What is Prunus Poisoning?
Including both trees and shrubs, the genus Prunus includes over 200 species. Plants of this genus are particularly important for their stone fruits that include cherries, peaches, plums, nectarines, apricots, and almonds. These fruits are safe when eaten by people, however there are cyanogenic glycosides in the leaves, shoots, bark and pits of the fruit that can lead to poisoning in horses. The highest concentration of the possible toxin is typically in young, fast growing leaf tissue and the seed of the fruit, however, all parts of the plant contain cyanogenic glycosides and should be kept from animals.
Cyanogenic glycosides present in the species of the genus Prunus can turn into cyanide, leading to poisoning in horses.
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Symptoms of Prunus Poisoning in Horses
Should your horse ingest Prunus virginiana, or chokecherry, you may notice the following symptoms:
- Lack of muscle coordination
- Difficulty breathing
- Flared nostrils
- Inability to control bowel movements and urination
If enough leaves are ingested, death can occur within minutes.
There are over 200 species within the genus Prunus. The species include:
- Prunus virginiana - Chokecherry
- Prunus pensylvanica - Pin cherry
- Prunus serotina - Black cherry
- Prunus nigra - Canada plum
- Prunus americana - American plum
In an uncontrolled environment, pin cherry and black cherry likely present the most risk for being accidently ingested by a horse. Other plants that may be seen growing wild on pastures include peach, apricot, plum, sweet cherry and sour cherry.
Causes of Prunus Poisoning in Horses
Cyanogenic glycosides, specifically prunasin, prulaurasin and amygdalin, are the toxins found in the Prunus family. Prunus plants are poisonous because they produce cyanide. The production of cyanide occurs when the different parts of the plant come together. As the toxins are usually stored in the vacuole of the plant cell, they won’t harm the typical metabolic process of the plant. Should the membrane of the vacuole be broken whether because of damage or stress, there are enzymes in the plant cell and micro-organisms in the stomach that can turn the glycosides into hydrogen cyanide.
Cyanide can harm your horse because it reacts with iron that is present in his body and will cause cellular respiration to cease. It will also stop oxygen from traveling along the bloodstream causing your horse to suffocate.
All of the parts of Prunus virginiana include cyanogenic glycosides (specifically amygdalin and prunasin). Only a small amount of cyanogenic glycosides need to be ingested for the horse to be poisoned; should the horse take in 0.25% of their weight (for example 2.5 pounds for a 1000 pound horse) of the fresh green leaves, the poison can be fatal.
Diagnosis of Prunus Poisoning in Horses
When it comes to prunus poisoning, which progresses rapidly, in many cases the animals are found dead in the pasture. Only if the animal is found shortly after consuming the plant are other symptoms noted.
It can be very hard to ascertain what caused the poisoning in your horse as the ingestion of many toxic substances will lead to the same or similar symptoms. It is recommended to look around the area where your horse has been to see if you can locate any poisonous substances.
It is important that the poisonous substance be determined so that the correct treatment can be delivered. Should nothing be found in the area where your horse has been, their feces, stomach contents or body tissues can be analyzed. Unfortunately when it comes to prunus poisoning, there is not always time to get these results.
Treatment of Prunus Poisoning in Horses
Should your horse experience poisoning from a prunus plant, treatment is possible, though time is of the essence. Toxic reactions from cyanide poisoning have a very rapid progression and in many cases the veterinarian is unable to get there in time to help the horse. Should your horse be treated right away, there is a chance for him to recover. Recommended treatment involves intraperitoneal or intravenous injection of a mixture of 20mL of a 10% solution of sodium thiosulfate along with 10mL of a 10% solution of sodium nitrite. Should the poisoning have progressed, intravenous treatment is imperative. While your horse is undergoing treatment, you will want to help him to remain calm.
Recovery of Prunus Poisoning in Horses
If your horse experiences prunus poisoning and responds to treatment, you will want to follow the recommendations of your veterinarian to ensure the best outcome for him. It is likely that follow up appointments will be necessary to confirm that your horse is continuing to improve and to adjust treatment as necessary.