What is von Willebrand’s Disease in Dogs?
What is von Willebrand’s disease in dogs? What are the symptoms, and can anything be done? Keep reading to find out more!
When we get a cut or injury somewhere, blood will start flowing. The first thing that needs to happen is the coagulation of the blood – the solidification of the blood – and the closing of the associated vessels.
Both happen as part of the hemostasis system. Without the hemostasis, the blood would continue flowing, which is why it is essential to preserve life.
But sometimes, the hemostasis doesn’t function as intended – this is called a disorder of hemostasis. Von Willebrand’s Disease (vWD) is the most common inherited disorder of hemostasis in dogs and is due to an abnormality or deficiency in the von Willebrand factor.
Classifying vWD in Canines
Von Willebrand’s disease in dogs is an inherited bleeding disorder, also called a “thin blood disease.” The von Willebrand factor protein (vWF) is at the center of this disease. This vWF protein is constantly circulating within the bloodstream or is stored in the skin cells. When a blood vessel sustains an injury, vWF will be present to control the bleeding.
When a dog, or human, suffers from von Willebrand’s disease, there either isn’t enough vWF or the protein is damaged, both conditions resulting in the organism being unable to control the bleeding. The characteristics and biochemical clinical findings determine what type of von Willebrand’s disease a dog is suffering from.
Type 1 von Willebrand’s disease
Von Willebrand factor concentration is low, and its structure is normal. Clinical signs vary a lot between individuals. This is the type of von Willebrand’s disease that affects most breeds, including:
Amongst many others.
Type 2 von Willebrand’s disease
Von Willebrand factor concentration is low, and its structure is abnormal. Clinical signs are often severe. The breeds affected by this type are:
- German Shorthaired Pointer
- German Wirehaired Pointer
Type 3 von Willebrand’s disease
Von Willebrand factor concentration is severely reduced or completely absent. The clinical signs seen in this type are almost always severe. This type is due to an inherited recessive trait or a mutation in the vWF gene, depending on the breed. The breeds affected by this type are:
- Dutch Kooiker
- Shetland Sheepdog
The Diagnostic Ranges of von Willebrand’s Disease in Dogs
Owners of puppies of the afflicted breeds are likely to want them tested for von Willebrand’s disease at a young age. A blood test is necessary for this.
A veterinarian will test the blood test in a laboratory. The test in labs for von Willebrand’s disease includes the von Willebrand factor antigen assay – shortened into vWF:Ag. Essentially this test measures the concentration of vWF in a blood sample. The results then come out as %vWF:Ag and compared to 100%.
Plasma vWF levels fluctuate from day to day in healthy dogs and a bit more when a dog is pregnant, in heat, or suffering from systemic illness. However, there are levels of %vWF:Ag a healthy dog should not get below.
Diagnostic ranges of vWF:Ag is used to predict whether a specific dog is likely to be affected by vWF and is, therefore, an aid for predicting genetic status.
- Normal: 70 – 180 vWF:Ag %
- Borderline: 50 – 69 vWF:Ag %
- Anbormal: 0 – 59 vWF:Ag %
Dogs in the normal range are considered clear of classical vWD traits and at low risk of expressing or transmitting von Willebrand’s disease to any offspring. On the other hand, dogs in the borderline or abnormal range are much more likely to express the disease characteristics.
For a dog found to be in the borderline or abnormal ranges, it is vital to take steps to avoid bleeding, especially in cases where a dog needs surgery or is injured. Carriers of vWD should not be part of breeding as they are likely to pass on abnormal genes.
However, just because a dog is likely to carry the genes for vWD does not necessarily mean that it will certainly be sick or suffer excessive bleeding.
Von Willebrand Disease Symptoms
But what happens when a dog has von Willebrand’s disease? Many dogs with vWD never show any clinical signs of the disease. However, the most prominent symptom is a prolonged bleeding time because the blood vessels cannot close properly.
The disease is noted, in most cases, when the veterinarian notices prolonged bleeding after trauma or surgery or sees significant bruising after a routine procedure. Some dogs may also spontaneously bleed from the nose or other mucosal membranes, like those within the mouth.
The Causes of Von Willebrand Disease in Canines
The von Willebrand factor protein is a large protein and part of the hemostasis. It gets produced by endothelial cells and stored in platelets within the blood. Von Willebrand factor is the protein that initiates platelet adhesion to the endothelium within the blood vessels, initiating the closing of the holes and the blood coagulation in the area.
