I am definitely no vet, but It sounds like your ferret has an infection
that at least partially fungal.  My dad, after serving in Guam in WWII,
came home with 'Jungle Rot' on his feet, ad faced amputation.  The
description of his syptoms sounds identical you your fert.  Qhile he was
wating for a bed at the vetrans hospital, we had run out of the meds his
doc had given.  We had some medication for our dog for a skin infection,
and out of desperation tried some on a small patch of his skin.  By that
night that patch of skin looked heather.  He treated both his feet and
was walking a week later.  He had to use it on and off for years, but he
was eventually completely healed by it.
 
This is the stuff that worked on him.  It is both an antibiotic and
antifungal.  (the description was lifted from a pharamacy site off the
internet...
 
PanalogT: A topical ointment with antifungal, antibacterial, antipruritic
(anti-itch), and anti-inflammatory properties used for a variety of skin
conditions.  It is not recommended for deep wounds or if pus is present.
Rare superficial reactions have occurred causing redness and swelling.
Oral ingestion can cause increased thirst, urination, and hunger.  Also
found under a variety of other trade names.
 
Good luck
 
Joe
Bandit (dalmation), tubby(cinnimon fert) and boots(the cat) the ancient
one aka - 'Yoda'
[Posted in FML issue 3820]