Causal agent

Nosema apris and Nosema ceranae   This is a microsporidia – unicellular parasite.  The spores are large oval bodies 4-6mm long and 2-4mm wide

Age group




Adult - worker









Clinical signs


Mainly seen in the winter and spring after periods of bad weather

Mainly affects workers, but can affect drones and the queen


Results in “dysentery” where the works defecate in the hive rather than during “cleansing flights”.   The dysentery can be seen as yellow stripes on the outside of the hive or even inside the hive.

The worker may appear to have an increased girth of her abdomen.  There may be a missing sting reflux.  An affected queen might lead to supersedure of the queen.


Egg production drops as the queen’s ovaries degenerate


There can be a large number of dead bees in the apiary, but in general bees die away from the hive.

Secondary infections

Worker bees are unable to fly move by crawling with disjointed wings.


Also appears to be related to Black Queen Cell Virus


Has a role to play in Colony Collapse Disorder



The spores are extremely long lived and are not destroyed by freezing

Newly emerged bees are free from the infection



The bees become infected through faecal materials.  Generally after being confined to their hive.

Post-mortem Lesions


The healthy ventriculus is straw brown and the individual circular constrictions can be clearly seen. In infected bees the ventriculus is white, soft and swollen and the constrictions are obscured






DSC02019 DSC02019                       Nosema microscope

  1. Ventriculus swollen with loss of constrictions
  2. Ventriculus normal size with constrictions
  3. Nosema from the ventriculus x40

The digestive tract can be easily obtained from a bee.

Remove the bees head.

Grasp as much of the stinger as possible with a pair of fine tweezers and then with a steady, gentle pull withdraw the entire digestive tract.

Nosema affects pollen digestion, thus reducing the life of the bee

Under development of hyopopharyngeal glands may be seen




Place a glass-slide collect faecal material from worker bees near the hive entrance.  Scrape off the deposit, mix with water and make a wet mount.

Queen bees can be examined by placing them on a small petri dish and allow them to walk freely.  Within an hour the queen will have defecated – drops of clear, colourless liquid which can then be transferred by a capillary tube.

Microscopic examination of the ventricular contents.

Take a whole bee and macerate in water.  Examine the fluid to reveal the Nosema spores


The number of spores can be calculated using a haemocytometer.


May also recognise an Amoeba when looking for Nosema.  Amoeba Malpighamoena mellificae).  This does not appear to be significant.  However, it can result in cysts in the Malpighian tubules – revealed by gentle crushing the Malpighian tubules with a cover slip.

Other protozoa that may be recognised include flagellates of the Crithidia spp.



Fumidil B (Fumigillin)

Disinfect honeycomb and utensils

Some evidence that thymol may be effective

Be careful when manipulating the frames.  If bees are trapped and quashed, they will spread Nosema.


Heat treat for more than 50°C for 24 hours to kill spores

Ensure that the crude protein content of bees is above 40%.  When bees drop to less than 30% they become more susceptible to Nosema.

Shook swarm technique may be helpful

Ensure all bee keeping equipment is clean

Be careful of other people bee equipment

Do not reuse old combs from colonies that have died out.

Do not exchange combs between colonies

Common differentials