Sheltie von Willebrand's Disease
Can Now Be Diagnosed by a DNA Test
by George J. Brewer, Professor, Department of Human Genetics and Internal Medicine, University of Michigan Medical School and Patrick J. Venta, Assistant Professor, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, Co-Founders of VetGen LLC
Von Willebrand's disease vWD, an inherited bleeding disorder, usually comes in two major types, type I and type III. (There is also a rarer Type II, not relevant to Shelties). Type III is a severe bleeding disorder with a high risk of spontaneous bleeding as well as a risk of serious bleeding from trauma and surgery. It is probably best known in Scottish Terriers. Type I is milder, with most of the risk coming from trauma or surgery. It is probably best known in Doberman Pinschers. The Sheltie breed has type III vWD, the severe type. There may also be a second less prevalent defect, causing some Shelties to have the less severe Type I vWD, but this is uncertain at present.
In the past, the problem in trying to breed out vWD is that identifying carriers of the gene has been a problem.(Carriers are dogs who have the defective gene on one chromosome but a normal gene on the other, don't bleed, but can pass the defective gene on to their puppies). The vWD test available in the past has been an assay of von Willebrand factor protein. It is fairly reliable in detecting affected animals, (those with two copies of the defective gene, and at risk for bleeding), because these animals usually have a very low level of the factor. But this test is very unreliable in differentiating gene carriers from clear animals. (Clear dogs are dogs with two copies of the normal gene). Further, many environmental factors influence the protein factor assay. Thus, a dog that tested in the "normal" range one year could have a low value in the "carrier" range the next year. As a result breeders have not had much success breeding out this disease. And it has been frustrating to breeders to go to the expense and trouble of doing "the right thing", testing for vWD, and find that their results were so unreliable.
Enter the era of DNA testing! DNA tests have now been developed for the type III vWD of Scotties, the type I vWD of Dobermans, and the type III vWD for Shelties. These DNA tests can be done at any age, can be done from mouth swabs collected by the breeder/owner (the swabs pick up cells from inside the mouth which provide the DNA), and unambiguously classify dogs for the rest of their lives into affected, carrier, and clear animals. With this test the breeder can rapidly eliminate the vWD disease gene from the breed. If a particularly valuable dog turns out to be a carrier, it can be bred to a clear animal, and non-carrier puppies saved for the next round of breeding.
The research teams who have accomplished the above work are scientists at the University of Michigan, Michigan State University, and at a commercial enterprise, VetGen. VetGen markets the DNA tests to breeders and veterinarians.
Questions have been raised from time-to-time as to whether vWD is a health problem in the Sheltie breed. We can say with scientific certainty that type III is a significant problem in Shelties. The mutation we have discovered has been found to be the causative mutation in several Shelties severely affected with bleeding from vWD. Further, VetGen has now done enough testing on Shelties to have a reasonably good estimate of the frequency of carriers. A little over 11% of Shelties are carriers of the type III vWD mutation. This is a significant health burden in Shelties and it would be good to get rid of this disease gene by using the DNA test. It should be emphasized that carriers will be clinically normal, and can be used as pets. As said above, if a carrier has excellent breed characteristics, it can be bred to a clear animal, and only clear animals among the progeny be used for further breeding.
It is possible that there may also be a mutation for type I vWD in Shelties. If it is present in Shelties, this type of vWD is a mild type, and poses much less risk for bleeding. We won't know for a little time whether or not type I is present in Shelties.
The mouth swabs and test information for vWD in Shelties can be obtained from VetGen (See the link below).
Canine: vWD Patents
US Patent No. 6,040,143 and 6,074,832
Licensed Exclusively by The Board of Regents of the
University of Michigan (Ann Arbor, MI) System to VetGen LLC