In Digest 38 see Coccidia and misdiagnosis:
 
While the majority of the outbreaks that we see are due to someone cleaning
all the cages at once, using the same bucket of soapy water and a rag to go
from cage to cage, occasionally we see outbreaks in which good husbandry is
practice.  Coccidial oocysts (the egg form) are resistant to drying, and
can live for days in a tiny bit of poop that even the pickiest person might
miss.  They do require ingestion for passage though.
 
Now, there is another possibility, which we should talk about.
Occasionally, coccidia is misdiagnosed by the vet (a hush falls over the
crowd.) Yes there are other things that hand around in poop that can be
mistaken for coccidia.  The #1 thing is yeast.  Yeasts are generally
significantly smaller, but I have seen them be misdiagnosed as coccidia,
or even worse Toxoplasma (they are very close to Toxo in size - did you
know that Toxo is also another form of coccidia)?  But occasionally, it
does happen.  This would explain why a diagnosis of coccidia is given,
but no clinical signs are seen.
 
Several years ago, in a vet journal, I saw a statement that cat or dog
coccidia could be seen in ferret feces.  I have no doubt that they can, but
they would not account for any outbreak, as cat and dog coccidia are not
infectious to ferrets, or vice versa.  While they could conceivably be
ingested, and pass on through, I believe that the chance of this happening
(and you picking up on it) is fairly astronomical.
 
Generally if diarrhea is seen, and coccidia is identified on a fecal
exam, you can pretty much guarantee that the two are related.
 
With kindest regards,
Bruce H. Williams, DVM, DACVP
 
Join the Ferret Health List at
http://groups.yahoo.com/group/Ferret-Health-list
[Posted in FML issue 3350]