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 Spain.

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.^[1][2] 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.^[3]

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 Merced 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."^[4][5] 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."^[6] 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."^[7] Likewise, a Washington State beekeeper familiar with N. ceranae in his own hives discounts it as being the cause of CCD.^[8] 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.^[9]

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.^[10]

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, which is faster than bees exposed to N. apis. The foraging force seems to be affected the most. They leave the colony and are too weak to return, thus dying in the field. This leaves behind a small cluster and a weak colony, very similar to the symptoms of 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.^[11] 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.^[12][13]

References[link]

• Fries,I.M., Feng,F., da Silva,A.J., Slemenda,S.B. and Pieniazek,N.J. Nosema ceranae n. sp. (Microsporidia, Nosematidae), morphological and molecular characterization of a microsporidian parasite of the Asian honey bee Apis cerana (Hymenoptera, Apidae). Eur. J. Protistol. 32, 356-365 (1996).
• Nosema ceranae, a new microsporidian parasite in honeybees in Europe, Higes M, Martín R, Meana A., J Invertebr Pathol. 2006 Jun;92(2):93-5.
• Higes, Mariano; u. a.: El Síndrome de Despoblamiento de las Colmenas en España (The bee dying syndrome in Spain). In: Vida Apícola 133 (September/Oktober 2005), 15-21 (Montagud Editores, Barcelona, Spanien).
• Higes, Mariano; u. a.: Nosema ceranae, a new microsporidian parasite in honeybees in Europe. In: Journal of Invertebrate Pathology 91 (2006) (Elsevier).
• Huang, Wei-Fone; u. a.: Complete rRNA Sequence of the Nosema ceranae from honeybee (Apis mellifera). National Taiwan University, Taipeh 2005.
• Klee, J., Besana, A. M., Genersch, E., Gisder, S., Nanetti, A., Tam, D. Q., Chinh, T. X., Puerta, F., Ruz, J. M., Kryger, P., Message, D., Hatjina, F., Korpela, S., Fries, I. & Paxton, R. J. (2007) Widespread dispersal of the microsporidium Nosema ceranae, an emergent pathogen of the western honey bee, Apis mellifera. Journal of Invertebrate Pathology.
• Ritter, Wolfgang, (CVUA Freiburg): Nosema ceranae. Asiatischer Nosema-Erreger festgestellt. Neu verbreitet oder erst jetzt entdeckt (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.).
• Williams, G.R., Sampson, M.A., Shutler, D., Rogers, R.E.L. 2008. Does fumagillin control the recently detected invasive parasite Nosema ceranae in western honey bees (Apis mellifera)? Journal of Invertebrate Pathology 99: 342-344.
• "Colony Collapse Disorder Preliminary Report". Mid-Atlantic Apiculture Research and Extension Consortium (MAAREC) - CCD Working Group. 2006-01-05. pp. 22. http://maarec.cas.psu.edu/pressReleases/FallDwindleUpdate0107.pdf. Retrieved 2007-04-24.