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The rain lily name comes from the fact that it blooms right after it rains. It is a popular garden plant due to its attractive flowers that come in many different styles and colors. However, it also grows wild and can invade your field without your knowledge. The wild rain lily grows in bunches with clumps of large, star or funnel-shaped blooms that are usually white, pink, or light purple. They are low growing plants only about 3 to 12 inches high and they closely resemble crocuses. The leaves are broad and grassy and tend to blend in with other plants, which is why it is good to check your pastures often. Information is limited on equine rain lily poisoning; however, it is suspected that horses share the same level of toxicity as cattle.
Although there are some lilies that are not dangerous if eaten, the rain lily (Zephyranthes atamasca) is not one of them. Documentation shows that the rain lily is proven to be toxic to cattle, with strong suspicion that horses would be affected in the same manner. In fact, this is one of the more poisonous lilies and it only takes 0.5% of an animal’s body weight to be lethal. There are several phenanthridine alkaloids in the plant that are toxic, which are tazettine, galantine, and lycorine. The symptoms may include nausea, abdominal pain, and even convulsions that can lead to death. It only takes a small amount of the rain lily to cause poisoning, and larger doses may be deadly before you even know your horse consumed any. Also, it is thought to cause renal necrosis in its chronic form, if your horse eats a small amount on a daily basis for more than a few days.
Symptoms of rain lily poisoning will vary depending on the amount that your horse consumed. The signs noted in cattle that may be seen in a horse who has ingested the rain lily are:
The rain Lily (Zephyranthes atamasco) is also known as the Atamasco lily, Fairy lily, or Prairie lily. The Zephyranthes genus has over 70 species, but some of the most common include:
The toxic principle in the rain lily include these phenanthridine alkaloids:
To help the veterinarian get a definitive diagnosis, take a walk about the pasture with him to identify the noxious weeds and to look for areas of heavy forage. Not only will the veterinarian single out the rain lily, he will point out other weeds and flowers that may need to be eliminated from your horse’s grazing area. A physical assessment of your horse’s present condition, a lameness examination, a discussion of recent medical history, and vital signs will be needed. In addition, radiographs (x-rays) and an ultrasound of the kidneys are important in determining if there is any renal damage. Laboratory tests such as a urinalysis, blood tests, and a kidney biopsy are done next. The veterinarian will be looking for protein, glucose, and casts in the urine and an increase in potassium, phosphorus, creatinine, and blood urea nitrogen (BUN).
Treatment documented for cattle would most likely be similar in horses.
Decontamination, fluids, medication, and hospitalization is the usual protocol to treat rain lily poisoning. However, the treatment plan may vary depending on the veterinarian and results of the examination.
Activated charcoal, administered in an effort to absorb the toxins, will be given orally with a gastric tube inserted into the digestive tract.
To flush the kidneys, fluids will be given intravenously. This can also help prevent dehydration from frequent diarrhea.
Some of the drugs used in treating rain lily poisoning in horses include furosemide (Lasix) and mannitol to relieve fluid retention, and dopamine to help with neurological damage.
In severe cases, hospitalization will be necessary. The veterinarian will usually want to keep your horse for 12-36 hours for observation and to provide supportive treatment if needed. Some of these may include electrolytes, oxygen, and additional medications.
Your horse’s prognosis depends on how fast you were able to obtain veterinary help. If your horse ate a large amount of rain lilies, the toxic substances may have already done damage (such as renal necrosis) that cannot be repaired. However, with proper veterinary treatment, chances are still good that your horse will recover.
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