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What is Senecio Poisoning?

Senecio poisoning will gradually destroy your horse’s liver. Since this occurs over several weeks, sometimes the damage done is too advanced and your horse will need to be euthanized. Treatments are available for senecio poisoning but the disease must be diagnosed early enough for the treatments to be effective.

Senecio, also known as groundsel, is a weed that is found throughout the United States. Toxicity from senecio can take a month or longer to present in horses and that makes it very difficult to determine where your horse found the weed; in their pasture or in their hay.  The symptoms of senecio poisoning in horses are easy to identify since the toxins are pyrrolizidine alkaloids. These are very common in livestock feeds.

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Symptoms of Senecio Poisoning in Horses

Since it takes a month or longer for signs to present, you may not notice right away that your horse is feeling ill or being poisoned. Daily physical checks of your horse are important for early detection of senecio poisoning. If you notice any of these symptoms, call your veterinarian for an appointment.

  • Weight loss
  • Jaundiced eyes
  • Photosensitization
  • Anorexia
  • Dullness of the coat
  • Constipation or diarrhea
  • Tenesmus
  • Blood in the stool
  • Aimless wandering
  • Frenzied or aggressive behavior
  • Interstitial pneumonia
  • Sudden death

Causes of Senecio Poisoning in Horses

Senecio contains pyrrolizidine alkaloids which form toxins over time in your horse’s system. In most cases, it takes at least a month for the toxins to build within your horse’s body and present any symptoms of illness. The toxins affect cell division and eventually cause liver damage. 

It is important to know what is in your horse’s feed including their hay. It is also important to practice diligent pasture management. This means that you walk through your horse’s pasture looking for any potentially poisonous plants and eradicating them from the pasture. You will also want to ensure that your horse’s pasture has plenty of nutrient rich forage.

Diagnosis of Senecio Poisoning in Horses

Once your veterinarian arrives to check your horse, they will ask you about the symptoms that have presented. Many times they will also ask you about your horse’s feed and eating habits.

A full physical examination will be done by your veterinarian and they will collect a fecal sample and urine sample for testing. A complete blood count will also be done so a chemical analysis can be completed to confirm recent exposure to senecio or pyrrolizidine alkaloids. The analysis will focus on the red blood cells and look for any pyrroles that are bound to them. 

While waiting for laboratory results, your veterinarian may make a presumptive diagnosis based on the clinical symptoms and a history of exposure to senecio if the plant is visible in your horse’s pasture or hay. 

To determine the extent of damage already done to your horse’s liver, an ultrasound may be performed. Your veterinarian may also opt to do a biopsy of the liver to better understand how far the disease has spread and the best treatment options for your horse.

Treatment of Senecio Poisoning in Horses

As soon as you suspect that your horse has been poisoned, remove them from their pasture into their stall. Take away any hay and feed. Once your veterinarian makes their diagnosis, they will set up a treatment plan to help sustain your horse. Generally, by the time symptoms present, it is already too late and your horse will most likely not recover. 

A diet that is high in carbohydrates will help to slow the progression of the illness. Do not feed a diet high in protein since protein may precipitate the symptoms and cause death to occur more quickly.

Supportive care will be required and probably hospitalization so your horse can be closely monitored by a trained staff. Intravenous fluid and nutrition therapy will be provided. Supportive treatments for photosensitization will also be given. While undergoing supportive care, the symptoms that have presented will also be treated.

If your horse is showing symptoms of weight loss, jaundiced eyes and photosensitization, there are no effective treatments available or any way to reverse the damage done to your horse’s liver. Euthanasia is usually recommended at this stage.

Recovery of Senecio Poisoning in Horses

Most horses do not recover from senecio poisoning because they do not show any symptoms until the disease has progressed to the point of irreparable liver damage. At that point, many horse owners opt for humane euthanasia rather than attempting supportive care and treating the symptoms.

Keep your horse’s pasture free of senecio and other poisonous plants. If you are unsure of which plants are poisonous to horses, do your research or ask your veterinarian for a guide to show you. Spraying your pasture with a pasture safe herbicide will help in removing unwanted weeds that may be poisonous to your horse.