VONWILLEBRANDS-DISEASE IN SCOTTISH TERRIERS IN AUSTRALIA

Over a 5-year period (1988-92), von Willebrand factor antigen (vWf:Ag) assays were performed on plasma samples from 207 Scottish Terriers, B ased on these tests, 47 dogs (23%) had vWf:Ag concentrations < 50 cani ne units (CU)/dL and were classified as heterozygous carriers of the v on Willebrand's disease (vWD) gene, while 9 (4%) had concentrations be low the sensitivity of the assays and were classified as homozygous, T here was thus an overall prevalence of 27% for the vWD gene in the Sco ttish Terriers tested, The homozygous dogs (median age 0.6 years at di agnosis) consisted of 7 males and 2 females. Eight of these had haemor rhage attributable to the disease, mostly spontaneous and from the ora l mucosa, Other signs included haemorrhage induced by trauma or surger y, easy bruising and epistaxis, Many haemorrhagic episodes were severe enough to warrant therapeutic intervention and there was a single fat ality, Pedigree analysis, possible in 7 of the dogs, revealed that eac h was the progeny of a mating between dogs with vWf:Ag concentrations < 50 CU/dL, which supported an autosomal recessive mode of inheritance . A single heterozygous carrier suffered haemorrhage after surgery tha t, in contrast to the homozygotes, was mild and did not require therap y. The data indicate that vWD is a significant problem in Scottish Ter riers in Australia, Accordingly, we recommend that steps be taken to r educe the prevalence of the disease and thereby the number of clinical ly affected dogs, such as the establishment of a national testing sche me to determine the vWD status of all breeding dogs.