Von Willebrand disease in dogs is a bleeding disorder that can take a variety of forms, fortunately often benign.
Although most dogs with this condition have no symptoms, or only mild ones, it is still essential to screen dogs that are highly susceptible to it, such as the gentle Doberman.
Knowing their condition can save these dogs from unnecessary health risks, especially preventive surgeries, which then become risky. Also, screening allows us to exclude affected dogs from reproduction, so that they do not spread their disease and, above all, do not give birth to sick or even non-viable puppies.
What is Von Willebrand Disease in dogs?
Von Willebrand disease in dogs is an inherited bleeding disorder consisting of a blood clotting disorder. It should not be confused with hemophilia, which does not result from the same coagulation deficiencies, although it is similar in its symptoms. In fact, it is sometimes called pseudo-hemophilia.
Discovered in 1926 by Dr. Von Willebrand, this disease is caused by a qualitative or quantitative defect in a glycoprotein, Von Willebrand factor. Von Willebrand factor is synthesized by the endothelial cells of the blood vessels and the megakaryocytes, giant cells that produce platelets.
Platelets, or thrombocytes, are small cells that circulate freely in the blood and, in simple terms, plug holes in bleeding injuries: this is the phenomenon of coagulation. Von Willebrand factor plays, among other things, a key role in the connection between platelets and blood vessel cells during hemostasis (coagulation process).
In dogs, the disease was first discovered in 1970, and is consistent with the observation of a high prevalence of coagulation disorders in German Shepherds, Golden Retrievers, Dobermans and Dwarf Schnauzers. It is therefore suspected that the disorder is heritable and that excessive inbreeding within purebred lines is responsible for the spread of the disease in the dog population.
As in human medicine, veterinary medicine has classified Von Willebrand disease into three distinct types. Type I is the most common and least severe form of the disorder. There is an abnormally low level of Von Willebrand factor in the dog's blood, but not all affected animals consistently report symptoms.
Type II also has a low amount of Von Willebrand factor in the blood, but symptoms are more severe and do not respond to medication. Finally, Type III is the most severe form of the disorder and results in a complete absence of Von Willebrand factors. Fortunately, this is also the rarest form.
Causes of Von Willebrand Disease in dogs
The causes of Von Willebrand disease in dogs are genetic. The gene coding for the offending factor is located on chromosome 12, but the mutation involved has not been identified to date. In the Type I form, the mode of transmission is autosomal dominant. It mainly affects the Doberman and, to a lesser extent, the German Shepherd, the Miniature Poodle, the Miniature Schnauzer and the Golden Retriever.
A dog with the mutation is always ill, although the expression of the gene is variable and does not necessarily show symptoms. In dogs without symptoms of the disease, Von Willebrand factor deficiency is always present and can be observed by assay.
When no assay is performed, the disease is sometimes undetectable and asymptotic dogs are not always removed from breeding. This is particularly problematic since homozygous puppies (inheriting two disease genes, one from each parent) are usually not viable, except in the Doberman.
In the rare Type II form, the mode of transmission is probably autosomal recessive. Dogs carrying the genes involved are therefore not always ill, as the recessive gene does not express itself in the presence of a healthy dominant gene. As with Type I, there is a significant risk that a dog carrying the mutation will pass it on to its offspring, who will then develop the disease.
Type II Von Willebrand disease has so far only been described in the Pointer and the Drathaar. Type III Von Willebrand disease has an autosomal recessive inheritance pattern, similar to that of Type II.
A familial form exists in the Shetland Sheepdog, Scottish Terrier, Chesapeake Bay Retriever and Dutch Kooiker. Episodic cases have also been observed in the Border Collie, Labrador, Pomeranian, Bull Terrier and Cocker Spaniel.
Symptoms of Von Willebrand Disease
The symptoms of Von Willebrand disease vary depending on the type and expression of the gene involved. However, severe symptoms are extremely rare. Occasionally, bleeding from the skin and mucous membranes may occur, either spontaneously or following trauma, in which case the bleeding is disproportionate, i.e., abnormally large or long.
