Suspected red maple (Acer rubrum) toxicosis with abortion in two Percheron mares

Horses develop severe and often fatal hemolytic anemia after ingesting dried leaves from red maple (Acer rubrum) trees. Toxicosis appears related to an unknown oxidant present in the dried or wilted leaves. This case report describes 2 horses that aborted and developed fatal hemolytic anemia after consuming wilted leaves from red maple (Acer rubrum). While an absolute diagnosis was not confirmed due to lack of proper antemortem and postmortem examinations, red maple toxicosis appeared a reasonable diagnosis based on clinical signs and laboratory findings. Other differentials include equine infectious anemia, autoimmune hemolytic anemia, piroplasmosis, leptospirosis, ehrlichiosis, and other plant or chemical sources of oxidants (onion, garlic, kale, phenothiazines).