Introduction

• Cause: anemia may be due to decreased red cell production and/or increased red cell destruction.
• Low grade anemia due to reduced red cell production is common in the horse.
• Chronic inflammation is an important cause of anemia.
• In general this anemia is not severe and will resolve when the underlying cause is identified and treated.
• However, it may become profound and may then be slow to recover even after the initial cause is removed.
• Signs: most commonly related to the underlying disease process, but may include lethargy and poor performance.
• Diagnosis: identification of mild to moderate anemia on hematological evaluation.
• Treatment: treatment of the underlying disease should result in resolution of the anemia.
• Prognosis: good.

Pathogenesis

Etiology

• Mediators from abnormal cells selectively bind iron.
• Defects in erythropoietin production may further reduce red cell production.
• Antibodies generated to RBC altered by drug or neoplastic proteins lead to increased RBC destruction.

Predisposing factors

• Chronic disease, inflammatory, immunologic or neoplastic.
• Auto-immune hemolytic anemia   Anemia: auto-immune hemolytic (AIHA)  , secondary to drug reaction or neoplasia.
• Red Maple toxicity.
• Folate deficiency, secondary to prolonged trimethroprim sulfonamide   Trimethoprim  medication (over 30 days).

Pathophysiology

• There are several mechanisms implicated in the development of anemia associated with chronic disease. Anemia occurs when the rate of production fails to meet the rate of destruction:
  • A block in Fe release from storage.
  • Defective bone marrow response to circulating erythropoietin.
  • Decreased RBC life span.
• In terms of chronic microbial infection, anemia is protective. