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Bitter root (Apocynum androsaemifolium) is a spindly plant with purplish-red stems and tiny white flowers. It grows wild on plains and hills in the higher elevations, particularly in sandy or gravelly ground and along creek beds and irrigation ditches. This plant contains dangerous cardiac glycoside compounds in its sap which can cause death within twenty-four hours of ingestion. If you see signs of cardiac glycoside ingestion or if you see your horse sampling a plant such as bitter root that contains cardiac glycosides, it should be treated as a medical emergency.
Bitter root plant, also known as hemp dogbane, Indian hemp, and wild cotton, contains cardiac glycosides, dangerous compounds that can interrupt the functioning of the cardiac muscle and cause death within 24 hours.
Cardiac glycosides often take effect rather rapidly and can interrupt the functioning of the heart muscles. Symptoms that can indicate that your horse has eaten a plant that contains cardiac glycosides can include:
There are many varieties of plants that are known to contain naturally occurring cardiac glycosides that can be dangerous to grazing animals. Some of the plants that have developed these chemicals as a defense include:
The bitter root plant (Apocynum androsaemifolium), also known as dogbane or Indian hemp contains dangerous cardiac glycosides in its sap, which are known to disrupt the natural rhythm of the heart muscle. Just one-half to three-fourths of an ounce per 100 pounds of horse can be a fatal dose of this plant.
The identification of the bitter root plant growing near the pasture or stables will help determine the preliminary diagnosis. During the initial examination, the veterinarian will start by gathering as much information as possible relating to the amount of plant material that may have been ingested and how long it has been since it was consumed. A comprehensive history of the affected horse can also provide a great deal of knowledge to the veterinarian, including information about the elements of the animal’s environment, its diet, and the horse’s regular medications, especially as drugs such as steroids, beta-blockers, and even some chemotherapy agents are known to interact negatively with cardiac glycosides.
A biochemistry profile, complete blood count, and urinalysis are also generally done at this time, including the levels of potassium and magnesium found in the blood. If your veterinarian suspects poisoning by cardiac glycoside there are blood tests available to both detect the cardiac glycosides and to monitor their levels of glycosides in the system.
If the bitter root plant material was ingested within the last few hours, then your horse’s doctor will need to perform a gastric lavage procedure in order to remove as much of the toxic material from the horse’s digestive system as possible, and the stomach contents will be submitted for further evaluation. Once the majority of the plant material has been removed from the stomach then activated charcoal is typically administered to the horse as it can prevent further absorption of the cytisine alkaloids into the bloodstream, and magnesium sulfate may be recommended as well.
There are no known antidotes for the toxic alkaloids that are produced by the bitter root plant, so treatments beyond decontamination are usually concentrated on supportive therapies. Supportive treatments for poisoning may include intravenous fluids to prevent dehydration and combinations of electrolytes and sugars in order to adjust for any imbalances that develop during the recovery period, and anti-inflammatory medications may be recommended to control any pain or swelling.
Either recovery or death will typically occur within 24 hours from the first symptoms, and supportive measures are a key factor in the survival of the patient. Ensuring that the recuperating animal has a quiet stall to recover in will help speed recovery. It is especially important for horses that are exposed to cardiac glycosides to avoid further stress on the heart. It is essential to ensure that bitter root plants are not close enough to your horse's daily environment for the animal to sample. It is particularly important to check sandy or gravelly pastures and along fence lines for this plant. A follow-up examination to test the functionality of the liver and kidneys will most likely be recommended as well.
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