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Nosema and dysentery are not the same

Yesterday I read the following statement on the blog of a well-known beekeeper. “First I looked at the hive entrances which had signs of nosema the last time I visited. The hive looked just the same – no new nosema on the side of the hive.”

Whoa! There are at least two things wrong with this statement. First off, you cannot see Nosema on the side of a hive. What you can see on the side of a hive is bee feces, which may or may not contain Nosema. More often than not, an accumulation of runny brown feces at the entrance to a hive in spring is honey bee dysentery. Unlike human dysentery, honey bee dysentery is not caused by a pathogen but by poor diet.

It is true that Nosema apis also causes diarrhea-like feces to be deposited in or on the hive, but it cannot be distinguished from dysentery without a laboratory analysis—or at least a microscope and some training.

Secondly, Nosema ceranae, which also can infect honey bees, does not cause the bees to defecate in or on the hive. Most often bees become infected with Nosema ceranae in the summer and die in the field while out foraging. In any case, bees infected with Nosema ceranae do not leave diarrhea-like feces as a clue.

In summary, seeing no feces does not mean the bees are free of Nosema anymore than seeing feces means they are.




I wonder if Fumagilin has any affect on Nosema ceranae? I haven’t found anything with a solid, conclusive, yes or no, yet. Some say yes. Some say no. Some say a little and I still don’t know. Are there any scientific papers on this? I can’t seem to find them if there are.
They say the bees will overcome Nosema A, if you let them deal with it. They need to have it, to beat it, without treatment. They can’t beat Nosema C, from what I understand. If Fumagilin treats Nosema C, even a little, then treating is a must.
I guess I’m just not that daring yet. If I caught a serious bug, that could kill me, I would drink my Fumagilin.


The things I’ve read about Nosema are just as you say. The bees can beat N. apis but not N. ceranae by themselves. Some say Fumagilin-B works for N. ceranae and some say it works partially or not at all. Some say it requires larger doses, but no one has said (as far as I know) what those larger doses are. I don’t know anymore about this than you do.

Darwin Deming

Does regular bee dysentery in the spring need to be treated or will the bees overcome it on their own as temperatures warm and they are able to spend more time out of the hive? I do try to clean up what I can to get the feces out of the hive.



Yes, usually honey bee dysentery clears up by itself once the bees start flying and have a spring diet. I do the same thing—clean up the best I can and call it good.

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