Nightshade Poisoning in Horses - Causes, Treatment and Associated Conditions

Key takeaways

Nightshade poisoning is a rare and potentially life-threatening condition in horses caused by the ingestion of plants in the nightshade family (Solanaceae spp.), including potatoes.

Symptoms of nightshade poisoning include abdominal pain, diarrhea, incoordination, and seizures
There is no specific diagnostic test for nightshade poisoning; diagnosis is generally based on symptoms, history of exposure, bloodwork, and feed analysis
Once diagnosed, treatment options include administration of neostigmine, IV fluid therapy, and activated charcoal
Prognosis varies from guarded to poor depending on the amount of toxin ingested and the promptness of treatment
The only way to completely prevent poisoning is to ensure no contact with nightshade plants, including potatoes

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A closer look: Nightshade Poisoning in Horses

Nightshade poisoning is a rare and potentially life-threatening condition in horses.

There are over 70 different plants belonging to the Solanaceae family including:

Black nightshade (Solanum nigrum)
Bittersweet nightshade (Solanum dulcamara)
Common or American nightshade (Solanum americanum)
Deadly nightshade (Atropa belladonna)
Potatoes (Solanum tuberosum), particularly the peels

Species of nightshade grow all over the world, including rainforests and deserts.

If horses have access to alternative healthy feed, they tend not to eat nightshade plants due to their unpalatability.

The most common source of nightshade exposure in horses is the presence of nightshade plants in baled hay. The Solanum family also includes the potato, so preventing access to potatoes or potato waste is recommended.

If ingestion of nightshade is witnessed or suspected, prompt medical attention is warranted as early treatment increases the chances of recovery.

The lethal dose is between one and ten pounds.

Risk factors

Nightshade toxicosis can also affect the nervous system in some cases.

This form of poisoning is rare in horses and in general, horses that have adequate access to uncontaminated feed are unlikely to eat species of nightshade.

Possible causes

Nightshade poisoning is caused by ingestion of plants belonging to the Solanaceae family. Nightshade plants contain an array of toxic components that, once ingested, affect the animal’s gastrointestinal and nervous systems.

Main symptoms

Nightshade toxicosis primarily causes symptoms in the digestive tract.

Testing and diagnosis

There is no specific diagnostic test for nightshade poisoning. Horses presenting symptoms of nightshade toxicosis generally undergo the following diagnostics:

Physical examination
Bloodwork
Feed analysis
Analysis of stomach contents

Steps to Recovery

Once diagnosed, treatment options include:

Neostigmine: a medication that has the opposite effect of the toxin within the body
Activated charcoal to prevent further absorption of toxins
IV fluid therapy
Anti-seizure medication
Anti-inflammatory medications

Note: Always consult a veterinarian before administering medication to animals, including activated charcoal.

Once treated, stall rest is required until recovery is complete.

Prognosis for nightshade poisoning varies from guarded to poor and depends on the amount of toxin ingested and the promptness of treatment. Cases of ingestion caught before symptoms develop have the best prognosis, with a good chance of recovery.

Horses that ingest more than 10 pounds of nightshade carry a poor prognosis.