Von Willebrand's disease is a bleeding disorder caused by a defect in a blood protein required for normal clotting and control of hemorrhage. This disease occurs with varying frequency in many different breeds of dog (including the Drahthaar), as well as other domestic animals and human beings.
In the same manner as for hip dysplasia, Verein Deutsch Drahthaar (VDD/GNA) has instituted a "voluntary" testing program. The purpose being: to identify and track affected individuals and to assist Cornell University's Comparative Hematology Section in developing a database to help better understand the genetic behavior of the disease.
Cause...The bleeding tendency of vWD is caused by a deficiency of von Willebrand factor protein (vWF). This blood protein is involved in the first phase of blood vessel repair, and is distinct from coagulation factors.
Inheritance...The gene for vWF is carried on an autosome and both males and females have two genes for this protein, one inherited from dam and one from sire.
Expression and Transmission...In most breeds, the presence of one abnormal gene is sufficient to cause a bleeding tendency in some individuals. This inheritance pattern is called autosomal incompletely dominant. In a few breeds (Scottish terrier, German wirehair, and Chesapeake retriever) individuals with one normal and one abnormal gene are asymptomatic carriers and all affected individuals have two abnormal genes. This pattern is autosomal recessive.
Males and females with one abnormal gene are carriers of the vWD trait and on average they will transmit the abnormal gene to one-half of their offspring. Carriers may be completely asymptomatic, or in most breeds, carriers may also have mild to severe bleeding tendency.
Males and females with two abnormal genes are invariably affected with vWD and in many breeds bleeding is so severe that pups die in utero or soon after birth. If these individuals survive to breed, they transmit and abnormal gene to all of their offspring.
Signs...Severity of bleeding is highly variable in dogs affected with vWD. In general, spontaneous bleeding tends to occur from mucous membranes lining the nose, mouth, urinary, reproductive, and intestinal tracts. Excessive bleeding in puppies may be noted after tail docking, cropping, dewclaw removal or tooth eruption. IN some dogs, abnormal bleeding is only seen after surgery or trauma. Concurrent stress conditions such as viral and bacterial infections, hormonal fluctuations associated with heat cycles or pregnancy, and endocrine disorders causing deficiencies of steroid or thyroid hormone can all exacerbate signs of hemorrhage in dogs affected with vWD.
Laboratory Diagnosis...Specific assays of canine von Willebrand's factor are needed to diagnose vWD in dogs. The most widely used test is the von Willebrands factor antigen (vWF:Ag) test. The amount of vWF in a test plasma sample is measured and then reported as vWF:Ag% compared to a standard control plasma. Measurement of plasma vWF:Ag% is used as a predictor of a dog's genetic status for the vWD trait. The following ranges for plasma vWF:Ag% have been established at the Comparative Hematology section:NORMAL RANGE 70 - 180% vWF:Ag%
Dogs testing in the normal range are considered clear of the vWD trait, and at low risk for expressing or transmitting the vWD trait.
Dogs testing in the borderline range can not be accurately classified as carrier or clear of the trait on the basis of that measurement. This is an overlap region plasma vWF:Ag%, where some individuals are clear and some carriers of vWD.
Dogs testing in the abnormal range are considered carriers of the vWD trait, and are at risk for transmitting an abnormal vWF gene to their offspring, and in some individuals for expressing an abnormal bleeding tendency. The vWF:Ag%, alone, can not differentiate asymptomatic carriers from "bleeders" in most breeds.
Canine breeds most commonly affected...Von Willebrand's disease is the most common inherited bleeding disorder in dogs and has been described in over 50 breeds. The trait is most widespread in Doberman pincher, Pembroke Welsh Corgi, Scottish terrier, Shetland sheepdog and Golden retriever; however, certain lines or families within many breeds have a high proportion of carriers of the vWD trait. There are differences between the breeds in the proportion of carriers that actually express the trait by showing the abnormal or excessive hemorrhage.
Excerpt from Deutsch Drahthaar handout 1992
Marjory Brooks, DVM Dip. ACVIM
Comparative Hematology Section
Diagnostic Lab-Cornell U