Nosema is a fungus that affects adult bees. With the correct treatment colonies will respond favorably. Nosema is most prevalent in colonies that are stressed, shipped in a package or confined.
The symptoms of Nosema are rather subtle.
Crawling disoriented bees
Bees abandoning the brood to cluster elsewhere
Colonies not consuming supplemental feed
Midgut is swollen and creamy white in color
Heave consentration of Bee feces at hive entrances, top bars, inner walls, and on other items in theye apiary.
Note: Dysentery can also be caused by poor quality food stores, confinement, and feed with heavy concentration of impurities in it.
How it Spreads
Robbing Bees Drifting
Infected Food Stores or pollen
Their are no registered treatments for Nosema
The most effective control of the disease relies on maintaining strong hives and taking precautions to reduce the build-up of the disease.
Maintain strong, healthy hives and make sure the appropriate nutrition is available to bees. Using young queens, removing old comb will help keep colonies strong and remove possible causes of stress, which can make the colony more susceptible to the disease.
It is also good practice to try and avoid moving hives, or inspecting hives during winter, as inspections and movements at this time can increase the stress levels within the colony. When getting hives ready for winter, always ensure that there are not excess boxes on the hive, as well as ensure that there is enough good quality honey and pollen for the colony. If there is not, consider feeding a protein rich pollen supplement and sugar feeding.
Bees can be sampled for Nosema using a microscope. scientificbeekeeping.com has a wealth of information on Nosema.