posted 07-29-2003 02:28 AM         

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.