Are you sure that the vet diagnosed it as feline leukemia?  To the absolute
best of my knowledge, and I'm not a vet, ferrets *do not and can not get*
feline leukemia.  I even tried to look it up in Hillyer's "Ferrets Rabbits
and Rodents, Clinical medicine and surgery" and it's not listed there,
period.  Cavian (Guinea Pigs) Leukemia, yes.  Feline leukemia in ferrets, no.
 
If I were the owner, and if the vet put down four of my ferrets for "feline
leukemia" I'd be finding another vet and reporting the "former" vet to the
local board.
 
Dick B.
[Posted in FML issue 2296]