Nosema Disease
Krankheiten
Nosemosis is the most common disease of adult bees.
Nosemosis is the most common disease of adult bees. It is caused by the microsporidia Nosema apis and Nosema ceranae, which attack the midgut epithelium as intestinal parasites. The spores are taken up orally with food and excreted again in the feces, so the infection spreads via soiled combs, via robbing, and via beekeeping work within a colony and between colonies.
The two species present differently. Nosema apis is mainly a spring problem and is often accompanied by diarrhea: fecal spotting on combs, frames, hive, and at the entrance, weakened colonies, bee mortality, and sluggish spring development, in extreme cases so-called spring dwindling. Nosema ceranae can occur year-round and often runs its course without the typical fecal spotting, but instead with bees unable to fly, unexplained loss of bees, declining colony strength, and increased winter losses.
A reliable diagnosis is not possible in the field. It is made in the laboratory by microscopic detection of spores, which requires a sample of about a hundred bees. The two species can only be distinguished by PCR, which is usually subject to a fee. Fecal spotting alone does not prove nosemosis; it also occurs with non-infectious dysentery.
There are no approved medicines in either Germany or Austria. Only beekeeping management is effective: keeping colonies compact, providing good winter feed, promoting bee turnover through good care and pollen supply, melting down combs soiled with feces, cleaning and disinfecting hives, and requeening with a young, vigorous queen. Severely damaged colonies that can no longer develop are better dissolved.
Prevention includes a sunny, sheltered, and dry site, consistent comb hygiene, timely and sufficient feeding, and not leaving forest honey or melezitose honey in the colony as winter stores. Uniting diseased colonies with healthy ones and moving combs from colonies showing symptoms are to be avoided. There is no reporting requirement.