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Comparative Coagulation


FAQ's on Hemophilia B in Deutsch Drahthaar

What is Hemophilia B?

Hemophilia B is an inherited bleeding disorder caused by specific deficiency of coagulation Factor IX (Factor 9). In addition to Deutsch Drahthaar, Hemophilia B has been identified in more than 25 different breeds and in mixed breed dogs.

What are the clinical signs of hemophilia?

Severely affected dogs have recurrent and potentially fatal bleeds into chest, abdomen, joints, or muscles. Hemophilia B in Deutsch Drahthaar, however is relatively mild. Affected dogs have shown signs of lameness and swollen joints after strenuous exercise, prolonged bleeding from minor wounds, and hemorrhagic complications after surgery. Although Hemophilia B impacts on quality of life and performance, virtually all affected dogs survive to adulthood.

What is the inheritance pattern of Hemophilia B?

Hemophilia B is a sex-linked, recessive trait. The Factor IX gene is carried on the X chromosome. All males (XY) have a single X chromosome, inherited from their dam. If that X chromosome carries a mutant gene, the male is affected with hemophilia. All females (XX) inherit one X-chromosome from dam and one from sire. If a female inherits a mutant gene, from either parent, she is a carrier of hemophilia. Carrier females appear clinically normal and do NOT express a bleeding tendency.

Hemophilia can be transmitted by an affected sire or carrier dam as follows:

Parents Offspring
Hemophilic male (XhY) x Clear female (XX) all carrier females (XhX) & all clear males (XY)
   
Clear male (XY) x Carrier female (XhX) 50% clear females (XX) & 50% carrier females (XhX)
50% clear males (XY) & 50% hemophilic males (XhY)

How is hemophilia diagnosed?

Affected dogs are accurately diagnosed by directly measuring blood levels of Factor IX. Severely affected dogs have less than 2% Factor IX. Hemophilic Drahthaars have values of approximately 5 to 15% Factor IX. Normal Factor IX is greater than 50%. Carrier females often have normal values of Factor IX.

What is the mutation detection test for Hemophilia B?

This direct DNA test defines the presence (or absence) of a specific mutation in the Factor IX gene. The test is performed by isolating DNA from a blood sample and then amplifying the region of the Factor IX gene that contains a mutation associated with Hemophilia B in Drahthaar. Carrier females have one normal Factor IX gene and one mutant gene. Clear females have two normal Factor IX genes.

What is the difference between a Factor IX assay and the mutation detection test?

Factor IX assay:

  • A specific measure of the blood protein, coagulation Factor IX. The test must be performed on blood drawn in citrate anticoagulant and processed to separate plasma. Factor IX analysis is the definitive test for diagnosing Hemophilia B. Affected dogs have Factor IX values below 20%.

Mutation test:

  • An analysis of a specific region of the Factor IX gene known to contain a mutation in Hemophilia B-affected and carrier Deutsch Drahthaar. The Hemophilia B mutation detection test is NOT a parentage test and will NOT define a dog's status for von Willebrand's disease.

Which dogs should be evaluated with the mutation detection test?

Females:

  • The DNA test for mutation detection is the only accurate Hemophilia B carrier detection test for individual females in use or under consideration for breeding. Carrier females often have normal Factor IX values.

Males:

  • Blood samples for Factor IX assay should be drawn in citrate anticoagulant and centrifuged to separate plasma from cells. The mutation detection test requires submission of 3.0 mL EDTA blood.

How do I submit samples for Hemophilia B screening?

Females:

  • The mutation detection test requires submission of 3.0-mL whole blood in EDTA anticoagulant (purple top tube).

Males:

  • A male's status can be directly defined with a Factor IX assay, however the mutation detection test will accurately differentiate affected from clear males if Factor IX assays are not performed.

Detailed sampling instructions are available from the Comparative Coagulation Section (607-275-0622; Sample submission webpage).

What are the costs and test turnaround times for Hemophilia B screening?

Mutation detection test:

  • The cost for the mutation detection (DNA) test is $100.00 per sample. The analyses will be performed biweekly (every other week) with results reported out within 1 to 2 weeks of sample receipt.

Factor IX assay:

  • The cost for coagulation Factor IX analysis alone is $12.00. The Factor IX assay is performed daily, with results reported out within 24 hours of sample receipt.

Where can I learn more about canine Hemophilia B?

Please call the Comparative Coagulation Section laboratory at 607-275-0622 for information on testing, or any other questions on bleeding disorders. Additional information is available in the following journal articles:

  • Dodds WJ, Moynihan AC, Fisher TM, and Trauner DB. 1981. The frequencies of inherited blood and eye diseases as determined by genetic screening programs. J Am Anim Hosp Assoc, 17:697-704.
  • Brooks M. Hereditary Bleeding Disorders in Dogs and Cats. Veterinary Medicine June 1999; 94:555-564.
  • Brooks M and Sargan D. Genetic Aspects of Disease in Dogs. In: Sampson J. and Ruvinsky, A. (eds). The Genetics of the Dog. Wallingford, UK, CABI Publishing, 2001;191-266.
  • Brooks MB, Gu W, Barnas JL, Ray J, Ray K. A Line 1 insertion in the factor IX gene segregates with mild hemophilia B in dogs. Mammalian Genome 2003;14:788-795.