Dog von Willebrand Disease – vWD
Von Willebrand Disease (vWD) is the most common inherited bleeding disorder. This platelet defect results in platelet dysfunction. A deficiency of the von Willebrand factor (vWF) causes the condition linked to a missing factor in clotting. The vWF is the large multimeric glycoprotein that helps blood platelets (thrombocytes) adhere to the damaged blood vessel lining (endothelium) and possibly improve clot formation. A temporary plug slows the blood loss. An enzyme activates clotting factors and form fibrin that encloses the platelet plug for a permanent clot. Canines with abnormally low levels of vWF may have a slow forming plug. A defective vWF gene may result in platelets failing to adhere. As the platelet leaks, bleeding continues. Prolonged bleeding after injury may occur.
This condition affects any of sixty canine breeds. Certain breeds seem to more susceptible: Doberman Pinschers, Rottweilers, Welsh Corgis, Poodles, Shetland Sheepdogs, German Shepherd Dogs. Scottish Terriers seem to experience the more severe form.
Symptoms and Diagnosis
Both males and female canines may inherit vWD. Although some dogs show no clinical symptoms, common signs include bleeding from the urinary tract, vaginal or penile bleeding, gums, mucus membranes and haemorrhaging. Puppies may experience bleeding while teething. Bleeding could result from a nail trip, spay or neuter. Small or superficial wounds may show prolonged bleeding. Females may bleed excessively after whelping. Other symptoms include nosebleeds, multiple small bruises, and blood in stool. Excessive bleeding can result in anemia, shock and death. Dogs not affected by vWD can pass this defect to offspring.
Diagnosis may be made through a new blood test that detects amounts of vWF with greater accuracy. This test can predict if the dog will carry the disease or be affected. Measuring the vWF in serum shows an abnormal result if less than 49%. Urinalysis and blood clotting time, antigenic measurement with quantitative ELISA assays and multimeric assays can provide further diagnosis.
Classification of vWD as Type I, Type II or Type III can suggest therapeutic treatment.
No cure exists for this condition as yet. Treatment so far can include the administration of the von Willebrand Factor, or complete plasma. Canines with a mild form can still enjoy a long life. Dogs with late-onset vWD with hypothyroidism may find that treatment with thyroid-hormone supplementation can reduce bleeding and raise the concentration of vWF.
For congenital cases, owners should concentrate on injury prevention. Owners should now allow dogs to chew on sticks or sharp bones or play rough with other dogs. Dogs with bleeding gums should eat soft food.
Diagnosis can alert the veterinarian if medication is required to increase the dog’s level for vWF for the short term prior to surgery to reduce bleeding. For emergency treatment that addresses bleeding episodes, a transfusion can supply more active vWF.
Preventing the passing of this inherited bleeding disorder calls for removing any affected dogs from a canine breeding program.