vWD

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Von Willebrand Disease (vWD)

Dobermanns may suffer from the mildest type of vWD - Type 1.

The blood-clotting disorder Von Willebrand Disease (vWD) was first identified in humans in the 1920s by Finnish doctor Dr. E. A. von Willebrand. It is a haemophilia-like disease, typified by the reduced quantity or absence of a certain clotting factor – the von Willebrand factor (vWf) - in the plasma. The factor is a glycoprotein and is necessary for the normal platelet function of blood clotting. Platelets are components of blood that assist with clotting; vWD does not lower the amount of platelets, but does change their constitution. Research has shown that 12 blood clotting ‘factors’ exist - vWD affects levels of Factor VIII.

vWD is unlikely to cause death, with most forms of the disease mild or in many cases difficult to detect. However, in some cases and particular breeds (eg. Scottish Terriers) Type III vWD cases can be life threatening or severe.

There are two forms of vWD – Inherited and Acquired. Inherited vWD (autosomal recessive) is the most common form of vWD in dogs and is divided into three types:

Type I:	Probably the most common as it is found in most breeds of dogs and inherited as an autosomal dominant trait. Bleeding disorders are due to reduced levels of vWf and is less severe than the other two types.
Type II:	Low concentration of abnormal vWf. Also inherited as a dominant trait and is the rarest of the three.
Type III:	The complete absence of vWf in affected dogs, thus the most severe of the three. Inherited as an autosomal recessive trait. Any episodes of bleeding usually require transfusions of blood or supply of the missing vWf.

A Direct Marker (gene) Test allows an accurate assessment of the disease and is 100% accurate. Unlike the Indirect Marker Test, the direct test does not require pedigree information as it can be used to diagnose an individual dog. Research has shown that carrier or affected dogs can show variable levels of vWf expression, therefore some affected dogs may bleed severely while other affected dogs may show very little or no bleeding.

It should be noted that vWD is not a death sentence for dogs, in fact many dogs with the disease can live quite normal lives and show no complications e.g. carriers of the recessive form who do not have the disease - Affected who do not have bleeding episodes. With careful mating strategies and genetic screening, the breeder can begin to bring the percentage of carriers or affected in their pedigree down and make an impact on the levels seen in breeds. But sensible breeders will not totally disregard quality dogs with an Affected result and lessen an already small gene pool. Again it should be stressed that vWD is not a death sentence for dogs.

The three readings for vWD are:

Clear	– no presence of the disease gene and cannot pass on any disease gene.
Carrier	– one copy of the disease gene is present, however the animal does not exhibit any symptoms of the disease. Therefore no medical problems arise. Carriers will pass on the disease gene to 50% of their offspring.
Affected	– two copies of the disease gene are present. The animal will always pass on the disease gene (mutation) to its offspring.

Mating results - Blue indicates Male - Red indicates Female

	Clear	Carrier	Affected
Clear	All Clear
Carrier	50%Clear, 50%Carrier	25% Clear, 50% Carrier, 25% Affected
Affected	All Carrier	50% Carrier, 50% Affected	All Affected

I personally mated an Affected Bitch to a Carrier Dog, 5 puppies were born and 4 (80%) were Carriers and 1 (20%) were Affected. This Affected bitch had a Caesarean Section to deliver this litter without incident and 3 months later was desexed, again without incident. Her Affected son was also neutered at 8 months of age without incident.

We have just done a Clear to Carrier mating with all 3 resulting puppies being vWD Clear.

I know of breeders who did Carrier to Carrier and did not get any Affected puppies. In fact the majority of the litter were Clears.

No sensible breeder would knowingly do an Affected to Affected mating.

This DNA test has only been available for the past 8 years or so (not quite 2 years in Australia) and prior to the test being available we did not see dogs bleeding to death. (except due to mostly Veterinarian incompetence/inexperience).

Clotting times are, however, the important issue. Affected dogs can, and quite often do, clot just as quickly as a Clear dog. If you are in doubt, and your dog requires surgery, ask your Veterinarian to carry out a simple clotting time test.

It should be pointed out that careful breeding can result in eradicating the gene in 2 - 3 generations. Again, sensible breeders will not totally disregard quality Affected Dogs or Bitches and cull them from their breeding programmes and lessen an already small gene pool. Again it should be stressed that vWD is not a death sentence for dogs.

DNA Testing is the ONLY definitive way of obtaining a correct result. This is done with a simple buccal swab. The Australian company now doing this testing usually have the results back to the owner of the dog within 5 working days, if not sooner, after receiving the swabs.

You can read more about DNA vWD testing and how to obtain testing kits at Genetic Science Services.

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