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von Willebrand's disease (vWD)

This is the most common inherited bleeding disorder in dogs. It causes defective blood clotting due to reduced amounts of von Willebrand's factor (vWF) - a protein which helps tiny blood cells called platelets to adhere to each other and form an effective blood clot in the body.

Many breeds may be genetic carriers of this trait, but problems are most likely to be seen in Doberman Pinschers, German Shepherd dogs and Labrador Retrievers. Both sexes are affected equally.

Your questions answered

What problems are caused?

Affected dogs can have poor blood clotting, making them prone to bruising and bleeding. This can be serious and dangerous if these dogs have to undergo major surgery for any reason, or if they are badly injured. Extensive and continued bleeding can occur from even small blood vessels, complicating anaesthesia and surgery. Protracted bleeding may also occur during 'normal' events such as oestrus and giving birth in female dogs. Seriously affected puppies are likely to die.
 
As dogs get older, they may be less likely to bleed excessively. However, the presence of another disease (often the case in patients receiving surgery) can make the underlying bleeding tendency worse.

In some dogs the symptoms are so mild that no clinical problems are caused.

Can vWD be detected in affected dogs?

Yes, if they are tested. Some routine measurements of blood clotting are normal in dogs with vWD, eg they have normal numbers of platelets in their blood and normal amounts of the other proteins involved in blood clotting.

A simple screening test known as the Buccal Mucosa Bleeding Time (BMBT) is used to check for effective blood clotting. If this test is prolonged or suspicious, ie if a stable blood clot is not forming, a measurement of von Willebrand's factor in the plasma is made. Affected dogs will have abnormally low levels of vWF or perhaps abnormalities in the molecular composition of the vWF.

Testing is generally only done where there is suspicion of disease or in dogs facing major surgery. If you have any suspicions that your dog's bleeding time is abnormal then testing would be sensible. Continued bleeding for hours after minor injuries, eg a torn nail, superficial skin wounds, loss of a tooth, all point towards a possible blood clotting problem. In normal dogs bleeding should stop after 10-20 minutes.

What happens if it is only suspected once bleeding has started?

Dogs which are already bleeding can be treated with plasma or blood transfusions from healthy dogs. The healthy plasma contains vWF which the body can then use to assist blood clotting. Cryoprecipitate is a concentrated form of vWF and is ideal but not always available. Drug treatment using a substance known as vasopressin is also possible though this drug may not always be kept in many general practices.

If these treatments are not possible or available, intravenous drips are given to replace fluid losses in blood together with surgical or other measures to stop bleeding.

Should affected dogs be bred from?

No, in an attempt to limit occurrence of this disease breeding should not occur. Screening of potential breeding animals should be carried out beforehand, if possible, in an attempt to pick up animals not showing any symptoms, but carrying the disease. This is relevant in Dobermans particularly, since this is the breed most commonly associated with the disease.

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