Causes
Immune-mediated destruction of platelets (a common cause), tick-borne diseases (ehrlichiosis), toxins, drugs, bone marrow diseases, infections.
Diagnosis
A blood count showing low platelets, plus tests to identify the cause.
Treatment
Treatment of the underlying cause. If immune-mediated, immunosuppressants. Supportive care and, in severe bleeding, a transfusion.
Prevention
Tick control, and avoiding toxins and unsuitable medications.

