Robert H. Loechel1; Kathi Springer3; George J. Brewer1,2
Vetgen has been offering DNA based tests for Type I and Type III von Willebrand's disease (vWD) for more than ten years. During that time, the number of breeds for which a Type I test is available has increased to ten to include the Bernese Mountain Dog, Coton de Tulear, Doberman Pinscher, Drentsche Patrijschond, German Pinscher, Kerry Blue Terrier, Manchester Terrier, Papillion, Pembroke Welsh Corgi, and Poodle. The initial Type III mutation identified is still found only in Scottish Terriers and Shetland Sheepdogs. The purpose of this poster is to both educate the viewer as to the availability of genetic tests for vWD, and to show that these tests are an effective means of gradually eliminating unwanted alleles from a population. Specific focus will be on the allelic frequency of the vWD alleles in the first and last years of a ten-year period from 1997-2006 for the two breeds with Type III, and for two breeds with the milder Type I disease, Doberman Pinscher and Poodle. During this period the frequency of the Type III allele in Scottish Terriers and Shetland Sheepdogs dropped from approximately 4.5 % in each breed to approximately 3.5% and 2.5%, respectively. With respect to Type I vWD, the Doberman Pinscher is of particular interest because of the very high frequency of the mutant allele in this breed. The frequency dropped from approximately 50% in 1997 to just under 44% in 2006, with a 20% drop in the frequency of homozygous, or "affected" animals tested. The high frequency of this allele in the Doberman precludes most breeders from breeding away from it completely and thus creating a potential genetic bottleneck, or complete loss of their individual breeding program. Instead, it is common to continue breeding carriers, but only to clear dogs, thus the more gradual decline in allelic frequency. It must be pointed out that these data only represent the subset of each population which is subject to testing and while relevant to each of these breeds is not necessarily indicative of the frequency of the alleles in the entirety of each breed. Nevertheless, the data demonstrate that genetic testing for vWD alleles has been and will continue to be a useful tool in reducing the prevalence of the disease.