Von Willebrand’s Disease
by Margot Schwag, VMD
** Permission of author is required for use of this article.**
Von Willebrand’s Disease (vWD) is the most common inherited bleeding disorder in dogs. Hemorrhage in affected pets is caused either by a deficiency or dysfunction of a protein essential for the control of bleeding. The protein acts on the surface of platelets to make the platelet more sticky or adhesive to plug holes in blood vessels. Without the protein or platelets, the leak will not be sealed and the dog will continue to bleed.
Although Dobermans are probably the most commonly affected breed, the disease exists in more than 50 different breeds. Most prevalent other than Dobes are the Pembroke Welsh Corgi, Scottish Terrier, Cairn Terrier, Shetland Sheepdog, Golden Retriever, Standard and Miniature Poodles, and Akitas. As of 1993, 71% of Dobes carry the vWD gene in their DNA. Of those, 10-20% have had a history of a bleeding incident.
Detection of vWD consists of a simple blood test. The test measures the amount or function of the vWF protein. The best test is the Von Willebrand’s Factor antigen test (vWF:Ag). The amount of vWF in a test plasma sample is measured and then reported as the vWF:Ag%. The normal range is from 70-180% vWF:Ag; borderline range is from 50-60%; abnormal range is from 0-49%. The percentage is compared to a pooled standard control plasma from healthy, normal dogs. The test alone cannot distinguish asymptomatic carriers of vWD from “bleeders”. Medical history and results of bleeding time tests in addition to the vWF:Ag test are needed. Testing also cannot distinguish between inherited and acquired types of vWD.
VWD can be a primary congenital problem inherited at birth from one or both parents. Carriers of this genetic defect may show no signs until some other stressful event compromises the ability of the body to form blood clots. An acquired form of the disease also exists. In this case, vWF production and function are decreased secondary to another disease process, i.e. hypothyroidism, concurrent bacterial viral infection, estrus (heat), pregnancy, or steroids, etc.
Few vWD affected animals have severe problems. Even fewer die. Bleeding episodes may be worsened by physical, emotional, or physiological stress as well as disease.
Signs of vWD include spontaneous bleeding from the mucous membranes lining the nose, mouth, digestive, urinary, and reproductive tracts. Excessive bleeding may also occur after nail trims, teeth extractions or sites of trauma or surgery. In many instances the bleeding can be internal so that the owner may not even be aware of any problems until a large painful bruise appears or the dogs gums become very pale. Hemorrhage may also occur within the central nervous system and if severe enough, sudden death ensues.
Preventive measures for dogs affected with vWD include local treatments of wounds and hormonal supplementation (thyroxin, a replacement thyroid hormone) since many dogs with the acquired form of vWD are hypothyroid also. Drugs or vaccines known to affect platelet function should be avoided, i.e. aspirin. Platelet and vWD:Ag are essential for clot formation. A vWD comprised dog may be okay as long as platelet function is normal, should platelet function be affected as well, the pet may have a profound bleeding incident.
Treatment of a bleeding episode involves replacing the vWF protein via a transfusion. If there has been extensive blood loss, whole blood, which includes red blood cells and plasma, is required. With minimal blood loss but chronic seepage of small amounts of blood, the episode can be corrected with a plasma transfusion.
Eradication of vWD depends solely on selective breeding practices. Simply stated, all animals to be used for breeding should be tested for vWF:Ag. Only those dogs in the normal range should be used in a breeding program. It is not recommended to breed carriers of vWD.
Dogs diagnosed as bleeders or carriers can look forward to many happy, healthy years provided the owners are aware of the disorder and take proper steps should an unlikely bleeding episode occur.
Author’s note: One of my dogs is a clinical bleeder which we found out when he was neutered. My other dog is a carrier, and was spayed as a result with no problems with bleeding. My third dog is normal for vWD. I would never reject adopting a dog based on it’s vWD status.
Reprinted from March 1997 issue of DOBERMAN DISPATCH with permission of Dr. Margot Schwag, VMD and Doberman Pinscher Rescue of PA, Inc., One Melvin Road, Phoenixville, PA 19460-4426.