Oleander is an evergreen shrub that is often found in Arizona.  However, despite its beauty, it is an extremely toxic plant that everyone should be aware of.  This plant is toxic not only to your horse, but to your other pets, animals, and yourself.

Where it is found:
Oleander (Nerium oleander) originated in the Mediterranean region of the world and is commonly seen in the southwestern United States, especially Arizona and California.  Oleander’s relatives, laurel, yellow oleander, and dogbane are equally as toxic but less likely to be found to be growing in Arizona but may be an ornamental addition to your backyard.

Plant identification:
Oleander is a shrub belonging to the evergreen family and typically grows to a height of approximately 20-feet but is often trimmed to a medium-sized bush in more suburban areas.  It has long, slender, dark-green leaves that have parallel veins.   The leaves usually grow in singles or clusters of threes.  The bark is smooth and green in young trees and turns brown in color in aged plants.  The flowers are found in clusters at the end of the branches.  They can be red, pink, or white in color and bloom in the early spring or summer.

Symptoms:
Unfortunately, most horses that have eaten this plant are found dead.  However, if the horse is alive, they usually have symptoms of colic or they can have excessive salivation, weakness, seizures, diarrhea, etc.  These symptoms usually start within 6-8 hours after they have eaten the plant, so early detection is key.

Toxicity:
While all parts of the oleander plant are deadly, dried leaves are the most toxic.  This plant is bitter and therefore usually avoided.  Animals are most often affected because they have eaten clippings or trimmings, or the animal drinks water that is contaminated with leaves in or near the water source.  All animals and humans are at risk and can be affected by this plant.  Only a small amount of oleander is needed to intoxicate the horse.  As little as seven leaves can be deadly to an adult-sized horse.  Foals can be at risk too.  If the mare ingests a piece of the plant, her body metabolizes it and excretes it in the milk, thereby exposing the foal.

Prevention:
Since there is no cure or antidote for oleander, the best way to prevent your horse from getting intoxicated is to remove the plant completely.  Keep in mind that leaves can blow into the pasture from neighboring areas so be aware if your surroundings.

First and foremost, early detection is key.  If you suspect that your horse has eaten any part of the plant, notify your veterinarian immediately.  Your horse’s best chance of survival is early veterinary intervention.