When the body cannot produce the von Willebrand factor correctly, the hemostasis cannot function properly or initiate itself correctly, causing the injured blood vessel to remain open for much longer and the blood flowing freely from them.
Therefore vWD is also called “thin blood disease.” Although it is not that the blood is thinner, not truly; it is more that the blood vessels cannot be closed after sustaining an injury – allowing the blood to keep flowing.
Diagnosing vWD in Dogs
Often, von Willebrand’s disease will be suspected if a patient suffers from prolonged bleeding. At first, your vet can do a screening test to rule in or out the risk of vWD. The screening test is also called a buccal mucosal time test – or the BMT.
For the BMT, a small cut is made in the cheek mucosa, and the time it takes for the bleeding to stop is recorded. If this time is prolonged, it increases the suspicion of vWD. If it is normal or even a little too quick, vWD is not likely.
If the BMT is prolonged, a von Willebrand’s disease test is necessary, and the vWF:Ag % is measured.
If the patient is suffering from increased bleeding time and has an abnormal vWF:Ag, a specific diagnosis of vWD can be made.
Von Willebrand Disease Treatment Options
Unfortunately, your veterinarian cannot cure von Willebrand’s disease in dogs. There are, however, things that are possible to limit the damages the disease can cause.
In patients suffering from severe bleeding, plasma transfusion can help control the symptoms by artificially supplying the blood with the von Willebrand factor. Whole blood is not as valuable as it does not contain enough vWF.
Also called DDAVP, it stimulates the release of vWF from stores within the body and endothelial cells, thereby increasing vWF:Ag% levels. This drug does not work in dogs suffering from vWD type 3, and repeated administration has limited effect as the stores experience depletion.
Who was Erik Adold von Willebrand?
Erik Adolf von Willebrand was a doctor from Finland who spent a great deal of his professional life from 1896 and onwards researching haematology – as well as metabolism, obesity, and gut health. He was also one of the first Finnish physicians who successfully used insulin to treat diabetic coma.
In 1924 von Willebrand managed to distinguish a bleeding disorder from the already known hemophilia, and the newly discovered condition was named after him: Von Willebrand’s disease.
Later on, other researchers discovered that vWD was due to a deficiency of a specific protein that was part of the hemostasis – the protein we now know as the von Willebrand factor.
Von Willebrand vs. Hemophilia in Dogs
Both diseases are known as bleeding diseases and can be pretty similar. Haemophilia is also an inherited disease that causes prolonged bleeding from areas like traumatic sites, mucosal areas, and surgery sites.
However, unlike vWD, hemophilia more commonly affects males as it is linked to the X-chromosome, whereas vWD affects males and females equally. Another big difference is also that hemophilia affects the coagulation factors VIII and IX within the hemostasis, and von Willebrand disease only affects the von Willebrand factor.
But, we forgive you for thinking these two diseases are quite similar, and both are important to know for any dog owner with a dog that bruises easily!
Canine Breeds Commonly Affected by vWD
Von Willebrand’s disease is first and foremost an inherited disease associated with an autosomal trait – meaning males and females transmit and express the genes with equal frequency.
All dogs have two von Willebrand genes, but not all of them will need two abnormal genes to be sick. In most dogs, the presence of even one abnormal vWF gene can be enough to cause abnormal and variable bleeding time.
The abnormal genes are often either due to a mutation in a specific gene associated with the von Willebrand factor or the deletion of some genes related to vWF. The breeds most commonly affected by von Willebrand’s disease are:
- Doberman Pinscher
- Shetland Sheepdog
- German wirehaired
- Scottish Terriers
- Dutch Kooiker
But, vWD can, in theory, be carried, transmitted, and expressed in any dog with any of the formerly mentioned breeds present in their ancestry, although there are dogs that are more at risk than others.
Increased Risk Factors Associated with vWD in Canines
The most significant risk associated with vWD is the risk of excessive blood loss. As some medications are known to decrease platelet function further, your vet should avoid these as they can increase the risk of spontaneous bleeding in patients. Some of these drugs include:
If you know your dog suffers from vWD, you must inform your veterinarian.
No one wants to see their dog sick, and even more, we do not want to see them bleed excessively! Luckily there are now tests available to screen for von Willebrand’s disease, and remember, even if your dog is a carrier, it does not mean it cannot live a long and healthy life!