VON WILLEBRANDS DISEASE IN DOBERMANN DOGS IN AUSTRALIA

Over a 5-year period (1988-92), von Willebrand factor antigen (vWf:Ag) concentrations were determined on plasma samples from 614 Dobermanns. The vWf:Ag concentration was < 50 canine units (CU)/dL in 373 dogs (6 1%); these dogs were classified as carriers of the von Willebrand's di sease (vWD) gene. In order to identify which dogs were at risk of haem orrhage due to vWD, we determined a cut-off vWf:Ag concentration below which dogs could be considered at risk. This cut-off was chosen in or der to minimise the number of dogs genuinely at risk of haemorrhage, b eing wrongly classified as not at risk. This was done without sacrific ing the specificity of the cut-off to any great extent. A vWf:Ag conce ntration of < 36 CU/dL was empirically chosen as the optimum cut-off c oncentration. In 282 dogs (76% of the carriers), the vWf:Ag concentrat ion was below this cut-off and these dogs were, thus, classified as be ing at risk of haemorrhage due to vWD. Haemorrhage attributable to vWD was seen in 107 dogs (29% of the carriers, or 17% of all the dogs). H aemorrhage mostly followed trauma or surgery, but spontaneous genitour inary and gastrointestinal haemorrhages were also frequent. Of these d ogs, 92 were of known age, with a median of 3 years, and 102 were of k nown sex, with 61% being female. In 89 dogs in which the severity of h aemorrhage was subjectively assessed, mild and moderate bleeding occur red with similar frequency (48% and 43%, respectively). There were 8 c ases of severe haemorrhage, with two deaths. The likelihood of haemorr hage was related to the vWf:Ag concentration: only 8% of 91 dogs with concentrations between 36 and 49 CU/dL had haemorrhage attributable to vWD, but 36% with concentrations < 36 CU/dL did so. Furthermore, dogs with haemorrhage attributable to vWD had significantly (P < 0.001) lo wer vWf:Ag concentrations (median 12 CU/dL, n = 107) than dogs with no such history (median 30 CU/dL, n = 132). The data indicate that vWD i s a significant problem in the Dobermann breed in Australia and we acc ordingly recommend that steps be taken to reduce its prevalence, such as the establishment of a national testing scheme to determine the vWD status of all dogs used for breeding.