Within the body is a biochemical pathway known as the clotting cascade. Whenever any tissue is injured the clotting cascade swings into action and prevents uncontrolled bleeding. This can be after bruising, cuts, trauma and any other tissue injury however minor. Each step is controlled by a different chemical reaction and or interaction and for these to work all the chemicals or interactions must be produced by the body-this is under genetic control. If any of the genes, which control the production of the steps, are missing or defective the individual may have clotting problems. Thus a minor bruise or knock results in bleeding into the tissue and wounds may bleed for longer than normal.
Factor VII is one of the proteins involved in the clotting cascade and is found in the early stages. If a blood vessel wall is injured Factor VII may leak out and bind with Tissue Factor, which is found, stuck to the outside wall of the blood vessels. This binding triggers a series of chemical reactions leading to a clot forming and the leak plugged.
Deficiency of Factor VII can lead to mild to moderate bleeding, as the cascade doesn’t progress properly. This deficiency is found in man as well as dogs and is inherited as a recessive disorder. Breeds known to be affected by this particular gene mutation are the Beagle, Deerhound, Airedale, Alaskan Klee Kai and Giant Schnauzer. There may be others as well.
A recessive disorder means that a dog needs to carry two copies of the mutant gene to be affected and have problems. The gene responsible for Factor VII deficiency was first properly identified in beagles in a research colony in the USA although it was known to be around before then. It has subsequently been found that the general beagle population around the world also carries this mutation and there are reports of beagles with bleeding disorders when they undergo surgery. It seems likely this gene is widespread as it often only produces a mild increase in clotting time, which goes unnoticed. So far several beagles around the world have been tested and the results support this. The gene test can be used to alert dog breeders to the status of their breeding stock and as a further tool to ensure they breed healthy dogs.
Factor VII is Vitamin K dependent and ingestion of anticoagulants such as warfarin reduces the liver’s ability to produce vitamin K. Warfarin and similar compounds are also the basis of many rat bait poisons. Many people will know of the risk of rat bait to dogs and how they can haemorrhage. A dog affected with Factor VII deficiency would be at high risk if it had ingested such a poison.
Unlike dogs with MLS, affected dogs should not be eliminated from the general population without careful consideration. Many affected dogs do not have severe bleeding problems and can be safely mated to a clear dog without producing affected puppies. When breeding the Beagle one must take lots of things into account. We are in a world now where DNA testing is advancing fast and this is another tool for breeders to use.
Diseases such as Steroid Responsive Meningitis, Epilepsy, Musladin-Lueke Syndrome and Hip Dysplasia are all currently discussed in the breed and we need to look at all aspects when breeding not just take a single test result and use it for our selection process.