von Willebrand Disease Type 2 DNA Test
Although von Willebrands Disease Type 2 (vWD2) DNA Tests are optional, SCOA Health recommends breeders take advantage of all health screening tests available to them to ensure the maximum amount of accessible health information.
It is acceptable to skip 1 generation and claim “clear by parentage”(CBP) for only those offspring when BOTH sire and dam have been tested with “clear” results. Using CBP labels can apply to direct DNA mutation tests for which they are 100% accurate. vWD2 is a direct mutation test.
Von Willebrands Disease is an inherited bleeding disorder. It is similar to hemophilia in people. vWD Inheritance
There are 3 different types of vWD, type 1, type 2 and type 3. Types 1 and 3 are “quantitative” abnormalities. These dogs contain low to no vWD clotting ability. They lack the amount of vWD factor necessary to stop bleeding. Type 1 is a more mild common form and Type 3 is a severe form. von Willebrands Disease
Type 2 is quite different from type 1 and 3 in that it is a “qualitative” abnormality. This means that the dog produces the correct amount of vWD clotting factor but the plasma protein is physically defective and unable to function properly and clot. The blood may contain only a few defective proteins or many defective proteins. This then results in a range of clinical significance from a mild form of Type 2 or a severe form of Type 2. Due to the lack of clarity regarding the clinical impact of receiving an “affected” or “at risk” DNA test result, further functional plasma protein blood tests called vWD factor antigen assay (vWF:Ag) are necessary to categorize the clinical severity of the disease.
vWD2 Factor Antigen Assay Test
von Willebrands Type 2 DNA tests can be done on dogs of any age and there are many reputable labs that perform this DNA test.
vWD2 DNA tests are a very easy test that is done by a simple buccal (cheek) swab that picks up cheek cells containing your dog’s DNA.
It is a DNA test that will indicate results of “Clear”, “Carrier” or “Affected/At Risk”.
A dog with “Clear” results has 2 normal genes. A dog with “Carrier” results has 1 normal gene and 1 mutated gene and does not exhibit signs of the disease. A dog with “Affected/At Risk” results carries 2 mutated genes can exhibit varying signs of the disease from mild to severe.
Through diligent DNA testing, carriers can be managed in a breeding program, as they are necessary in preserving and expanding our breed’s gene pool.
Breeding strategies when planning for dogs with “Carrier” status is they MUST ONLY be bred to a dog with “Clear” status, which will result in a theoretical litter of 50% “clear” puppies and 50% “carrier” puppies. Any offspring from this combination of mating used for subsequent breeding, MUST be vWD type 2 DNA tested.
Autosomal Recessive Mode of Inheritance
Graphics Courtesy of Andrea Bolldorf
MODE OF INHERITANCE GRAPHIC