Equis ISSN 2398-2977

Toxicity: iron

Synonym(s): Iron overload, Iron poinsoning

Contributor(s): Karyn Bischoff, Birgit Puschner

Introduction

  • Cause: 
    • Acute: overdosing on iron containing supplements.
    • Chronic: iron storage diseases: hemosiderosis, hemochromatosis.
  • Signs: 
    • Acute: anorexia, depression, icterus, nervous dysfunction, coagulopathy.
    • Chronic: hemosiderosis: asymptomatic, hemochromatosis: hepatic failure.
  • Diagnosis: history, clinical signs, clinical pathology findings, lesions, and serum or hepatic iron concentration. 
  • Treatment: 
    • Acute: supportive care, including gastroprotectants, pain control, fluids and chelation.
    • Chronic: iron removal through chelation therapy with desferoxamine or phlebotomy.
  • Prognosis: poor.

Pathogenesis

Etiology

  • Acute: high-dose over-supplementation with iron.
  • Chronic: iron storage disease from chronic intake of excessive amounts of iron through diet or drinking water.

Predisposing factors

General

  • Hematinic use in performance horses could increase the risk.
  • Foals have been affected due to over-supplementation.

Specific

  • Excessive absorption of iron occurs in neonates prior to gut closure.
  • Ferrous fumarate-containing supplements for foals (no longer on the market).

Pathophysiology

  • Iron is corrosive:
    • Necrosis of gastrointestinal mucosa.
    • Gastrointestinal upset.
  • Hepatic accumulation:
    • Acute: oxidative damage to lipid membranes, especially in mitochondria:
      • Hepatic necrosis.
      • Multi-organ damage.
    • Chronic: iron storage disease:
      • Hepatic iron accumulation over time.
      • Genetic predisposition.
      • Threshold hepatic iron concentration reached, leading to oxidative damage.
      • Hemosiderosis: asymptomatic iron accumulation.
      • Hemochromatosis: pathologic iron accumulation. 

Timecourse

Acute

  • Gastrointestinal upset early if supplement is ingested.
  • Apparent recovery after 6-24 h.
  • Hepatic failure 12-96 h after dosing.

Iron storage disease

  • Chronic hepatic uptake of iron:
    • Hemosiderosis: asymptomatic accumulation.
    • Hemochromatosis: associated with hepatic fibrosis.

Epidemiology

  • Associated with over-supplementation of foals with a product containing ferrous fumarate in the 1980s.
  • Could be associated with hematinic use in performance horses.
  • Genetic predisposition to iron storage disease (rare).

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Casteel S W (2001) Metal toxicosis in horses. Vet Clin North Am Equine Pract 17 (3), 520-522 PubMed.
  • Pearson E G, Hedstrom O R & Poppenga R H (1994) Hepatic cirrhosis and hemochromatosis in three horses. JAVMA 204 (7), 1053-1056 PubMed.
  • Lavoie J P & Teuscher E (1993) Massive iron overload and cirrhosis resembling haemochromatosis in a racing pony. Equine Vet J 26 (6), 552-554 PubMed.
  • Mullaney T P & Brown C M (1988) Iron toxicity in neonatal foals. Equine Vet J 20 (2), 119-124 PubMed.
  • Acland H M et al (1984) Toxic hepatopathy in foals. Vet Pathol 21 (1), 3-9 PubMed.  

Other sources of information

  • Hooser S B (2012) Iron. In: Veterinary Toxicology Basic and Clinical Principles. 2nd edn. Ed: Gupta R C. Academic Press, USA. pp 517-521.
  • Poppenga R H (2008) Iron Toxicosis. In: Blackwell’s Five-Minute Veterinary Consult, Equine. Eds: Lavoie J P & Hinchcliff K W. Wiley-Blackwell, USA. pp 543.


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