TYPE-III VON-WILLEBRANDS-DISEASE IN DUTCH KOOIKER DOGS

Type III von Willebrand's disease (vWD) was diagnosed in 38 Dutch kooi ker dogs. Ten male and 9 female probands had been referred independent ly of each other to the Utrecht University Clinic for Companion Animal s because of a moderate to severe bleeding tendency. Screening of 717 Dutch kooiker dogs, including 356 puppies, detected vWD in another 19 dogs. Diagnosis was based on non-detectable amounts (< 1.6%) of von Wi llebrand factor antigen (vWF:Ag) in plasma by ELISA. Capillary bleedin g time (CBT) was prolonged (> 10 min) and polybrene cofactor activity (vWF:PbCo) was not detectable in 11 dogs tested. No distinguishable pr otein bands were detected by multimer analysis. As in Scottish terrier s with type III VWD, factor VIII clotting activity (F-VIII:C) in affec ted Dutch kooiker dogs was decreased but considerably less than in hum ans with type III vWD. A recessive mode of inheritance was indicated b y the normal or subnormal but measurable amounts of vWF:Ag in the plas ma of eight pairs of parents of affected dogs. The F-1 offspring resul ting from the experimental mating of two affected dogs consisted of th ree affected males and four affected females. In 39 obligatory carrier s vWF:Ag ranged from 30% to 114% with median and mean vWF values of 64 % and 64.2%, respectively, and was subnormal (< 50%) in only 9 animals .