Good gracious!  Poor fuzzy... A couple of things come to mind.  The
swollen feet look very much like cutaneous lymphoma.  I guess a biopsy
would be the only way to diagnose that.  I've never dealt with that
personally and have only seen pics from one or two cases; they have
distinctive "puffy" and swollen look.  I've never seen it cause what
looks like open sores, though, although if left alone long enough, who
knows what it may do.
 
The mite that causes sarcoptic mange can give ferrets what is called
"foot rot."  I know the toenails can slough off with that, but I don't
think it would lead to the sores higher up, although I could be wrong.
That problem is seem more outside the US, where ferrets are kept outdoors
more often.  It's treated with ivermectin.
 
Only other thought is some kind of horrible urine/fecal scald with
secondary infection from neglect... Or a burn of some sort...
 
She could probably use some pain meds, if they're not being given yet.
 
I have dealt with a ferret with a single "rotting" foot, but I believe
it was from trauma (probably something wrapped around her leg for a long
period of time, cutting off the blood supply).  It was only one foot.
In her case, amputation was completely unavoidable, and she gets around
fine.  So, of this ferret is able to be healed because her problem isn't
terminal, but the one foot needs to be amputated, it really can work
out fine.  I have some pics of her foot and the days leading up to the
surgery here:
 
http://www.unc.edu/~pjdutche/nana/
 
Good luck to this poor fuzzy.  Sad to say, if she can't be diagnosed and
is not responding to any therapy, it may be best to gently hold her and
let her go.  That looks terribly painful.
 
Best wishes,
-Pam S.
[Posted in FML issue 3820]