All About Nosema – pg3

From: Page 35 Bee Craft Digital September 2011

Bee-Craft-Sept-11-pg35several forms but is most familiar as a round cyst. It passes round the colony in the same way as nosema. Not much is known about amoeba, but it is rare, has no outward symptoms and probably has little effect so, in practice, can currently be ignored. An affected colony can be transferred onto clean comb if necessary. Like nosema, it can only be identified by microscopic examination.


The presence of nosema (but not which type it is) can be confirmed using a microscope with X400 magnification. It is a very simple technique if you have the right microscope. About 30 bees are collected and their abdomens mashed up in a pestle and mortar with a few drops of water. A single drop of the resulting ‘soup’ is put onto a microscope slide and covered with a coverslip. Under the microscope, look for little rice-shaped grains. Your local association may well have a microscopist who can do this examination for you as it is otherwise quite an expensive test. Although the spores of N apis and N ceranae have slight morphological differences, there is not much discernable difference under a light microscope and the only reliable way to distinguish them is under an electron microscope or using the fancily named Polymerase Chain Reaction (PCR) analysis – neither of which is available to the average beekeeper.


The antibiotic fumagillin is available as Fumidil® B and is usually added to the autumn feed. This will kill the active stage of nosema in the adult bee and will successfully reduce the parasite burden, at least temporarily. There is no point in using it if nosema is not present so the colony should be tested first to determine if it is needed.

Treatment Regimes

As an autumn feed: Each colony should receive 166 mg of fumagillin in the autumn feed. A small pack of Fumidil® B represents 0.5 gm of fumagillin (25 gm of soluble powder) and will treat three colonies.

  • 1 Heat seven pints of water per colony to 38° C (do not exceed 49° C or the active ingredient will be damaged).
  • 2 Add one-third of the small pack for each colony and dissolve.
  • 3 While water is still hot add 6.35 kg (14 lb) of sugar per colony and stir to make clear syrup.
  • 4 Feed the syrup to the bees in the usual way. As a spring treatment for small colonies:
  • 1 Dissolve a small (25 g) pack of Fumidil® B in 12 litres of strong sugar syrup and syringe 50 ml to 100 ml of warm syrup over the top bars and bee ways near the cluster to encourage the bees to clear it up.
  • 2 Repeat three to five times at two-day intervals then feed remaining syrup in a contact feeder.
  • 3 A feed supplement such as Vitafeed® Gold used in a similar manner may be beneficial (follow the instructions on the pack).

Caution – Use protective equipment when handling Fumidil® B. Prepared Fumidil® B in syrup is viable for only two weeks.

Source: NBU (CSL/National Bee Unit) Fact Sheet no 15 by John Verran.

If you have a deeply rooted objection to feeding antibiotics, you can gain some temporary respite by uniting ‘sick’ colonies to form a large enough unit to survive in the short term. However, this enlarged colony will need shaking onto clean combs (and some luck) if it is to survive in the long term.


Spores of both nosema species can remain viable on the combs (whether in or out of the hive) for a year or more and the disease is easily spread through the use of contaminated combs. To clear persistent spores from an infected colony, brood combs need to be replaced. There are several ways to do this which have varying efficiency. The standard advice is to replace two or three combs each year with clean (fumigated) comb or foundation. Comb replacement doesn’t act as a treatment but will help to reduce spore numbers. However, for colonies infected with nosema you will need to prevent the disease coming back the following year. To be properly effective this will require replacing all the combs in one go using either a shook swarm or a Bailey frame change.

Shook swarms in particular have been shown to give colonies new vigour, probably because all the horrid pathogens in the comb are completely removed.
Where combs are to be reused they should be fumigated first. Stored supers and brood frames can be fumigated

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