I would use NO shampoo!  The less you wash them the better they smell...
unless you have hobs in rut, in which case no matter what you do they
smell.  Washing strips away the natural oils that they produce, and causes
the glands to go into overdrive.
 
Mine get washed between zero and four times a year, never more.  Usually
I wash once or twice just to rinse away skin flakes and built up grime.
Otherwise, keep their bedding changed and laundered at least weekly, and
they'll keep themselves clean!
 
As far as the lice go, I might be very wrong, but I think that headlice are
indigenous to humans.  If I am wrong, someone please let me know, that is
an interesting question.
 
The scratching ferret...yes, they do seem to love to itch.  My guess is
that with the winter came the dry air, and that is likely the cause.  If
they are scratching near the ears, they might have mites, which need to be
treated.  They could also be going through a coat change, that will cause a
lot of extra itching.  Unless they really seem miserable, I would just ride
it out for awhile, and not do anything differently (unless it is the ears
of course).  If they are still scratching in a month or so, or other
symptoms appear, time to head to the vet for a skin scrape.
 
For the ferret who is suddenly biting, if you have ruled out all
environmental factors, I would advise a vet trip.  Your ferret mite have an
ear infection or soemthing else which is causing him pain.  I mention ears,
as often when biters come into the shelter they have ear infections (often
due to terrible mite problems) and once the infections are cleared up,
their demeanor changes to sweetheart.
 
Anne
[Posted in FML issue 2929]