Nosema - is a disease of adult bees caused by a spore-forming protozoan (Nosema apis) that invades the digestive tracts of honey bee workers, queens, and drones. The spores of the Nosema apis, usually ingested with food or water by the adult bee, germinate and multiply within the lining of the mid-gut. Millions of spores are shed into the digestive tract and are passed in the faeces. Damage to the bees digestive tract produces dysentery and weakens the bees, shortening the productive life of the worker, and reducing its ability to produce brood food. This in turn affects brood production and colony development particularly in early season. Infected queens' egg production and life span are reduced, leading to supersedure. Infected workers, unlike healthy workers, may defecate in the hive. Diseased colonies usually have increased winter losses and decreased honey production.
Nosema infections are frequently present in most apiaries at low levels without causing significant damage. It is aggravated by stress, colony disturbance in winter as well as during summer increases the risk of detectable disease level.
Note: This is a not a notifiable disease however any suspected incidence of Nosema should be remediated without delay, inform your local beekeeping association / community to alert them of its presence.
Download the Nosema Info Sheet to obtain a printable version of Nosema information, detection and treatment methods for your records.
Image Courtesy The Animal and Plant Health Agency (APHA), © Crown Copyright
Dysentery on the top bars of frames caused by Nosema apis
The presence of nosema disease is not usually recognised until most of the bees in the colony are infected since it does not produce signs or symptoms that are easily recognized under field conditions. Defecation in the hive and signs of unusual faeces on hive parts can be tell tale signs. The only positive way of identifying the disease is through dissection of adult bees. Suspect colonies should have samples taken and sent off to SASA in a paper bag for analysis.
Hive Examination - Examination of hives, components and debris is required especially in spring. Abnormalities such as the signs of dysentery, crawling and dead bees are easily spotted.
Monitoring - Vigilance is important with all honeybee diseases. Check all apiaries and colonies regularly for health and suspect any colonies that are not thriving where there is no already known reason. Colonies that die out should be examined thoroughly and sealed to prevent robbing and spread of any disease present.
Transferring the infected colony on to clean comb and disinfecting comb and hives parts is recommended. Prevention is the best method of controlling this condition by maintaining healthy, strong and vigorous colonies that display good hygienic traits. Always ensure there is enough available food for the colony during periods of bad weather. Good husbandry contributes greatly to overall colony behaviour and health, thereby avoiding the conditions in which Nosema can occur. Fumidil 'B' can be used in spring and autumn to inhibit spore reproduction in the bee gut however it does not kill the spores. Sterilisation of contaminated equipment can be carried out by the Acetic acid sterilization process. Dead brood will be removed by bees from the cells as soon as the colony grows stronger and returns to normal. Disease prevention is best practice, maintain good apiary housekeeping:
Nosema spores can exist in beekeeping equipment, honey, wax, etc. and can spread during normal hive / colony manipulations.