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What is Blackjack Pine Poisoning?

The blackjack pine tree is known by many other names and is known for its heavy wood and thick bark. It is one of the largest pine trees in the United States, reaching up to 250 feet tall and 325 inches in diameter. It grows brownish-red pine cones about four or five inches in length and long, thick pine needles. There are many varieties and subspecies of blackjack pines, but many are referred to as Ponderosa pines. However, they are all toxic to horses. In horses that are not pregnant, the symptoms are caused by the digestive upset, central nervous system damage, and renal lesions.

Blackjack Pine (Pinus ponderosa) trees contain isocupressic acids, most concentrated in the needles, which can cause abortion in pregnant mares and gastric distress in others. In some cases, the effects can be much worse, causing central nervous system damage, renal damage, and even death. This usually only happens in cases of large consumption. Although the majority of abortion cases were reported in cattle and sheep, horses have been known to suffer similar effects.

Abortions usually occurring between 2 and 14 days after consumption while the gastric and central nervous system effects are evident within minutes to hours. The abortion begins with a mucous discharge and mild contractions and the horse may need assistance in delivering. After she aborts, a uterine infection called metritis is common and may cause serious symptoms such as paralysis. In addition, your mare may no longer be fertile.

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Symptoms of Blackjack Pine Poisoning in Horses

The symptoms vary quite a bit, depending on how far along in pregnancy your mare is at the time of consumption. In the first trimester, there may be no symptoms and your horse may not even abort after eating the needles. Similarly, in horses that are not pregnant, there may be no visible effects or your horse may have mild symptoms such as abdominal pain or severe effects such as convulsions and paralyzation. In some cases, consumption of the blackjack pine may even be fatal. Some of the most common signs include:

  • Mucous discharge (in pregnant mares)
  • Abdominal cramping and contractions (in pregnant mares)
  • Needing help with delivery (in pregnant mares)
  • Severe pain and contractions (in pregnant mares)
  • Vague central nervous system symptoms (confusion, dizziness, head pressing, drooling)
  • Renal lesions (increased thirst and urination, listlessness, edema)
  • Convulsions
  • Paralysis
  • Death (rare)

 Types

The blackjack pine’s botanical name is Pinus ponderosa, which is in the Pinaceae family. Some of the various types and subtypes of blackjack pine trees include:

  • Bull Pine
  • Callaham Ponderosa Pine
  • Central High Plains Pine
  • Columbia Ponderosa Pine
  • Pacific Ponderosa Pine
  • Rocky Mountains Ponderosa Pine
  • Washoe Pine
  • Western Yellow Pine
  • Yellow Pine

Causes of Blackjack Pine Poisoning in Horses

There is a diterpene acid in the blackjack pine that is called isocupressic acid. It is found in the entire tree but most concentrated in the needles. Central nervous system changes, along with kidney issues and gastrointestinal distress are effects caused by the toxins.

Diagnosis of Blackjack Pine Poisoning in Horses

There are many tests that can detect blackjack pine poisoning complications such as spontaneous abortion and renal damage, but determining whether blackjack pine poisoning is the cause is more of an elimination examination. The veterinarian will need to know what happened exactly, medications your horse is taking, and your horse’s recent injuries and illnesses. Bring along the medical and immunization records if you have them. The veterinarian will do a complete and thorough physical to assess your horse’s overall body condition, vital signs, behavior, and palpations of the major muscles and organs. Next, a lameness examination will be performed and you may be asked to walk your horse around a bit so the veterinarian can check muscle performance in motion.

The usual blood tests will be done such as a complete blood count (CBC), packed cell volume (PCV), biochemistry analysis, blood urea nitrogen (BUN), and total glucose. The tests should indicate an increase in calcium and urea, decreases in chloride and sodium, and your horse may be anemic. A urinalysis with low specific gravity is also a sign of blackjack pine poisoning. An ultrasound will be done to verify that your horse has had an abortion and whether the afterbirth was expelled or not. It can also show signs of inflammation and infection. An x-ray may also be needed to check for other abnormalities.

Treatment of Blackjack Pine Poisoning in Horses

Treating blackjack pine poisoning is similar to other equine poisonings, including decontamination, medication, fluids, oxygen, and hospitalization.

Decontamination

In order to decontaminate your horse, a gastric lavage will be done by inserting a gastric tube and pumping saline into the stomach. This will wash away plant particles and toxins that have not been absorbed. Activated charcoal is given by mouth to absorb any remaining substances that are still in the gastrointestinal tract.

Fluids and Oxygen

If your horse is having respiratory problems, oxygen will likely already have been given. Intravenous (IV) fluids will also be given to help circulation and flush the kidneys. This is extremely important for renal functioning and also helps prevent dehydration.

Medication

Chloride and sodium replacements are given right away, antibiotics may be given for infection, and furosemide for fluid retention. In addition, phenylbutazone may be provided for pain.

Hospitalization

The veterinarian will probably suggest hospitalization for observation and to continue providing medical treatment when needed. The length of stay depends on your horse’s response to treatment and overall health. Mares who have aborted a fetus may need further evaluation.

Recovery of Blackjack Pine Poisoning in Horses

Your horse’s prognosis is fair to guarded depending on the complications. If there is renal damage, lowered kidney function may decrease your horse’s lifespan. However, in the case of a mild to moderate toxicity, recovery is possible; with continued treatment and follow-up care, your horse can still live a normal lifespan.