An outline of noninfectious, parasitic, infectious, and cancerous
health problems in the pet ferret is also available [11.2.4], as are
brief explanations of some of the more common ones [11.1].

NOTE: I am not a veterinarian.  I haven't even owned ferrets very
long.  (Dr. Bruce Williams, on the other hand, -is- a vet and ferret
expert.)  The following is by no means a comprehensive list of
symptoms of disease in ferrets.  However, some of the more common
problems are often accompanied by these symptoms.  If you notice one
of these, or any other unusual behavior, see your vet.

ALSO: Ferrets are small.  While they generally enjoy good health, any
kind of disease or disorder can be fatal in a surprisingly short time,
so if you suspect a problem, see your vet immediately.

Lethargy, lack of playfulness, loss of appetite, dull/glassy eyes, etc.
  Symptomatic of a number of problems.

Lack of bowel movement
  If your ferret has gone longer than usual without using the litter
  pan (or some other corner) productively, he may have an intestinal
  blockage.  Certainly by the time it's been 24 hours you should go to
  the vet immediately.  Note that a ferret can continue to defecate
  for as much as a day even with a blockage, since there's still waste
  in the intestines to be eliminated.

  Dr. Bruce Williams, DVM, adds:

     More often than not, [the cause of a lack of bowel movement] is a
     lack of food intake for some other reason.

     Ferrets generally go to the litter three or four times a day.
     Owners should look for adequate stools, although some may be a
     little loose.  Also look for string-like stools.  Ferrets with
     intestinal blockages can continue to pass stool which is very
     thin- like a pencil lead.  But adequate ferret-proofing [5.1] is
     much more important than stool-watching.

Swollen or painful abdomen
  Bloating may come from many problems such as heart disease, splenic
  enlargement, or even just fat animals.  Pain could be from any of
  several disorders, but the most common is an intestinal blockage,
  caused by eating something indigestible such as a sponge or an
  eraser.  Not all blockages cause abdominal pain, though.

Change in "bathroom" habits
  Suddenly refusing to use a litter pan or missing a lot more than
  usual, signs of discomfort or distress while using a pan, or any
  funny color or texture in the feces [10.4] or urine could be a sign
  of any of a number of problems.  Stress, perhaps from a change in
  environment, can also cause this.

Lumps on the body or feet
  These may be cysts or infections, or they might be associated with a
  tumor, usually benign but sometimes malignant.  They can also be a
  sign of dietary problems or a vaccine reaction.  Have any swelling
  or lump checked out and probably removed by your vet, and have
  anything that's removed sent to a pathologist.  For more
  information, see the Ferret Medical FAQ on Skin Tumors [1.1].

Difficulty using the hind feet, awkward gait, lack of movement
  Most often a sign of an adrenal or islet cell tumor (insulinoma), or
  arthritis, in older ferrets.  Could also be an injured back, the
  result of having been stepped or sat upon, closed in a door, or the
  like.  Ferrets have very flexible spines, but they're easily
  injured.

  Says Dr. Bruce Williams, DVM, about hind-end awkwardness:

     This is a common finding in older animals of many species - the
     most common cause is a mild degeneration of the nerves in the
     spinal cord or those innervating the legs.  In most of these
     cases, there is nothing to be done, but it also rarely results in
     paralysis, just variable amounts of weakness.

Overheating
  Ferrets do not tolerate high temperatures well at all.  They (like
  any pet) should NEVER be left in a hot car, and if you're keeping
  them outdoors be sure to provide some shade and plenty of water in
  summer.  Allowing them to sleep under hot radiators is probably also
  a bit risky.  Temperatures as low as the 80's can be life-threatening
  to ferrets without shade and cool water [10.8].

Loose skin and dull eyes
  Generally caused by dehydration, which is quite serious in  such
  a small animal.  Get your ferret to drink more, take him to a vet for
  subcutaneous fluids, and look for the underlying cause.

