Von Willebrand's disease (VvWD) is an inherited bleeding
disorder. It is a complex and difficult disorder to deal
with, because genetics, diagnostic abnormalities, pathogenic
mechanisms, and sometimes conflicting clinical signs are all
involved. The commonality between all vWD is a reduction in
the amount or function of von Willebrand factor (vWF), which
is manifested through abnormal platelet function and
prolonged bleeding time. The vWF factor is a blood protein
which binds platelets to blood vessels when they are
injured. Absence or deficiency of the factor can, therefore,
lead to uncontrolled bleeding episodes. In dogs, the most
common clinical signs are spontaneous bleeding from the gums
or nose, blood in the urine or gastrointestinal tract, or
excessive bleeding at the time of surgery. Clinical signs
also include epistaxis, prolonged estrus or postpartum
bleeding, hematuria, melena, excessive bleeding after
toe-nail cutting and sometimes hemorrhaging into body
cavities and organs.
Diagnosis can be performed by measurement of plasma
concentrations of vWF. TESTING SHOULD BE DONE AT AN EARLY
AGE SINCE THE DISORDER OFTEN DIMINISHES WITH AGE, CAUSING
FALSE-NEGATIVE TEST RESULTS IN OLDER ANIMALS. Additional
screening tests such as bleeding times or platelet
agglutination assays can also be performed. Precautions
should be taken before surgery, so it is important to let
your veterinarian know of bleeding problems in the past.
Different breeds exhibit different variations of the
disease, and some individual animals appear to "acquire" vWD.
While the bulk of the information available is based upon
purebred dogs, the disease is not unknown in mixed breeds.
The total number of breeds affected by vWF exceeds 50. The
disease also appears in cats, pigs, horses, and humans.
Human variants of vWD are broken into three main types
which can be used to describe canine vWD. Type I vWD is
characterized by a low concentration of normally structured
protein. In screening studies done at Cornell over a period
of years (1982-1992), percentages of dogs of some breeds
tested as carrying the disease, and with concentrations of
vWF less than 50% of standard (considered to be at risk)
were the following breeds: Corgi, Poodle (std. and min),
Scottie, Golden Retriever, Doberman, Sheltie, Akita, Cairn.
Other breeds with a known prevalence of vWD in excess of
15% include Basset Hound, Dachshund (mini & std), German
Wirehaired Pointer, German Shepherd, Keeshond, Manchester
Terrier (std & toy), Miniature Schnauzer, and Rottweiler.
Type II vWD is characterized by a low concentration of
abnormal vWF. Breeds in which severe type II has been
diagnosed include American Cocker Spaniel, German
Shorthaired Pointer, and German Wirehaired Pointer.
Type III vWD is essentially the complete absence of vWF.
Severe type III vWD has been diagnosed in Australian Cattle
Dog, Chesapeake Bay Retriever, Fox Terrier, German Shepherd,
Scottie, and Shetland Sheepdog.
In vWD dogs, bleeding can be spontaneous, usually from
the mucosa of the mouth, nose, or gastrointestinal tract.
Injury that is accompanied by bleeding may continue unabated
until a transfusion is administered. Whether or not bleeding
from small wounds will stop without treatment is not
predictable.
Living with one of these affected animals can get quite
interesting. Because this disease can be eradicated before
breeding (by having your dog tested) it can be eradicated.
Unfortunately, experience and hearsay indicate that the AKC
is not active in the enforcement of these preventive
measures. Apparently the breeders, at least some of them are
not either. Testing prior to breeding is a must.
For those who wish additional information, an excellent
source concerning the disease is Ettinger's Textbook of
Veterinary Internal Medicine.
Sources: Ettinger's Textbook of VIM; Sue Tornquist, DVM,
Veterinary Clinical Pathologist, Dept. of Vet. Micro
Pathology, Washington State Univ; Gary Mason, Research
Manager, Interleaf, Inc. Waltham, MA.
