Breeds Affected: Thoroughbred, Oldenburg Horse, Quarter Horse, Peruvian Paso, possibly others

Samples Accepted: Blood, Hair

Disease Information
: Glanzmann’s Thrombasthenia (GT) is a platelet defect.  The blood does not clot normally, and the most common symptom in affected horses s recurrent nosebleeds (epistaxis).

Inheritance Information: Glanzmann’s Thrombasthenia (GT) is autosomal recessive, meaning that animals with two copies of this allele will be affected. Animals with one copy of the gene will be clinically-normal carriers. There are two different mutations that cause the disease in the horse, and it is possible for horses to have both.  This test detects both mutations.

The possible genotypes are:
N/N The horse is normal, and cannot produce GT-affected offspring.

N/gt1 The horse is a carrier of GT, and can pass the allele on to approximately 50% of any offspring. If bred to another N/gt1 carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.

N/gt2 The horse is a carrier of GT, and can pass the allele on to approximately 50% of any offspring. If bred to another N/gt2 carrier, approximately 25% of the offspring will be normal, 50% will be carriers, and 25% will be affected.

gt1/gt1 The horse is affected with GT. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/gt1 carrier, 50% of the offspring will be carriers and 50% will be affected.

gt2/gt2 The horse is affected with GT. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/gt2 carrier, 50% of the offspring will be carriers and 50% will be affected.

gt1/gt2 The horse is affected with GT. If bred to a normal animal, 100% of the offspring will be carriers. If bred to a N/gt1 or N/gt2 carrier, 50% of the offspring will be carriers and 50% will be affected.

Recommendations:
– Carriers may be bred to normal animals (N/gt1/gt2 x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
– Breeding two carriers (N/gt1/gt2 x N/gt1/gt2) is not recommended due to the possibility of 25% of the offspring being affected.


Test Information gt1
: This test is based on a single base change in the ITGA2B gene, identified in the Thoroughbred, Oldenbourg, and Quarter Horse.

Test Information gt2: This test is based on a 10 base deletion in the ITGA2B gene, identified in the Peruvian Paso and Quarter Horse.

Sanz, MG., Wills, TB., Christopherson, P., Hines, MT.: Glanzmann thrombasthenia in a 17-year-old Peruvian Paso mare. Vet Clin Pathol 40:48-51, 2011. Pubmed reference: 21291483. DOI: 10.1111/j.1939-165X.2011.00289.x.

Christopherson, PW., van Santen, VL., Livesey, L., Boudreaux, MK.: A 10-base-pair deletion in the gene encoding platelet glycoprotein IIb associated with Glanzmann thrombasthenia in a horse. J Vet Intern Med 21:196-8, 2007. Pubmed reference: 17338169.

Macieira, S., Rivard, G.E., Champagne, J., Lavoie, J.P., Bédard, C.: Glanzmann thrombasthenia in an Oldenbourg filly. Vet Clin Pathol 36:204-8, 2007. Pubmed reference: 17523098.

Christopherson, PW., Insalaco, TA., van Santen, VL., Livesey, L., Bourne, C., Boudreaux, MK.: Characterization of the cDNA Encoding alphaIIb and beta3 in normal horses and two horses with Glanzmann thrombasthenia. Vet Pathol 43:78-82, 2006. Pubmed reference: 16407493. DOI: 10.1354/vp.43-1-78.

Further information is available at the Online Mendelian Inheritance in Animals website.

Test #: H115
Cost: 60 € (excl. VAT)
Time: 7-10 days