Moldy Sweet Corn Poisoning (Fumonisin Toxicity and ELEM) in Horses

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Key takeaways

Fumonisin toxicosis is a life-threatening condition that occurs when horses ingest fumonisin, a fungal toxin produced by Fusarium verticillioides or F. proliferatum fungi which grow on sweet corn. 

  • Fumonisin can cause two separate syndromes: equine leukoencephalomalacia (ELEM) or liver damage
  • Common symptoms include uncoordinated movement, blindness, circling, recumbency, and sudden death
  • There is no antidote for fumonisin poisoning, and treatment options, which are limited, involve removal of contaminated corn as well as symptomatic and supportive care
  • Even with treatment, most animals die after the onset of symptoms
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A closer look: Moldy Sweet Corn Poisoning (Fumonisin Toxicity and ELEM) in Horses

Fumonisin toxicosis is a rare condition in horses. It mainly affects animals that are fed corn-based diets.

Moldy sweet corn toxicosis is a life-threatening fungal poisoning and must be treated as an emergency. Once symptoms of fumonisin toxicosis develop, most horses have a guarded to grave prognosis.

Risk factors

Moldy sweet corn poisoning is rare in horses. It is more common in horses on corn-based diets. Horses living in humid and warm areas are at a higher risk of toxicosis.

Moldy corn toxicosis can cause two separate syndromes:

Neurotoxic form: Equine leukoencephalomalacia (ELEM) is the most common form of fumonisin toxicosis. The ingestion of large doses of the toxin over a short period causes ELEM.

Hepatotoxic form: rarer and generally occurs when small doses of toxin are ingested over an extended period.

Possible causes

Moldy sweet corn toxicosis is caused by the ingestion of corn contaminated with fumonisin, a fungal toxin produced by Fusarium verticillioides and F. proliferatum fungi.

Fumonisin can be found in corn and corn-based products that become moldy as the result of excessive moisture.

Main symptoms

Testing and diagnosis

Horses presenting with symptoms of moldy sweet corn toxicosis generally undergo the following diagnostics:

  • Physical examination
  • Neurological examination
  • Cerebrospinal fluid analysis (spinal tap)
  • Blood work
  • Feed analysis
  • Liver biopsy

Steps to Recovery

The first step in treatment is removing contaminated feed.

Once the source of the toxin is removed, treatment focuses on supportive and symptomatic therapy, including:

  • IV fluids
  • Activated charcoal to prevent further toxin absorption
  • Medications to protect the liver
  • Sedation

Note: always consult a veterinarian before administering medication, including activated charcoal.

No specific antidotes are available, and in the majority of cases, horses die as the result of fumonisin ingestion.

Most cases of fumonisin toxicosis carry a very poor prognosis, with most animals dying shortly after the onset of symptoms.

In mild cases, the prognosis is guarded, and animals that are able to recover can suffer from lifelong neurological deficits.


Moldy sweet corn toxicosis is not contagious.

Prevention strategies include:

  • Analyzing corn and corn-based products before feeding
  • Proper storage of corn in dry places
  • Avoiding long-term storage of feed

Is Moldy Sweet Corn Poisoning (Fumonisin Toxicity and ELEM) in Horses common?

Fumonisin toxicosis is uncommon overall, but is more common in horses that are fed corn-based diets.

Typical Treatment

  • Removal of fumonisin source
  • Supportive and symptomatic care
  • No specific treatment


Michelle S. Mostrom , DVM, MS, PhD, DABVT, DABT - Writing for MSD Veterinary Manual
Carla Sommardahl DVM PhD DipACVIM(LA) - Writing for Vetlexicon
Radka Borutova, MVD, PhD, NutriAd International - Writing for The Horse
Press Release - Writing for The Horse

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