Idiopathic Immune-Mediated Thrombocytopenia and Recent Vaccination in Dogs

Background: Vaccination is often cited as a potential cause of immune-mediated thrombocytopenia (ITP) in dogs. Although an association has been documented in humans, particularly in children, this relationship has not been definitively established in dogs. Objectives: To identify the presence of an association between recent vaccination and ITP in dogs. Animals: Forty-eight client-owned dogs with presumptive idiopathic ITP and 96 age-matched, client-owned dogs with non-immune-mediated disease. Methods: Retrospective, case-control study. Dogs were identified through the Veterinary Medical Database (VMDB) and Hospital Information System at Purdue University. Results: The median age at presentation for dogs with ITP was 7 years (range: 2-15 years). The majority of the ITP group was comprised of mixed breed dogs (38%); no pure breed was represented by more than 3 cases. The number of dogs that were vaccinated within 42 days of diagnosis of ITP did not differ significantly (P = .361) between cases of presumptive ITP (4/48, 8%) and the control group (13/96, 14%). Conclusions and Clinical Importance: This study failed to confirm the presence of an association between presumptive idiopathic ITP in dogs and recent vaccination; however, the possibility of an association cannot be completely ruled out based on the small sample populations and requires further investigation.