Aflatoxin Poisoning in Horses

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Poisoning by Aflatoxins in Horses

Aflatoxins are one of many different types of chemicals that have proven to be toxic to horses, and they can come in many forms. Usually produced by a type of fungus called Aspergillus flavus, aflatoxins have been found in several different types of foodstuffs, usually to the surprise of the horse owner.

The Aspergillus mold is a naturally occurring fungus that proliferates in humid conditions, particularly in crops, hay, vegetation, soil, and grains. Aflatoxins primarily affect the liver where they lead to problems with protein synthesis, blood clotting, and fat metabolism. Aflatoxins in other species are known to be carcinogenic and can be immunosuppressive as well.

Symptoms and Types

Acute Aflatoxin Poisoning

  • Severe depression
  • Anorexia
  • Fever
  • Abdominal pain (colic)
  • Yellowing of the mucous membranes (jaundice)
  • Bloody feces
  • Bleeding from the nose 
  • Ataxia (loss of coordination)
  • Recumbence (lying down)
  • Muscle spasms
  • Convulsions
  • Death

Chronic Aflatoxin Poisoning

  • Weight loss
  • Anemia 
  • Rough hair coat
  • Jaundice
  • Diarrhea
  • Formation of hematomas beneath the skin


  • Ingestion of food that is contaminated with aflatoxins. These toxins can be present in both grains and forages.


Definitive diagnosis of aflatoxicosis is difficult as the clinical signs are non-specific and mimic a variety of other equally serious conditions. Blood work will show elevated liver enzymes and other non-specific abnormal changes. There are, however, no samples that can be taken from a live horse that will definitively diagnosis the ingestion of this toxin. Sampling the contaminated feed is the best way to obtain a diagnosis.

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