BackgroundEhrlichia canisinfection in dogs can cause thrombocytopenia and clinical evidence of bleeding. It is unknown why some dogs show signs of bleeding whereas others do not despite clinically relevant thrombocytopenia.Hypothesis/ObjectivesActivated platelets, decreased fibrinolysis or both mitigate bleeding tendency. Assess standard hemostatic variables, platelet dynamics, and specialized coagulation testing in dogs experimentally infected withE. canisto evaluate this clinical discrepancy.AnimalsFour healthy laboratory beagles.MethodsDogs were given blood infected withE. canisIV. Platelet indices of activation, platelet aggregometry, antiplatelet antibodies (percent IgG), complete coagulation panel, and thromboelastography (TEG) were measured before inoculation and on weeks 1‐8. Dogs were treated with doxycycline at approximately 5 mg/kg PO q12h between weeks 3 and 4 (day 24). For each variable, 1‐way repeated measures analysis (1‐way ANOVA) with post‐hoc analysis was performed with statistical significance set atP < .05.ResultsDogs had significantly lower platelet counts, evidence of activated platelets, and antiplatelet antibodies duringE. canisinfection. Dogs also appeared hypercoagulable and hypofibrinolytic using TEG as compared with baseline, changes that persisted for variable amounts of time after doxycycline administration. No overt signs of bleeding were noted during the study.Conclusions and Clinical ImportanceActivated platelets and a hypercoagulable, hypofibrinolytic state could explain the lack of a bleeding phenotype in some dogs despite clinically relevant thrombocytopenia. Findings from our pilot study indicate that additional studies are warranted.