Canine Von Willebrand's Disease
By Tenna Perry

Von Willebrand’s isn’t so much a disease as a condition. Of all
the inherited bleeding disorders in animals (and humans) it is
the most common. The defect isn’t autosomal (sex linked) so both
males and females can suffer from the “disease.” It must be
remembered that just because a dog doesn’t show symptoms of von
Willebrand’s, it doesn’t mean it can’t be a carrier.


Von Willebrand’s was discovered in humans and called a “disease”
in the 1920s by a Finnish doctor coincidentally named, von
Willebrand. After further research, he was able to figure out the
illness was actually linked to a missing factor in the blood’s
clotting ability.

Modern research has found von Willebrand’s doesn’t lower the
number of platelets (the factor in the blood that causes
clotting) but changes the platelet’s actual make up. Researchers
have discovered there are twelve “factors” that go into the
platelet’s make up and allows them to work properly. They have
set up a “Cascading Clotting Tree” to mark and show the different
factors. Von Willebrand’s affects Factor 8 on this tree.

There is a large, multimeric glycoprotein that is labeled as vWF.
This glycoprotein circulates in the plasma and is required for
platelet adhesion. When there is a defect in the vWF gene, there
is an insufficient synthesis of the vWF glycoprotein. This
insufficiency causes the platelets to fail in their adhesion or
“sticking together.” Like water coming through a damn with a hole
in it, the platelet “leaks” and bleeding continues.

Von Willebrand’s seldom happens in cats but it is very common in
various breeds of dogs. In all, some sixty different purebred
breeds have been commonly linked to von Willebrand’s with the
Doberman Pinscher having the highest incidence. Clinical trials
conducted on 15,000 Dobermans showed seventy percent of them were
carriers of the disease. Of these 15,000 Dobermans, the majority
of them didn’t show clinical signs. Another study estimated
68%-73% of Dobermans had the disease

Although Dobermans are the most commonly affected by von
Willebrand’s Disease, they usually have the milder forms. It is
also one reason Dobermans have such a lower survival rate of
diseases such as Parvovirus, which attacks the gastro-intestinal
tract and causes bleeding.

Other breeds that have a high incidence of von Willebrand’s
disease are Shetland sheepdogs, Scottish terriers, Airedale
terriers, Bassett hounds, Dachshunds, German shepherds,
Keeshonds, Corgies, Rottweilers, Poodles, Schnauzers and Golden
retrievers.

Often von Willebrand’s will show no clinical signs until the dog
begins bleeding for some reason. This reason could be something
as simple as a nail trim, spay or neuter or a heat cycle in
females or even teething in a puppy. While some dogs never show
clinical signs of the disease, others may have nosebleeds or
vaginal or penile bleeding. Bleeding from the urinary tract, gums
or other mucous membranes and hemorrhaging under the skin are all
common symptoms of von Willebrand’s Disease. Females with von
Willebrand’s may experience excessive bleeding after whelping
(giving birth).


There are three classifications of von Willebrand’s disease:


Type I – low vWF concentration. This is the most common of types
and is typical of Dobermans, Airedales and at least one-third of
Shelties. The clinical symptoms may vary in severity.


Type II –Uncommon form of von Willebrand’s that is attributed to
German Shorthaired Pointers.


Type III – The most severe of types. It has the highest
deficiency of vWF and is a typical defect in Scotties, Chesapeake
Bay retrievers and the remaining two-thirds of affected Shelties.


Studies have shown hyperthyroidism may raise the risk of bleeding
complications in animals that have von Willebrand’s Disease.


To diagnose von Willebrand’s Disease a veterinarian will often
conduct a CBC (complete blood count), urinalysis, blood clotting
time or a “buccal mucosal” screening time. The buccal mucosal
bleeding time uses a test strip that is tied around the maxilla
(upper jaw) that then causes engorgement in the folded-back area.
Normal blood clotting time is somewhere between 1.5 to 2.6
minutes.

It is interesting to note many Dobermans and other high risk
breeds may go through routine ear trims, tail docks, early spays
or neuters and show no signs of von Willebrand’s then at a much
later time in their life show the classic symptoms.

There is no cure for von Willebrand’s but there are some
precautions an owner can take to reduce the risks to their dog.
Avoid drugs that are known to inhibit platelet functions. Aspirin
is a prime example of one of these drugs. Others include
antihistamines, sulfa- or penicillin based antibiotics,
Ibuprofen, the tranquilizer phenothiazine, heparin and
theophylline.

Veterinarians have found that thyroid supplementation can lower
the tendency in some dogs to bleed while raising the level of vWF
concentration.

There is also a drug called DDAVP that can also increase the vWF
protein concentration although the response to the drug is
variable. It has been shown to raise the concentration in dogs
that do not have von Willebrand’s disease. The use in these dogs
may not be apparent until it is realized it takes a dog to donate
blood for a transfusion to another dog. In case of an emergency
or severe trauma, this donated blood is often the only thing that
can save the dog’s life.

For owners of breeds that are more prone to having von
Willebrand’s disease, there is a specialized test that can
determine the exact amount of the von Willebrand protein that is
present in the blood. If the test comes back positive for the
disease, it won’t necessary help the dog on a daily basis but
will come in handy to know if the dog ever requires emergency
treatment or undergoes any type of surgery.

Von Willebrand’s disease isn’t an automatic death sentence to
dogs. Many of the dogs that have the condition will live normal
lives with no complications. For those that do show clinical
signs, there are always options for the owner to guarantee the
best quality of life the pet can have.

Written by Tenna Perry

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