This disease consists of a tendency to uncontrollable bleeding at the slightest trauma. It is a sex-linked inherited deficiency of the blood clotting Factor 8 (F V111). This is an essential co-factor in the intrinsic pathway of coagulation, and deficiencies of less than 20% of normal blood will give rise to a bleeding tendency. The FV111 gene lies on the X chromosome and any male with a defective X chromosome will be affected by the condition.
Interestingly, the condition of Haemophilia 'A' in GSDs follows exactly the same mode of inheritance as it does in humans, and it is well worth remembering that from the figures available, one third of humans born in the U.K. suffering from this condition have NO previous family history of the disease.
The clinical expression of the disease can be divided into 3 categories: severe, FV111 of less than 1%; moderate, FV111 of 1-10%; mild, FV111 of 11-20%.
Severe haemophiliacs suffer from spontaneous haemorrhage and rarely reach adult life. All the German Shepherd Dogs, to date, have been up to 2 year old at the date of diagnosis, and have had a FV111 of 11-20%. Bilateral intermittent lameness with swollen painful joints due to haemarthroses precede chronic lameness. Invariably the bruising and bleeding episodes have been associated with trauma. Major injury, dental extraction, surgical trauma and fighting are life threatening and often fatal. It is almost impossible to control these major bleeds as it is necessary to raise the FV111 levels in the dog's blood plasma to 40-50% in order to arrest bleeding. The quantities of whole blood or plasma required to achieve this would cause circulatory overload. Thus the only effective means of managing this problem in the German Shepherd Dog is to remove affected males and carrier females from the breeding program.
If an affected male is allowed to be used for breeding purposes, all of his female progeny will carry the defective X chromosome necessary to perpetuate the disease. They in turn will pass the disease on to half of all of their offspring. On average, half of the sons of affected females suffer from the disease and half of the daughters will be carriers. It is a chain reaction which can quickly become out of control.
It is possible to screen for this condition in pups of 5 weeks old. Diagnosing this condition is a relatively simple procedure in the male as he either has either normal or abnormal FV111 levels in his blood stream. Therefore if breeders screen all males prior to sale, they can be secure in the knowledge that they are selling puppies who do not pose a threat to future generations, and that they have sold a dog who is not going to bleed to death at the first encounter with trauma.
The blood status of male offspring provides useful information in relation to the status of the bitch producing them. Testing of females for non carrier status directly is less accurate. It is possible that FV111 levels of carrier females may be quite normal or only slightly reduced. This is possible because the females carry 2 X chromosomes. At random only one is expressed in each cell, thus an affected female may herself have normal clotting levels -- all carrier bitches, to date, have tested less than 60% -- and testing will only result in an estimate of probability regarding their carrier status.
All confirmed published data on German Shepherd Dogs suffering from haemophilia in the European countries can be traced back to one dog: Canto von der Wienerau. It has long been accepted that this dog was himself a haemophiliac, and was well used at stud. All his daughters were carriers and half of their offspring would be affected males or carrier females. Screening of animals with Canto in their female lines is therefore advisable. To further compound the issue, several affected males found their way into the breeding program prior to diagnosis, and all their daughters will have been carriers.
Published data is not, however, the only data, and other new mutations within the GSD breed have been diagnosed as it is in their human counterparts, with no previous family history. Sadly, details of this data are not publically available. It is therefore all the more advisable to screen all animals, but in particular the males, if there is to be any hope of preventing perpetuation of this condition.
Copyright 1997 Alyson Lockwood. No reproduction of any kind without the permission of the author.