VON WILLEBRAND'S DISEASE
What is von Willebrand's disease?
von Willebrand's disease (vWD) is the most common inherited bleeding disorder
of both man and animals. It is caused by a deficiency in the amount of a protein
needed to help platelets (a blood cell used in clotting) seal broken blood vessels.
The deficient protein is called "von Willebrand factor antigen".
Which breeds are most commonly affected by vWD?
About 30 different breeds are known to be affected but the Doberman is the
breed most commonly associated with this disease. Of 15,000 Dobermans screened,
more than 70% were found to be carriers of the disease in the United States.
Fortunately, most of these are not clinically affected (i.e. we see no evidence
of bleeding). However, the number of Dobermans with a history of bleeding appears
to be on the increase. Although Dobermans are commonly affected, they usually
have the mildest form of the disease. Dobermans are, on average, four years-old
before diagnosis is made.
One study showed that 30% of Scottish Terriers and 28% of Shetland Sheepdogs
had abnormally low concentrations of von Willebrand factor. The German Shepherd
Dog can also be affected with the disease.
What are some of the signs of vWD?
Many dogs with vWD never show outward evidence of having the disease. Others
may hemorrhage from the nose, vagina, urinary bladder or oral mucous membranes;
prolonged bleeding after trauma or surgery is common. Females may bleed excessively
while in estrus or after giving birth. In affected dogs with uncontrolled hemorrhage,
death may occur.
How is vWD diagnosed?
A screening test, called the buccal mucosal bleeding time, may be performed
by your veterinary surgeon. Prolonged bleeding on this test can raise the suspicion
of the disease, especially in breeds known to be at risk. For owners who wish
to confirm the diagnosis, it is possible to determine the exact amount of von
Willebrand protein present in the blood.
Owners of Dobermans often report that the pet has undergone routine ovariohysterectomy
(spay) or castration, or trim, and tail docking as a pup. An uncomplicated recovery
from such procedures does not eliminate the possibility that a dog may be affected;
some dogs do not become obvious "bleeders" until later in life.
Are there any situations which pose an increased risk if my dog is affected?
The avoidance of certain medications is critical for the dog with vWD. Drugs
that may precipitate a bleeding crisis in the dog include the following:
- Phenothiazine tranquilizers
- Sulfur-based antibiotics
These drugs should be avoided when possible, but especially if the dog is
in a bleeding crisis.
Emotional stress is thought to precipitate bleeding in humans with the disease.
The subjective nature of such a finding makes it difficult to know if there
is a similar association in dogs but it remains a possibility.
What can be done to treat dogs with vWD?
In an emergency situation, transfusion of blood or fresh frozen plasma may
stabilize the patient. The dog donating blood may be treated with a drug called
DDAVP prior to blood collection which will raise the level of von Willebrand
factor in the donor's blood, an obvious benefit to the recipient.
Some dogs with vWD are able to increase the amount of protein in circulation
after the administration of DDAVP, although the response is variable. At this
time, it is not recommended to use this drug on a regular basis. The drug is
expensive, and not all dogs will respond.
If I own a Doberman that has always been healthy, should I do something?
Since many affected Dobermans will never have bleeding problems, any recommendation
to do routine testing is debatable. However, identification of dogs that have
abnormal bleeding times can be very valuable if surgery is planned. Additionally,
knowing that your dog is a carrier of vWD can be very important if an injury
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