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Von Willebrand Disease
Issue Description
Von Willebrand's Disease is a genetic bleeding disorder. Dogs affected with vWD will have a reduction in the amount or function of a blood protein which binds platelets to blood vessels. This blood protein is commonly referred to as Von Willebrand's Factor (vWF). The factor can come from plasma, endothelial cells, or the subendothelium. The absence or deficiency of the factor can be life threatening by leading to uncontrolled bleeding episodes. It is a complex and difficult disorder to deal with, because genetics, diagnostic abnormalities, and sometimes-conflicting clinical signs are all involved.
Von Willebrand's Disease is a genetic bleeding disorder. Dogs affected with vWD will have a reduction in the amount or function of a blood protein which binds platelets to blood vessels. This blood protein is commonly referred to as Von Willebrand's Factor (vWF). The factor can come from plasma, endothelial cells, or the subendothelium. The absence or deficiency of the factor can be life threatening by leading to uncontrolled bleeding episodes. It is a complex and difficult disorder to deal with, because genetics, diagnostic abnormalities, and sometimes-conflicting clinical signs are all involved.
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Other Names
vWD
Breeds At Risk
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:
Corgi, Poodle (std & min), Scottie, Golden Retriever, Doberman, Sheltie, Akita, Cairn Terrier. Other breeds with a known prevalence of vWD in excess of 15% include
Basset Hounds, Dachshunds (mini & std), German Wirehaired Pointers, German Shepherds, Keeshonds, Manchester Terriers (std & toy), Miniature Schnauzers, and
Rottweilers.
Type II vWD is characterized by a low concentration of an abnormal vWF. Breeds in which severe type II-like vWD has been diagnosed include American Cocker Spaniels,
German Shorthaired Pointers, and German Wirehaired Pointers.
Type III vWD is essentially the complete absence of vWF. Severe type III vWD has been diagnosed in Australian Cattle Dogs, Chesapeake Bay Retrievers, Fox
Terriers (toy), German Shepherds, Scottish Terriers, and Shetland Sheepdogs.
Symptoms
The clinical signs of vWD are typical of a platelet function defect, such as spontaneous hemorrhage for mucosal surfaces, epistaxis, hematuria, melena and excessive hemorrhage from surgery or trauma. Stillbirths, neonatal deaths, prolonged bleeding at tail docking, ear cropping or dewclaw removals are other common manifestations.
vWD
Breeds At Risk
Symptoms
The clinical signs of vWD are typical of a platelet function defect, such as spontaneous hemorrhage for mucosal surfaces, epistaxis, hematuria, melena and excessive hemorrhage from surgery or trauma. Stillbirths, neonatal deaths, prolonged bleeding at tail docking, ear cropping or dewclaw removals are other common manifestations.
Bleeding from gums, excessive umbilical cord bleeding at birth, excessive bleeding from toenails cut too short, and bleeding after elective
procedures. Some other clinical signs are: bloody stools, feces, hematochezia , forelimb lameness, forelimb swelling, generalized lameness or stiffness, head, face,
ears, jaw, nose, nasal, swelling, hematuria, hemorrhage of any body part or clotting failure, hind limb lameness, hind limb swelling, hyphema, neck swelling, pale,
pelvic or perennial swelling, petechiae or ecchymoses, red or brown urine, swelling skin or subcutaneous, swelling, mass external abdomen, tachycardia, thoracic
swelling. Not all dogs with vWD will show clinical signs.
Diagnosis
Diagnosis can be preformed by measurement of plasma concentrations of vWF. The blood test is called the Von Willebrand's Factor Assay also known as the Enzyme-Linked Immunosorbent Assay (ELISA). This blood test is preformed at a Veterinary Hospital and then sent into a laboratory for a rating of vWF. Daily variation in vWF can be high, so multiple measurements may be necessary to establish the Von Willebrand status of a dog. Hematology Laboratory of Cornell University established the following ranges:
Normal range: 70-180% *Considered to be free from vWD, and are unlikely to transmit the disease
Borderline range: 50-69% *Is equivocal, cannot be classified definitively but may be clinically or genetically significant.
Abnormal range: 0-49% *May or may not be clinically expressed but are diagnosed as carriers of vWD and can transmit the trait to offspring.
It is believed that dogs testing less than 30% vWF have an approximately 75% chance of having the clinical signs for vWD expressed. And dogs testing above 30% have a 25% chance of expressing clinical signs.
Treatment
The primary treatment for von Willebrand's disease is the administration of blood or blood products to patients with active or anticipated bleeding episodes. A blood product called cryoprecipitate contains large amounts of von Willebrand factor, but it is seldom available. More commonly, the veterinarian will use fresh plasma, or plasma that was frozen immediately after collection and then thawed. Whole fresh blood may be used if hemorrhage has been severe.
