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Heliotropes are part of the Boraginaceae family, and grow throughout the United States, Europe, Africa, and Western Asia. This short lived annual can be seen in fields, along roadsides, and in gardens, and unfortunately for horses, can be rolled into hay bales. Heliotropes are known for their sweet scented flowers that grow in clusters of blue, purple, or white in the summer. Plants can grow up to 2 feet tall, producing oval shaped, greyish-green, alternately positioned leaves.
Plants in the Heliotropium species are commonly called heliotropes, though other names can include potato weed, barooga weed, turnsole, and girasole. They contain toxic alkaloids which can cause severe liver damage and photosensitivity when ingested by your horse. Symptoms including weight loss, a progressive weakness, digestive and neurological issues, and abnormal behaviors often appear months after ingestion, which is why this type of poisoning is often fatal.
Symptoms of a chronic heliotrope toxicity may not appear until 2 to 8 months after the first ingestion by your horse, and reflect the plant’s liver damaging effects. Neurological symptoms are also seen, including walking disease, a characteristic symptom of the toxic alkaloids in heliotrope. An acute toxicity can occur when a larger amount of this toxic plant is consumed in a shorter time, though it is not as common, and often leads to death due to internal hemorrhaging and sudden liver failure. Signs your horse is undergoing a heliotrope toxicity include:
There are up to 300 types of heliotrope within the species. Common varieties include:
The cause of a Heliotropium plant poisoning is the pyrrolizidine alkaloids contained in the plant, specifically indicine and lycopsamine. These alkaloids can cause liver damage that can lead to failure, and in some cases, photosensitization, wherein a reaction occurs in the skin causing severe rashes and burns to appear when exposed to sunlight.
Most toxicities of this type are chronic, wherein small doses are ingested over a lengthy period of time. Horses do not normally seek out heliotrope, but can consume this plant in contaminated hay or feed, or in certain conditions, such as drought or an overgrazed pasture. Sometimes, horses can show no signs of a toxicity after ingestion has taken place over an entire season, incurring severe liver damage by the second season. All parts of the heliotrope plant are poisonous in both fresh and dried form.
A diagnosis of any plant containing pyrrolizidine alkaloids can be challenging, as symptoms may appear long after exposure. If you have seen your horse eating heliotrope, this plant identification along with any symptoms present may lead your veterinarian to a diagnosis. More often, symptoms are so delayed, you may not connect a plant poisoning to the signs you see in your horse. In these cases, your veterinarian will need to examine your horse and run a series of tests to narrow down a cause.
A urinalysis, along with blood and serum testing, are performed. Often, these can reveal the presence of pyrrolizidine alkaloids. More specific methods include an ELISA test, spectrophotometry, and gas chromatography/mass spectrometry, which can sometimes yield better results. Your veterinarian will also be on the lookout for elevated protein levels in your horse’s blood, and enzyme levels in the serum, which can be indicators of liver disease. A biopsy from the liver in these cases can be taken for further testing. Examination of other tissues can also detect pyrrolizidine alkaloids.
Treatment for a heliotrope poisoning is supportive and symptomatic, as no antidote exists for a pyrrolizidine alkaloid toxicity. Remove your horse from areas heliotrope grows, and ensure his feed and hay are free from contamination of the toxic plant. Dehydration can be treated with fluid and electrolyte therapy, while cases of photosensitivity can be prescribed medicated creams and lotions. In such cases, it is highly important to keep your horse out of sunlight while he recovers.
The diet may be altered, adding in higher amounts of carbohydrates. Since most cases occur from a long term exposure, treatments to reduce absorption in the gastrointestinal tract are usually not recommended. However, vitamin B12 may be used to decrease the toxic effects of the pyrrolizidine alkaloids, while cobalt can help detoxify your horse before liver damage occurs.
Once your horse begins to show signs, it often indicates that irreversible liver damage has occurred, making the chance of recovery poor. Your horse may recover if treatment is begun before liver damage has occurred, and heliotrope is removed from your horse’s reach.
Prevention remains the best way to ensure that your horse does not incur a fatal case of heliotrope poisoning. Herbicides, mowing, and hand-pulling are common ways to remove heliotrope from your property, fields, fence lines, and trails. Since ingestion often occurs through contaminated feed, inspect your horse’s hay for signs of toxic plants.
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