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What is Inkberry Poisoning?

Ilex opaca, or Inkberry, is a variety of Holly that is native to the eastern and south-central portions of the United States. It typically reaches heights of 33 to 66 feet tall, has leaves that are green and glossy, light gray bark with a lumpy texture, and the female plants produce small red berries. These Inkberry plants contain ilicin as well as saponins throughout the plant, although only the green, unripe berries generally have a concentrated enough dose of these noxious substances to cause any symptoms at all.

The unripe berries of the Inkberry plant, or Ilex opaca, contain noxious compounds that can cause distress to your horse if he eats sufficient quantities of the fruit.

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Symptoms of Inkberry Poisoning in Horses

The symptoms of poisoning by Holly plants are nonspecific and may mimic other dangerous poisons. If you are unsure of the cause of the symptoms, a visit with your horse’s doctor may be needed. Symptoms you might see if your horse has ingested a large number of unripe berries from the Inkberry plant include:

  • Abdominal pain
  • Depression
  • Diarrhea
  • Drooling
  • Lethargy
  • Vision problems

Types

The American Holly plant (Ilex opaca) is not the only plant with that is commonly known as Inkberry. Other plants that may go by the moniker of inkberry include:

  • Cestrum diurnum - Although this plant is sometimes known as Chinese Inkberry, it is more commonly referred to as Day Blooming Jasmine; this evergreen is potentially fatal to horses
  • Cestrum laevigatum- Known also as Chilian Cestrum, this shrub from South America, is also quite toxic but is rarely found in the United States
  • Phytolacca americana - This herbaceous plant, known more commonly as Pokeweed, is native to North America; although it is completely unrelated to the Holly plant, pokeweed also contains saponins in conjunction with several detrimental acids

Causes of Inkberry Poisoning in Horses

A bitter alkaloid in Inkberry plants known as ilicin, as well as several saponins cause the symptoms of intoxication. All parts of the plant contain trace amounts of these compounds, but the unripe berries contain the greatest concentration of the saponins. The concentration of saponins in the berries decrease dramatically during the ripening process.

Diagnosis of Inkberry Poisoning in Horses

If you discover your pet consuming an Inkberry plant with unripened berries or if you find Inkberry growing in the pasture the horse grazes in or around the stables then the correct identification of the plant combined with the symptoms may be sufficient to make a preliminary diagnosis of Inkberry poisoning, however, the symptoms can mimic those of more serious poisonings, so further testing is required.

The veterinarian will collect information about the amount of plant material ingested, the ripeness of the berries, and approximately how long ago this occurred and a comprehensive history of the affected horse will 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. Standard blood tests, including a complete blood count and a biochemical profile, will help to rule out several toxins and infections that may have similar symptoms. Plant material from undigested Inkberry leaves or berries may also be found in the feces.

Treatment of Inkberry Poisoning in Horses

If the symptoms began within the last few hours, then decontamination treatments are likely to be started even before a definitive diagnosis has been made, as signs generally point to some form of poisoning. Decontamination treatments consist of a gastric lavage procedure, completed in order to remove as much toxic material from the horse’s digestive system as possible, typically followed by the oral administration of activated charcoal in order to prevent further absorption of the toxins, in this case, the ilicin and various saponins, into the bloodstream.

There are no known antidotes for the noxious compounds that are produced by the plants in the Ilex family, so remedies beyond decontamination are usually concentrated on supportive treatments. Supportive therapies for poisoning cases 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. Fortunately, the recovery period is quite short in most cases, only spanning a few hours.

Recovery of Inkberry Poisoning in Horses

In most cases, horses will recover from poisoning from this variety of Holly swiftly, within just a few hours of the onset of symptoms, and fatal instances of poisoning by these plants are exceedingly rare. Most equines are not attracted to eating any type of Holly plant unless there is very little forage available and because the toxin is mild in most parts of the plant, this type of intoxication is relatively rare. Ensuring that the fields that your horse spends time grazing in has a large variety of adequate grazing flora will decrease the possibility of poisoning by this plant.