These may prove useful for learning more:
 
http://www.afip.org/ferrets/SCC/SCC.html
 
http://fhl.sonic-weasel.org/browse.php?msg=YG3571
 
http://fhl.sonic-weasel.org/browse.php?msg=SG276
 
Unless things have changed it looks like excision is the only real
option.
 
Unless things have changed radically (and I don't think that they have
though I know that one manufacturer was said by a third party to
considering some tests) it is NOT known how long past one year that
distemper vax of any currently used type remain effective for ferrets.
(This can NOT be accurately or safely generalized from other species
since ferrets have already turned out to differ in this regard in
relation to other vax.) I do know that at least one of the vax is not
effective for that long because of a failure to provide sufficient
protection which occurred around here in one household.
[Posted in FML issue 5016]