Thrombocytopenia associated with vaccination of a dog with a modified-live paramyxovirus vaccine.

Thrombocytopenia (10,000/mm3), with hematochezia and melena, appeared in a dog 8 days after it was given modified-live canine distemper, virus vaccine and persisted for approximately 5 days. Clinical investigation discounted other possible causes of thrombocytopenia; the condition was considered to be associated with vaccination. The problem spontaneously resolved. The appearance of thrombocytopenia after modified-live canine distemper virus vaccination is not unknown and may assume a severe form. This condition may be mistaken for idiopathic thrombocytopenia of immune origin, and in other instances, it may contribute significantly to surgical risk if concurrent coagulation disorders are present. Administration of levamisole HCl may alleviate the decrease in platelet count in affected animals.