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What is Field Bindweed Poisoning?

Convolvulus arvensis is part of the morning glory family, and is considered one of the most invasive weeds in agricultural farming throughout many areas of the world, including North America, Europe, and Africa. This perennial vine creeps along the ground, or twines up plants or nearby objects, spreading up to 10 feet in length. It boasts alternate, arrowhead-shaped leaves, and white, pink or purple trumpet-shaped flowers that bloom from April to October. Field bindweed is hard to control, as it can reproduce from its deep and extensive root system, or from seeds that can survive dormant in soil up to 60 years. You can find this vine in cultivated fields, gardens, pastures, roadsides, and waste areas.

Field bindweed, also known as creeping jenny, perennial morning glory, sheepbine, or just bindweed, is a creeping vine that contains toxic alkaloids. When consumed, these toxins can cause disruptions to your horse’s digestive and nervous systems, often seen as a progressive weight loss and colic. Severe poisonings can become fatal.

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Symptoms of Field Bindweed Poisoning in Horses

The toxins in field bindweed affect the digestive and nervous systems. Signs can include: 

  • Weight Loss
  • Colic 
  • Diarrhea
  • Abdominal pain
  • Dry mouth
  • Weak and rapid pulse
  • Dilated pupils
  • Incoordination
  • Convulsions
  • Coma
  • Death

Field bindweed can accumulate high levels of nitrates. Signs of a nitrate poisoning can appear within hours, and can end in a fatality. Chronic nitrate poisoning can affect reproductive and thyroid functions. Symptoms of a nitrate poisoning can include:

  • Drowsiness 
  • Weakness
  • Brown mucous membranes
  • Increased heart rate
  • Increased breathing rate 
  • Muscle tremors
  • Unsteady gait
  • Staggering
  • Lying down
  • Abortions 
  • Collapse

Causes of Field Bindweed Poisoning in Horses

Field bindweed contains toxic alkaloids in all of its parts, though the highest concentrations are in the seeds. These toxins include the pyrrolidine alkaloids hygrine and cuscohygrine, and the tropane alkaloids tropine, tropinone, and pseudotropine. Pseudotropine is believed to be the major cause of symptoms involving the autonomic nervous system and gastrointestinal tract.

If the field bindweed that your horse has ingested is high in nitrates, he can suffer from nitrate poisoning. This occurs when an excess of nitrates enters the bloodstream from the digestive tract, where it hinders the ability of the blood to carry oxygen. This action starves the body’s tissues of oxygen, causing the symptoms seen in this type of poisoning. Plants containing as little as 1% nitrates can be lethal.

Diagnosis of Field Bindweed Poisoning in Horses

A diagnosis of a poisoning due to field bindweed is based on symptoms and a history of exposure. If you suspect your horse has eaten field bindweed, bring a sample of the plant to be correctly identified by your veterinarian.

More often, symptoms are seen without the owner having knowledge that a certain plant was ingested. Your veterinarian may perform a physical exam and run a series of tests to narrow down the cause of your horse’s symptoms. Tests can include blood and serum testing, and a urinalysis, all of which can detect the presence of nitrates or alkaloids. Further testing can include a rectal palpation and a laparotomy, which can reveal a thickened intestine, a sign of this type of toxicity.

Treatment of Field Bindweed Poisoning in Horses

There is no specific treatment for field bindweed toxicity. Treatment of any plant poisoning aims to reduce absorption of the toxins, address any symptoms present, and support your horse’s recovery. Activated charcoal or mineral oil can be administered to reduce absorption of the plant toxins. Supportive treatments can include fluid and electrolyte therapy. Remove your horse from any areas of field bindweed, and inspect his hay for accidental contamination.

If nitrates were found to be present in the diagnosis, a methylene blue solution may be intravenously administered to restore oxygen transport functions. Oxygen therapy may also be needed. Epinephrine can be given to treat any hypotensive effects, while vinegar and mineral oil can reduce the amount of nitrates absorbed into the bloodstream.

Recovery of Field Bindweed Poisoning in Horses

There is not enough research on the rate of recovery from a field bindweed toxicity. Treatment should be started as soon as possible, as severe poisonings, as well as those complicated with accumulated nitrates, can lead to life threatening conditions. 

Prevent your horse from ingesting toxic bindweed through management strategies. Field bindweed can be challenging to control, and will need aggressive removal. Accomplish this by:

  • Monitoring fields, pastures, fence lines and trails for field bindweed
  • Pulling vine wherever plant appears
  • Tilling soil every 2 to 3 weeks for up to 3 years during the growing season to starve root system
  • Using systemic herbicides during bud stage or summer fallow