We use a 1/2 dose of Vanguard DHPi for vaccinating ferrets.  I think (but
I haven't the ref book here to check) that Vanguard is the only one that
does not explicitly state in the data sheet that it is *not* safe for use
in ferrets - i.e. all the others definitely do state they should not be
used.  I have used it in a number of ferrets without problems.  However,
I don't know if it is protective for distemper, as we have almost no
distemper in dogs in this area anyway.  We checked with whoever makes
Vanguard (I know I should know, but I have children buzzing round and
can't think) and I think they said it was ok but had no data.
 
I hope this is of some help.
 
Alison the vet in England, 3 ferrets.
[Posted in FML issue 3608]