Although major bleeding can be fatal, it is rare and minor bleeding is the most common symptom of the disease. In susceptible dogs, Von Willebrand factor testing is recommended prior to surgery to better assess the risk/benefit ratio.
Treatment and Prognosis of Von Willebrand Disease
The treatment of Von Willebrand disease in dogs is palliative, combined with preventive measures to avoid bleeding, as the disease is currently incurable. To overcome the deficiency of Von Willebrand factors in the dog's body, two major methods are used: the supply of new factors or the stimulation of factor production.
The supply of new factors is done by blood plasma transfusions. Different types of transfusion exist, including whole blood, which is the most common, frozen plasma, which limits the risk of intolerance, and precipitated plasma enriched with factors, which limits the risk of hypervolemia. The choice of method used is based on cost, quantities required and availability of products - especially in an emergency.
Von Willebrand factor production can be stimulated with synthetic hormones. Desmopressin, a vasopressin analogue, is the most commonly used. Desmopressin causes the release of Von Willebrand factors stored in the endothelial cells of blood vessels into the bloodstream. Dogs with Type II and III disease do not respond to this treatment.
In dogs with Type I, factor stores are rapidly depleted, so treatment is sporadic. It is primarily used to prevent surgery. Thyroid hormone supplementation may also be indicated in dogs with hypothyroidism, which may be involved in the development of Von Willebrand disease.
Finally, preventive measures should be taken to avoid bleeding. Rough play, fighting and walking through thorny bushes should be avoided. The ingestion of blunt objects (pieces of bone or toys) should be avoided at all costs. Medication intake should also be carefully monitored, as some treatments with anticoagulant properties can significantly worsen the problem.
Similarly, preventive surgeries, such as sterilization, should be avoided if the benefit/risk ratio does not seem optimal. In general, the prognosis for dogs with Type I Von Willebrand disease is very good, but the prognosis for dogs with Type II or III is much more guarded.
How do I know if my dog has Von Willebrand disease?
Von Willebrand disease in dogs is primarily manifested by spontaneous bleeding from the mucous membranes (gums and nose), but many dogs have no symptoms. It is advisable to screen dogs with a high susceptibility to this condition so that preventive measures can be taken if necessary. In particular, it is important to be well prepared for possible surgical procedures, which could go wrong if there is no unexpected coagulation.
Can Von Willebrand disease be treated in dogs?
Von Willebrand disease cannot be cured, but it can be controlled. Blood transfusions and hormone treatments can be used sporadically to raise the level of deficient factors in the dog's blood, and preventive measures are often effective in avoiding tragedy. On a daily basis, it is advisable to avoid activities that could cause external or internal bleeding (fights, rough games, chewing bones that could be swallowed...).
Which dogs are prone to Von Willebrand disease?
The Doberman is without question the dog most prone to Type I Von Willebrand disease. Fortunately, it often has a mild form of the disease. The German Shepherd, the Miniature Poodle, the Miniature Schnauzer and the Golden Retriever are also over-represented in the Type I form. Type II appears to be limited to the Pointer and Drathaar, and Type III is most common in the Shetland Shepherd, Scottish Terrier, Chesapeake Bay Retriever and Dutch Kooiker.
My dog has Von Willebrand disease, is it serious?
Von Willebrand disease is most common in its Type I form, which is not very serious, but should be monitored. Usually, a few preventive measures are enough to avoid tragedy, and the dog lives a normal life. The rare Type II and Type III forms are more serious and have a much more guarded prognosis.
If your dog is prone to Von Willebrand disease, especially if it is a Doberman, we strongly recommend that you consult a veterinarian to determine whether or not it has the disease. In fact, knowing your dog's condition is essential to prepare him for any surgery, such as a simple sterilization, but also to avoid unnecessary risks in his daily life.
With a few simple preventive measures, a dog with Von Willebrand Disease can usually live his or her life like any other dog, without suffering too much from his or her little bleeding problem.