von Willerbrands Disease (Type 1)
von Willebrand disease (vWD) is probably the most common inherited bleeding disorder in dogs. It is caused by lack of von Willebrand factor which is a protein that plays a key role in the blood clotting process resulting in prolonged bleeding. The disorder occurs in varying degrees of severity ranging from trivial bleeding to excessive life threatening haemorrhages.
Symptoms can include spontaneous bleeding from the nose, gum and other mucous membranes. In affected dogs, excessive bleeding can occur after an injury, trauma or a surgery. 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. Type I von Willebrand's disease is considered relatively mild when compared to Type II in Scotch Terriers and Shetland Sheep Dogs and Type III in the German Wirehaired pointer, Type II and Type III are much more severe than type I.
vWD Type I is transmitted as autosomal incomplete dominant trait . This means that a dog that is genetically clear (also called homozygous normal) will not develop the vWD disorder and will not pass it to its offspring. Carrier dogs which carries one copy of the abnormal gene and another normal copy (also known as heterozygous) may have bleeding tendency. These carrier dogs will pass the abnormal gene to their offspring with a probability of 50%, the trait is called incomplete dominance because carrier dogs may not develop the disorder at all but they will still pass the abnormal gene to their offspring. Because it is very uncommon for carriers to show symptoms of vWD this condition is treated as Recessive. Affected dogs (carry two copies of the abnormal gene) will develop the vWD disorder and will pass the abnormal gene to each of their offspring.
Inheritance : AUTOSOMAL RECESSIVE trait
Genotype: N / N [ Homozygous normal ]
The dog is noncarrier of the mutant gene.
The dog will never develop von Willebrand disease Type I (vWD I) and therefore it can be bred to any other dog.
Genotype: N / vWD [ Heterozygous ]
The dog carries one copy of the mutant gene and one copy of the normal gene.
The dog is very unlikely to develop von Willebrand disease Type I (vWD I) and if it does it will be in a mild form. Since it carries the mutant gene, it can pass it on to its offspring with the probability of 50%.
Genotype: vWD / vWD [ Homozygous mutant ]
The dog carries two copies of the mutant gene and therefore it will pass the mutant gene to its entire offspring.
The dog may develop von Willebrand disease Type I (vWD I) and will pass the mutant gene to its entire offspring
Testing for vWD must be done using a DNA test (Blood or buccal swab) - DO NOT have your dog tested by blood sampling alone as this test will be carried out using an ELISA test which can give variable results and is unrelaible.
Laboklin are the only European laboratory licenced to DNA test for vWD. (http://www.laboklin.co.uk) Current price £ 88.00
The sire and/or dam of your puppy may have been certified "CBP" on their pedigree - this means "clear by parentage" which indicates that both of the parents have either been tested and certified clear by DNA or, are also resultant of a "CBP" litter. Two clear dogs mated can only produce 'clear' puppies and these puppies are eligible to have "CBP" annotated onto their pedigrees at the Kennel Club.
The mathematical probability for matings is as follows:
CLEAR mated to CLEAR - produces 100% CLEAR puppies
CLEAR mated to CARRIER - produces 50% CLEAR and 50% CARRIER puppies
CLEAR mated to AFFECTED - produces 100% CARRIER puppies
CARRIER mated to CLEAR - produces 50% CLEAR and 50% CARRIER puppies
CARRIER mated to CARRIER - produces 25% CLEAR, 50% CARRIER and 25% AFFECTED puppies
CARRIER mated to AFFECTED - produces 50% CARRIER and 50% AFFECTED puppies
AFFECTED mated to CLEAR - produces 100% CARRIER puppies
AFFECTED mated to CARRIER - produces 25% CARRIER and 75% AFFECTED puppies
AFFECTED mated to AFFECTED - produces 100% AFFECTED puppies
We should never knowingly breed to produce affected puppies.