There are many possible causes from parasites to ECE, to coccidea, to
stress, to infection, to complications of blockages, to gastroenteritis,
to...
 
You'll want to do some digging in these sites using their search features
of indices to start with:
 
1. http://www.afip.org/ferrets/index.html
 
2. http://www.miamiferret.org/fhc.
 
3. http://groups.yahoo.com/group/Ferret-Health-list
 
3. http://www.trifl.org/medical.html
 
5. http://www.ferretcentral.org
 
These are GREAT sites for MANY types of illnesses and more, and contain
useful links as well.
[Posted in FML issue 3465]