Please be advised, I am not a vet, nor do I play one on TV.
 
It's my understanding that "greenies" can be caused by any intestinal upset
or irritation.
 
Stress caused intestinal irritation CAN be life-threatening if is
accompanied by the refusal to eat.  Ulcers may develope and if left
untreated, they may begin to bleed.  This will show itself in the "greenies"
turning to black, tarry stools.
 
Aside from stress poops, I have only had personal experiance with one
illness which caused "greenies".  If I had followed "general opinion" that
it was ECE my ferret would have died.  After 1 1/2 months of testing,
treatment, and intensive care he was diagnosed with Eociniphilic Gastro
Enteritis and proper treatment was begun.  It's my understanding that this
illness is uncommon in ferrets.  Other possibilities which were considered
and ruled out were; ECE, Helicobacter, Coccidiosis, and Proliferitive Bowel.
All these will include "greenies" in the list of symptoms.
 
In conclusion, and in my opinion; "Greenies" are just a signal that there is
something wrong.  It's up to you and your vet to find what that "something"
might be.
 
SP
[Posted in FML issue 2333]