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What is Halogeton Poisoning?

Halogeton poisoning (also known by its botanical name, halogeton glomeratus) in horses occurs when large amounts of halogeton is ingested by the animal in a short period of time.  The poisoning is then caused by the accumulation of the primary toxin sodium oxalate which has an effect on the calcium levels in the horse’s system.  Halogeton poisoning can cause death if sufficient quantities are ingested and that death can occur in as little as 6 hours after consumption.

Halogeton poisoning is defined as poisoning to the host by ingestion of the halogeton plant which causes oxalate and calcium imbalances, some of which can be acute and deadly.

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Symptoms of Halogeton Poisoning in Horses

Here are some of the symptoms you will see in halogeton poisoning and the associated oxalate poisoning:

  • Colic
  • Diarrhea
  • Recumbency
  • Depression 
  • Muscle tremors
  • Swelling of face
  • Gait changes - staggering
  • Coma and convulsions as the disease progresses

Horses that are most at risk include young horses (under age 3 years), performance horses, horses having immune disorders and lactating mares.  

Types  

There are two types of oxalate poisoning:

  • Acute - Happens when a horse ingests large amounts of soluble oxalates (greater than 2% soluble oxalates), results in rapid decrease blood calcium levels and calcium oxalate crystal formation in the kidneys
  • Chronic - Nutritional secondary hyperparathyroidism or “big head” happens when horses have been grazing on hay or pasture forage containing high-oxalate containing grasses or weeds for a period of two months or longer, results in reduced calcium levels which affects bone integrity and makes fractures more likely

Causes of Halogeton Poisoning in Horses

As noted above, the primary toxin in halogeton poisoning results from sodium oxalates. When horses eat the plant, as the digestive system breaks it down, the sodium oxalates attach themselves to the calcium in the digestive tract and this attachment prevents the calcium from being absorbed and utilized by the various cells throughout the body that need it.  As in the human body, when cells can’t get the calcium needed to function as they were intended, they take it from the bones of both species.  This reallocation of calcium works for the muscles and central nervous system but it takes a huge toll on the skeletal system.  

Depending on whether the type of poisoning is acute or chronic, the clinical signs of halogeton poisoning can present anywhere from 2 to 8 months after the equine has been introduced to the plant in his pasture grazing.  This poisoning can be particularly devastating to weanlings, yearlings and lactating mares due to the increased demand of the body for the calcium in these various developmental stages of life.  These are also the stages of life in which the horse will require greater amounts of feed or forage to fuel the developing equine body.

Diagnosis of Halogeton Poisoning in Horses

Diagnosis of this condition will be done by your veterinary professional who will incorporate your complete history with his thorough physical examination, noting areas of swelling or edema.  He will also likely need to get samples of blood and urine to determine the blood composition especially as it applies to calcium and phosphorous levels and ratios, as well as testing the urine for crystallized sodium oxalates which are known to form in the kidneys with this malady.  

As your veterinary professional seeks to ascertain the type of poisoning and the degree of severity of which the horse is suffering, he will likely also utilize radiographic imaging (x-rays) to identify fractures of varying degrees and types which are also known to be the result of the osteopenic condition that results from reduced levels of calcium.  Once the results of this testing are received, combined with your history and his physical examination of the afflicted horse, an appropriate treatment plan will be developed and initiated.

Treatment of Halogeton Poisoning in Horses

Removal of the horse from the source of halogeton should be the first step taken and it should be taken immediately upon discovery of the above symptoms.  The horse should be removed and placed in a safe area when he can be fed  plenty of clean, good quality feed and water. The horse should be kept in a safe, peaceful and restful environment while treatment is administered -- and, depending on the condition of the horse and the severity of the poisoning, this treatment can take up to 12 months to complete the remineralization of your horse’s bones.

To that end, your vet will likely recommend supplementation of rock phosphate, dicalcium phosphate and limestone in various amounts mixed with molasses being fed to the afflicted horse either weekly or daily for approximately 6 months.  Commercial supplements are also available for daily use as recommended by your vet.  The radiographic imaging will likely need to be repeated during the treatment phase to ascertain appropriate healing and resolution of the poisoning.

Recovery of Halogeton Poisoning in Horses

Under normal circumstances, the consumption of large quantities of this plant is generally not an issue because most pastures contain a fair amount of other forage in addition to the halogeton so the horse doesn’t get as large a percentage of it as forage.  Since horses have a selective palate, they tend to avoid most poisonous plants as they just don’t taste as good as other types of forage plants.  However, this particular plant, unlike some others which are toxic to your horse, doesn’t taste badly to them.  They will graze contentedly on it, especially if they are allowed to get very hungry or thirsty.  If you wish to graze your herd in pastures containing halogeton, then it would be prudent for you to introduce them gradually to the plant by allowing them to graze in those areas for short periods of time and at times when they are not ravenously hungry or thirsty.  Their bodies will adapt to the toxin if it is introduced slowly and it isn’t the primary source of food.

This condition is potentially deadly for your equine so awareness of the plant and the symptoms associated with poisoning or toxicity should be a primary concern for all horse owners.  When they have ingested toxic amounts of halogeton, emergent medical care is absolutely imperative if you wish to save the life of your horse and.  Get acquainted with the properties of halogeton and what it looks like at the various stages of its life cycle so that you can identify it in your pastures and potentially in any hay harvested from pastures.