicate the disease process of ''Nosema'' has changed, and the disease arises now all year round. The investigation of 131 bee colonies from Bavaria 〔Zohni, Dalia: ''(Zur Epidemiologie arthropodenübertragener Virosen der Honigbiene, Apis mellifera, in Bayern ) (translation: About epidemiology arthropode-transmissioned viral diseases of the honey bee, Apis mellifera in Bavaria). München, Germany 2006 (Inaugural-Dissertation at the Tierärztlichen Fakultät of the Ludwig Maximilians University of Munich).〕 supports the thesis of a causal participation between bee viruses, which were transferred by arthropods (for instance the varroa mite), and the periodically arising mass losses of life in the hives. Since only comparatively few of these colonies were afflicted with microsporidians (evidence showed 14.5% of the cases were afflicted with microsporidian spores, with half of the cases by ''N. apis'' and/or ''N. ceranae''), a correlation between microsporidian affliction and virus infection could not be determined. The question of whether the colonies were dying rather from the "new" version of ''Nosema'', which (possibly) possesses a higher pathogenicity, or due to virus diseases connected with varroa affliction, is controversially continuing to be discussed internationally among scientists and beekeepers. 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 apis」の詳細全文を読む スポンサード リンク
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