Is Fiddleneck Poisonous? – Amsinckia Toxicity for Horses and Humans

Fiddleneck (Amsinckia spp.) is toxic to horses and a documented liver toxin for humans with substantial exposure. This bristly annual weed is common in grasslands and agricultural areas across western North America. Its danger comes from pyrrolizidine alkaloids (PAs), compounds that accumulate in the liver and cause progressive damage. A single large exposure can cause acute liver injury; repeated smaller exposures over time cause chronic, irreversible liver disease.

What Makes Fiddleneck Toxic?

The plant contains pyrrolizidine alkaloids throughout its leaves, stems, and seeds. These compounds are processed in the liver into toxic metabolites that damage liver cells and the blood vessels supplying the liver. The alkaloids do not typically cause immediate illness, which means poisoning can progress silently before symptoms appear.

Who Is Most at Risk?

Horses and livestock that graze in fiddleneck-infested pastures carry the greatest risk. They may consume the plant repeatedly over weeks or months, building up a damaging cumulative dose. Humans are at risk mainly from intentional consumption such as herbal teas made from related plants or from eating seeds, not from casual contact with fiddleneck in the garden or field.

The ASPCA specifically lists fiddleneck as toxic to horses. Dogs and cats do not typically graze on this plant, but pyrrolizidine alkaloids can affect the liver in any mammal with sufficient ingestion.

Which Parts Are Toxic?

The entire plant contains pyrrolizidine alkaloids: leaves, stems, and seeds. Seeds carry a particularly high concentration.

Symptoms of Fiddleneck Poisoning

Horses: Loss of appetite, weight loss, weakness, an unsteady or stumbling gait (sometimes called “walking disease”), jaundice (yellowing of the eyes and gums), and signs of liver failure. Symptoms may not appear until liver damage is already significant, because the liver has considerable reserve capacity.

Humans and children: Acute poisoning causes nausea, vomiting, abdominal pain, and abdominal swelling from fluid accumulation. Liver failure can follow substantial exposure. The practical human risk is from intentional herbal use or seed ingestion, not from touching or brushing against the plant.

What to Do

1. If a child has eaten any part of the plant, call poison control at 1-800-222-1222 (US) immediately.
2. If a horse shows signs of liver disease and has had access to fiddleneck, call your vet and remove the animal from the affected area without delay.
3. Do not wait for symptoms. Pyrrolizidine alkaloid toxicity often has a delayed presentation.

Controlling Fiddleneck in Pastures

• Identify and remove fiddleneck from horse pastures before the growing season each year.
• Do not allow horses to graze heavily infested areas.
• Dried fiddleneck in hay retains its alkaloid content. Check hay sourced from areas where fiddleneck is common.
• Consult an equine veterinarian if you suspect chronic exposure.

Frequently Asked Questions

Is fiddleneck dangerous to touch? Skin contact is not a concern. The risk is from ingestion, not skin exposure.

Can fiddleneck kill a horse? Yes. Both acute high-dose exposure and chronic low-level grazing can cause fatal liver failure in horses. This is the primary reason fiddleneck is considered a serious agricultural weed.

Is fiddleneck dangerous to dogs or cats? The ASPCA specifically flags fiddleneck as toxic to horses. Dogs and cats are not commonly reported victims, but pyrrolizidine alkaloids can harm the liver of any mammal that consumes sufficient amounts. Keep pets from eating the plant.

Do the alkaloids survive in dried hay? Yes. Dried plant material retains pyrrolizidine alkaloids at toxic levels. Horses have been poisoned by hay containing dried fiddleneck.