The administration of a drug called DDAVP may be helpful in preventing hemorrhage in some affected animals if it is given prior to the time that bleeding occurs. This drug increases levels of von Willebrand factor available for the clotting process. DDAVP can also be given to dogs donating blood prior to blood collection, so that samples with high von Willebrand factor activity can be obtained. Not all dogs respond to DDAVP.
Care & Prevention
Provide soft padded areas for your dog to lie on. Minimize the chance of injury by observing and fixing any sharp corners, such as on doggie doors. It is usually not necessary to limit activity as spontaneous bleeding is not common. If your dog should begin bleeding, seek veterinary assistance immediately.
Because it is a hereditary disease, an animal born with vWD cannot be cured.
Minimize the chance of injury by keeping your dog confined either in a fenced area or on a leash when outdoors. If your dog should begin bleeding, seek veterinary assistance immediately.
Inform any veterinarian treating your dog about his vWD. This is especially important prior to surgical procedures. Inform any groomer handling your dog about his condition; they will use extra care in clipping and trimming nails and can be prepared if a cut occurs.
Since the disease is hereditary, the ideal way to eliminate it would be to avoid breeding affected dogs. However, not all dogs with low von Willebrand's factor concentrations have significant bleeding. The mere fact that the concentration is low does not always mean that clinically significant problems will occur, even in breeds in which a significantly high number of dogs have reduced von Willebrand's factor. If all dogs that tested low for the factor were eliminated from breeding, then breeding programs would be quite restricted. Certainly, though, it makes sense not to breed dogs that have had clinically significant episodes of bleeding due to von Willebrand's disease, no matter what their breed.
In an affected dog, problems may be avoided prior to elective surgeries by remembering to screen for this condition, especially if previous bleeding episodes have occurred or if there is a familial history of bleeding. Pre-treatment with DDAVP may help avert disastrous consequences, as will having blood products on hand in case they are needed.
Diagnosis
Diagnosis can be preformed by measurement of plasma concentrations of vWF. The blood test is called the Von Willebrand's Factor Assay also known as the Enzyme-Linked Immunosorbent Assay (ELISA). This blood test is preformed at a Veterinary Hospital and then sent into a laboratory for a rating of vWF. Daily variation in vWF can be high, so multiple measurements may be necessary to establish the Von Willebrand status of a dog. Hematology Laboratory of Cornell University established the following ranges:
It is believed that dogs testing less than 30% vWF have an approximately 75% chance of having the clinical signs for vWD expressed. And dogs testing above 30% have a 25% chance of expressing clinical signs.
Treatment
The primary treatment for von Willebrand's disease is the administration of blood or blood products to patients with active or anticipated bleeding episodes. A blood product called cryoprecipitate contains large amounts of von Willebrand factor, but it is seldom available. More commonly, the veterinarian will use fresh plasma, or plasma that was frozen immediately after collection and then thawed. Whole fresh blood may be used if hemorrhage has been severe.
The administration of a drug called DDAVP may be helpful in preventing hemorrhage in some affected animals if it is given prior to the time that bleeding occurs. This drug increases levels of von Willebrand factor available for the clotting process. DDAVP can also be given to dogs donating blood prior to blood collection, so that samples with high von Willebrand factor activity can be obtained. Not all dogs respond to DDAVP.
Care & Prevention
Provide soft padded areas for your dog to lie on. Minimize the chance of injury by observing and fixing any sharp corners, such as on doggie doors. It is usually not necessary to limit activity as spontaneous bleeding is not common. If your dog should begin bleeding, seek veterinary assistance immediately.
Because it is a hereditary disease, an animal born with vWD cannot be cured.
Minimize the chance of injury by keeping your dog confined either in a fenced area or on a leash when outdoors. If your dog should begin bleeding, seek veterinary assistance immediately.
Inform any veterinarian treating your dog about his vWD. This is especially important prior to surgical procedures. Inform any groomer handling your dog about his condition; they will use extra care in clipping and trimming nails and can be prepared if a cut occurs.
Since the disease is hereditary, the ideal way to eliminate it would be to avoid breeding affected dogs. However, not all dogs with low von Willebrand's factor concentrations have significant bleeding. The mere fact that the concentration is low does not always mean that clinically significant problems will occur, even in breeds in which a significantly high number of dogs have reduced von Willebrand's factor. If all dogs that tested low for the factor were eliminated from breeding, then breeding programs would be quite restricted. Certainly, though, it makes sense not to breed dogs that have had clinically significant episodes of bleeding due to von Willebrand's disease, no matter what their breed.
In an affected dog, problems may be avoided prior to elective surgeries by remembering to screen for this condition, especially if previous bleeding episodes have occurred or if there is a familial history of bleeding. Pre-treatment with DDAVP may help avert disastrous consequences, as will having blood products on hand in case they are needed.
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