C114 - Canine Hemophilia B

Hemophilia B is a X-linked bleeding disorder caused by a deficiency of functional coagulation factor IX (Factor IX). Normally, the body responds to an injury that causes bleeding through a complex defense system. This consists of local changes in the damaged blood vessels, activation of blood platelet cells, and activation of the coagulation process. Since dogs suffering from Hemophilia B fail to produce the Factor IX, blood clotting in these animals is severely affected. The clinical signs associated with Hemophilia B vary widely, based on the severity of the bleeding disorder and where in the body the bleeding occurs. Affected dogs typically display symptoms such as bloody diarrhea that is difficult to control, areas of bleeding under the skin, or lameness (due to bleeding into muscles or joints). Bleeding under the skin or into the muscle may occur after routine vaccination, or there may be prolonged or severe bleeding at surgery. Other less common problems include respiratory difficulties due to bleeding into the chest or around airways, weakness, paralysis, or even sudden death due to bleeding into the brain or spinal cord.

Canine Hemophilia B is one of the few sex-linked traits observed in dogs (X-linked). Because males have only one X chromosome, a male dog is either affected or clear of the disease and cannot be an unaffected carrier. Females however, carry two X chromosomes and may be affected (abnormal gene on both X chromosomes), clear, or a carrier with no clinical signs (one gene affected). In effect, this disease is carried by females but affects mostly males.

Previously, laboratory diagnosis of Hemophilia B required detection and quantification of specific clotting factors associated with the disease. Specific clotting factors in affected animals are markedly lower than normal animals, allowing veterinarians to determine whether an animal is affected. Recently, a DNA based test for the detection of the specific gene responsible for Hemophilia B became available. Since this DNA test detects the presence of the actual gene involved in Hemophilia B, rather than the products of the gene (Factor IX), the accuracy rate is 100%. This test provides breeders and veterinarians with a diagnostic tool that can definitively diagnose Hemophilia B, therefore it can be seen whether a dog is affected or a carrier (female).