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Testing of dogs: VWD type III in Shetland Sheepdogs
Related tests
- Combination Shetland Sheepdog CEA + CNGA1-PRA + DM (SOD1A) + Gallbladder mucoceles + MDR1 + vWDIII + MH + BBS2
von Willebrand disease
Von Willebrand disease (vWD) is caused by plasmatic von Willebrand factor (vWF) insufficiency. VWF is a blood glycoprotein (not enzyme) important for blood coagulability.
Its primary function is to bind itself to other proteins (for example it stabilizes Factor VIII), and also facilitates aggregation and adhesion of the trombocytes to wound site. The deficiency or failure of vWF function causes bleeding which is most apparent in tissues having high blood flow shear in narrow vessels. VWD manifests oneself as a tendency to bleeding from skin and tissues. The disease can be inheritable or acquired.
In dogs (as well as in people), there were identified three types of vWD. Finally, there were identified five different mutations causing vWDs in dogs. Genetic tests have been already developed for all the mutations.
vWD type III
vWD type III is the most serious form of Von Willebrand disease, because the symptom is very massive life endangering bleeding. This form is typical by the fact that vWF totally absents in plasma. The illness is inherited as an autosomal recessive trait. Carriers have lower level of vWF in blood, but generally they have normal homeostasis. vWD type III occurs mainly with :
- Scottish terrier (Venta etal. 2000)
- Shetland sheep dog (Pathak et al.2004)
- Kooikerhondje (Rieger et al.1998)
VWD III is possible to determine by an immunological test. The determination is not so accurate, because the result can be affected by several factors - for example: way of blood taking and sample storage, pregnancy, vaccination, individual's age, hormones , etc... The dog can appears as immunologically health one day, and second day as an potential carrier. The testing is not suitable for standard practice.
The proper alternative is a genetic test, which clearly demonstrates, which individuals are healthy, which one are carries or affected of vWD. Test can be performed in any age from blood sample or from buccal swabs. Genetic examination is not affected by casual status of the dog, like the pregnancy or illness are.
vWD type III in Shetland Sheepdogs
Causal mutation of vWD III disease in Shetland Sheepdogs was identified as T deletion in exon 7 of vWF gene.
References:
Type 3 von Willebrand's disease in a Shetland sheepdog. Pathak EJ. Can Vet J. 2004 Aug; 45(8):685-7.
Rieger M, Schwarz HP, Turecek PL, Dorner F, van Mourik JA, Mannhalter C: Identification of mutations in the canine von Willebrand factor gene associated with type III von Willebrand disease; Thromb Haemost. 1998 Aug;80(2):332-7