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Nature of the disease
Nosemosis is a parasitic disease of bees caused by a protozoan called Nosema apis which invades and destroys cells in the bees gut.
OIE List B Disease
Susceptible species
Apis melifera and other Apis spp.
Nosema is the most widespread adult bee disease in the beekeeping world and is found in the Pacific.
Clinical signs
The parasite invades the posterior region of the ventriculus.

Affected bees will present:

  • Unconnected wings
  • Missing hair
  • Mortality
  • Dysentery marked by brown faecal marks in the comb
Post-mortem findings
The size of the affected gut is two times the size of normal gut and the color is white instead of being light pinkish and the ventricule is white instead of being brown.
Differential diagnosis
Specimens required for diagnosis
A sample of 30 to 60 bees should be submitted for identification of the disease by microscopy observation.
Bees get infected by eating contaminated water or honey. The spore of the parasite can persist 2 years in faecal droppings and one year in honey and bee carcasses
Risk of introduction
The disease is present in most countries, however it is interesting to preserve free hives.

Drifting bees between hives and swarms from infested colonies are ways that the parasite can be spread within and between apiaries. Material and honey should also be considered at risk.

Control / vaccines
Treatment involves fumagillin fed in sugar sirop or fumigation under supervision by a technician.

To disinfect material acid acetic or heating at 60 °C for 15 minutes are efficay.

  • Office International des Epizooties, 2002
  • ROOT AI (1990), Nosema In ABC and XYZ of Bee Culture, ed Root Company, p 129-132