Von Willebrand Disease (vWD) is an inherited bleeding disorder resulting from a lack or reduced level of a normal blood clotting protein called von Willebrand factor (vWF). vWD is the most common blood clotting disorder in dogs although rare in English Toy Terriers, and it is distinct from Haemophilia.
- Symptoms of Von Willebrand’s Disease
- Diagnosis & Treatment
- Genetic Inheritance of Von Willebrand’s Disease
- DNA Testing for Von Willebrand’s Disease
Symptoms of Von Willebrand Disease
Symptoms of Von Willebrand Disease include excessive bleeding after an injury, trauma or a surgery, as well as spontaneous bleeding from the nose, gum and other mucous membranes.
Often dogs don’t show clinical signs until something starts the bleeding, such as nail trimming, teething, spaying, sterilizing, tail docking, cropping or other causes. Bleeding can also occur internally in the stomach, intestines, urinary tracts, the genitals and / or into the joints.
You must seek veterinary advice if your dog is affected by excessive or sudden bleeding.
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Diagnosis & Treatment
A qualified vet can diagnose Von Willebrand Disease and may use a variety of diagnostic tools including blood tests to measure the amount of Von Willebrand factor antigen assay, buccal mucosal bleeding time (BMBT) tests which measures the time it takes for a blood clot to form as well as DNA Tests for the vWD gene.
There is no cure for von Willebrand disease in dogs, but it can be managed. Treatments include blood transfusions, DDAVP, and limiting certain medications.
Owners of dogs affected by vWD will also need to manage their dogs by e.g. limiting rough play, making all vets treating the dog for any condition that the dog is affected by vWD, etc.
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Genetic Inheritance of Von Willebrand Disease
Von Willebrand Disease is an autosomal-recessive condition. This means that a dog must inherit two copies of an abnormal gene (one from its mother and one from its father) before its health is affected. A dog that inherits only one copy of the abnormal gene (from its mother or its father) will have no signs of vWD but will be a carrier and may pass the gene on to any offspring.
English Toy Terriers are affected by Type I von Willebrand’s disease which is considered relatively mild, and it is rare in English Toy Terriers. We recommend that all breeders ensure that both sire and dam are tested to inform future mating decisions to avoid producing puppies that are affected by vWD.
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DNA Testing for Von Willebrand Disease
DNA testing is available to identify whether a dog is a carrier of Von Willebrand Disease. This test screens for a specific DNA mutation in the VWF gene that causes a deficiency in von Willebrand factor, a protein necessary for normal platelet function. The mutation is inherited in an autosomal recessive manner. Typically, the test requires a straightforward swab taken from inside the cheek.
Test kits can be ordered through:
Both of these testing providers can also test for Juvenile Dilated Cardiomyopathy (JDCM) and Xanthinuria. We recommend that all breeders carry out DNA tests for JCDM and Xanthinuria on potential sires and dams, as well as having Patella Luxation Tests as a minimum.
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Interpreting Test Results
- ‘D’ indicate the deleterious (HUU) form of the gene.
- ‘N’ indicates the normal form of the gene.
A dog’s particular combination of N or D forms of the gene is known as its genotype.
Clear (N/N):
Clear dogs have no copies of the mutation and cannot pass the mutation on to offspring. However, this test result does not rule out the possibility that a dog could be affected or a carrier for a different mutation that results in urinary stones.
Carrier (D/N):
A carrier dog has only one copy of the mutation. Carriers are not considered to be at significant risk for bleeding. Carriers will, on average, pass the mutation on to half of their offspring. This does not mean that they need to be taken out of the breeding pool, but they should be bred to clear dogs to avoid producing affected puppies.
Affected (D/D):
An affected dog has two copies of the mutation (this is also referred to as being homozygous affected) and has von Willebrand disease and resultant increased risk for bleeding. Affected dogs will pass on a copy of the mutation to all of their offspring, but if bred to clear dogs, the offspring will only be carriers. Dogs with von Willebrand disease are at risk for bleeding from mucosal surfaces, such as the gums, nose, bladder or intestinal tract lining, and are at risk for excessive bleeding after surgical procedures.
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Breeding Outcomes
Carriers of Von Willebrand Disease should not be bred to other carriers and mated only to partners who have tested clear of vWD. It is essential that breeders test for vWD to inform their breeding decisions to avoid producing vWD affected dogs.
- Clear (N/N) x Clear (N/N) = 100% Clear (N/N)
- Clear (N/N) x Carrier (D/N) = 50% Clear (N/N), 50% Carrier (D/N)
(This is an average, individual litters may see anywhere from 100% Clear to 100% Carrier) - Clear (N/N) x Affected (D/D) = 100% Carrier (D/N)
- Carrier (D/N) x Carrier (D/N) = 25% Clear (N/N), 50% Carrier (D/N), 25% Affected (D/D)
(This is an average, individual litters may see more or less of any result) - Carrier (D/N) x Affected (D/D) = 50% Carrier (D/N), 50% Affected (D/D)
(This is an average, individual litters may see anywhere from 100% Carrier to 100% Affected) - Affected (D/D) x Affected (D/D) = 100% Affected (D/D)
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Submission of Von Willebrand Test Results
DNA testing for von Willebrand is not one of the ETT Club or the Kennel Club’s recommended mandatory tests for the English Toy Terrier (B&T), however, the test is still valuable and we encourage all breeders to have their dogs tested if used for breeding.
There is no central point to record the test results for von Willebrand. The ETT Club therefore advise these results are filed with your dog’s registration papers.
The ETT Club may ask for information regarding these tests in future health surveys.
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