Nosema is a very destructive disease of all adult bees. Badly affected workers are unable to fly and their life span is shortened. There is a deterioration of the hypopharyngeal glands resulting in reduction of colony strength.
In winter or other weather conditions that prevent flying for prolonged periods, the infection accelerates quickly. It can easily affect the whole apiary spreading from hive to hive. It is caused by a protozoan species and its spores infect bees through ingestion, growing in the midgut. The cells increase and are ejected in the faeces.
How do I Spot it?
There is no easy way to identify and infestation of Nosema without physiological examination. However, in severe cases of infection, the abdomens of affected bees may appear to be distended and healthy bees may be separated from those showing signs of illness. On dissection, uninfected bees show individual circular constrictions in their alimentary canals which, cannot be seen easily in infected individuals. The best method of detecting Nosema involves using a microscope for bacteriological examination of the bodies of workers or queen faeces. Placed alone in a Petri dish, the queen will defecate in about an hour, the faeces appearing as colourless drops of clear liquid. This liquid can be examined under the microscope for the presence of spores, without further preparation.
Stress plays an important role in the spread of Nosema and keeping colonies strong to minimise stress is best.
Good ventilation, protection from cold and high humidity in hives. Any second hand equipment or equipment that that is suspected of being contaminated by Nosema spores should be fumigated and flamed.
Change brood combs every two years as spores are killed during wax processing. Feed affected colonies with fumagillin, as instructed by the manufacturer, especially at times of added hive stress. This is an antibiotic honey produced during dosing and must not be used in the human food chain.