Allow me to restate the question.
Can anyone on the List provide a single citation, with evidence rather  a
simple repeating of a claim, that either species of nosema has been shown
to cause diarrhea?

Correlation and causality are two different things.  Diarrhea can spread
nosema spores, but that doesn't mean the nosema caused the diarrhea.  This
association appears to have been misinterpreted by many.

Here's a typical example.
"Mederle Narcisa et al (2017) related that 178 (55%) of 323 samples of bees
collected from the apiary located in Timis County were diagnosed with
nosemosis. Of the total bee samples diagnosed with nosemosis, 69% had no
disease symptoms, 18% were dead colonies, 8% were colonies depopulated, 4%
missing colonies, and 1% diarrhea colonies."
http://www.usab-tm.ro/USAMVBT_Revista_ro_1086.html

Yet despite only 1% of the nosema-infected colonies exhibiting diarrhea,
the above authors concluded "At these bee colonies, symptoms of diarrhea
have been associated with very high levels of Nosema infection."  This sort
of conclusion strains credulity.

More accurately, Maiolino stated that:
"The stereomicroscopic and microscopic observations of the sampled honey
bees did not reveal any visible sign of anatomical changes. In fact there
weren’t signs of diarrhea and the examined organs had a normal appearance."
doi: 10.7243/2054-3425-2-4

The above observation has been published a number of times by various
authors.  Yet the claim that nosema causes diarrhea is repeated again and
again.  I'd be happy to change my assessment if anyone can provide any
valid evidence showing that nosema actually CAUSES diarrhea or dysentery.

If anyone seriously wants to understand nosema, I'd refer to GF White's
treatise in USDA Bulletin 780, page 154, available from Google Books.


Randy Oliver
Grass Valley, CA
530 277 4450
ScientificBeekeeping.com

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