Equis ISSN 2398-2977

Anemia: overview

Contributor(s): Joe Bertone, Prof Derek Knottenbelt, Ruth Morgan, Han van der Kolk

Introduction

  • The life-span of equine erythrocytes is about 100 days.
  • Anemia is defined as a deficiency of erythrocytes either in number or volume or both.
  • Cause:
    • Hemorrhage: internal vs external, acute vs chronic.
    • Hemolysis: intravascular vs extravascular, immune-mediated (primary or secondary), direct toxic damage, oxidative damage, infectious disease.
    • Increased use/shortened half-life of RBCs.
    • Decreased production.
  • Signs: depends on the degree of chronicity of the anemia. Common features include pallor or jaundice, lethargy, weakness, collapse, poor performance/exercise intolerance.
  • Diagnosis: hematological evaluation, including a blood smear, is essential for the identification of anemia.
  • Treatment: depends on the cause of the anemia.
  • Prognosis: depends on the cause of the anemia.

Pathogenesis

Etiology

  • Hemorrhage: external or internal blood loss.
  • Hemolysis: destruction of red blood cells:
    • Immune-mediated (primary or secondary).
    • Toxic: direct, eg following DMSO administration, or oxidative damage, eg red maple leaf or onion ingestion.
    • Infectious disease, eg equine infectious anemia, babesiosis, ehrlichia.
  • Anemia of chronic disease: increased use and shortened red blood cell lifespan.
  • Failure of production: myelophthisic disease, eg bone marrow neoplasia, renal disease resulting in reduced production of erythropoietin.

Predisposing factors

General

Pathophysiology

  • Anemia can be induced via several mechanisms.
  • Hemorrhage: external or internal blood loss.
  • Hemolysis: destruction of red blood cells:
    • Immune-mediated (primary or secondary).
    • Toxic: direct, eg following DMSO adminitration, or oxidative, eg red maple leaf or onion ingestion.
    • Infectious disease, eg equine infectious anemia   Equine infectious anemia (EIA)  , babesiosis   Babesiosis  , ehrlichiosis   Potomac Horse Fever 
  • Anemia of chronic disease: increased use and shortened red blood cell lifespan.
  • Failure of production: myelophthisic disease, eg bone marrow neoplasia, renal disease resulting in reduced production of erythropoietin.
  • Some diseases induce anemia by more than one mechanism, eg EIA, causes both hemolysis and reduced red cell production.
  • Lymphosarcoma might induce anemia both via myelophthisis and via immune-mediated mechanisms.

Timecourse

  • Anemia in case of equine infectious anemia   Equine infectious anemia (EIA)  is progressive and cyclic.
  • Anemia following (severe) blood loss   Anemia: blood loss  /trauma is seen suddenly - not always external bleeding.
  • Rapid onset anemia:
  • Slow onset anemia:
    • Bone marrow suppression.
    • Parasitism.

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.
  • Hollis A R & Corley K T T (2011) Initial experience of ultrapurified bovine haemoglobin use in horses. Equine Vet Educ 23 (11), 562-568 VetMedResource.
  • Hart K A (2008) Evaluation and management of anaemia in the post operative colic patient. Equine Vet Educ 20 (8), 427-432 VetMedResource.
  • Piercy R J, Swardson C J & Hinchcliff K W (1998) Erythroid hypoplasia and anemia following administration of recombinant human erythropoietin to two horses. JAVMA 212, 244-247 PubMed.
  • McConnico R S, Roberts M C & Tompkins M (1992) Penicillin-induced immune-mediated hemolytic anemia in a horse. JAVMA 201, 1402-1403 PubMed.
  • Mair TS, Taylor F G & Hillyer M H (1990) Autoimmune haemolytic anaemia in eight horses. Vet Rec 126, 51-53 PubMed.


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