Unexplained hair loss
  Not the usual seasonal shedding, which should happen twice a year
  (but the times may vary due to indoor lighting conditions), but a
  severe loss, especially if more than the tail is affected [10.6].

Seizures
  It's pretty obvious that these indicate some kind of problem.  Most
  often the result of insulinomas in the pancreas causing
  extremely low blood sugar, but there are many other causes too.

Diarrhea [10.4]
  This can be serious, since ferrets are easily dehydrated.  Diarrhea
  may be caused by milk products, which contain lactose that ferrets
  do not tolerate well, or by a number of diseases.  A green or orange
  color or a bit of mucus just means the food didn't spend the usual
  amount of time in the digestive system, not that it's necessarily ECE
  (Epizootic Catarrhal Enteritis, or the "Green Diarrhea Virus"),
  but for more information on that, see the Ferret Medical FAQ on ECE
  [1.1].

  One thing you can try for mild cases, especially after consulting
  your veterinarian, is Pepto Bismol.  Most ferrets don't like the
  taste of the liquid, but you can give them 1/15th of a tablet
  crushed up in food instead.  A compounding pharmacist can also
  prepare the medication in Pepto Bismol in a different suspension to
  minimize or mask the taste.  Call 1-800-331-2498 to locate the
  nearest compounding pharmacist.  Dr. Mike Dutton suggests the
  prescription anti-diarrheal medication Amforol for cases that Pepto
  Bismol doesn't help.

Vomiting
  Ferrets do sometimes vomit from excitement, stress, a change of
  diet, or overeating, but if it's repetitive or if there are any
  signs of blood, get to a vet.  During shedding season ferrets may
  "spit up" a bit due to hair in the throat.  This can be helped with
  Petromalt [6.2]. 

Sneezing, runny nose, watery eyes, lethargy
  Yes, ferrets catch human flu.  They'll generally rest and drink a
  lot.  A visit to the vet would probably be a good idea, particularly
  if the flu looks bad or lasts more than a few days.  According to
  Dr. Susan Brown, "The antihistamine product Chlor-Trimeton may be
  used at 1/4 tablet 2 times daily for sneezing that may interfere
  with sleeping or eating."

Broken tooth
  If only the tip is broken, the tooth may discolor slightly, but it's
  nothing to worry about.  A more extensive break will cause pain, a
  definite unhealthy look to the tooth, and possibly gum problems, and
  should be treated (probably root canal or removal) by a vet or a
  veterinary dentist.

Persistent hacking or coughing
  An occasional cough might be caused by dust or swallowed fur, and
  can be treated with a bit of cat hairball preventative.  A cough
  from a cold can be treated with children's cough medicine; ask your
  vet for a recommendation and dosage.  A persistent cough is most
  likely a respiratory infection, probably viral.  A fever, yellow or
  green discharge from the eyes or nose, or congestion indicate a
  bacterial infection.  In either case, see a vet.  Another
  possibility is cardiomyopathy.  For more information, see the Ferret
  Medical FAQ on Cardiomyopathy [1.1].

Swollen vulva
  In an unspayed female, she's probably going into heat, especially if
  it's springtime.  For young spayed ferrets, under 18 months or so,
  the most common problem is pieces of the ovary that were missed in
  the spaying and have begun to produce hormones.  These pieces might
  be scattered around the abdomen.  For older ferrets, however, by far
  the most common cause of a swollen vulva is adrenal disease, usually
  cancer.  For more information, see the Ferret Medical FAQ on Adrenal
  Disease [1.1].

Return to whole male behavior (in a neutered male)
  The most common reason for a neutered male to try to mate, dribble
  urine or mark his areas, become aggressive, or have erections is
  unusual hormone production caused by adrenal disease.  For more
  information, see the Ferret Medical FAQ on Adrenal Disease [1.1].
  Other possibilities include cryptorchidism (a testicle which never
  descended into the scrotum and so wasn't removed) or bladder stones.
  The treatment for any of these is surgery.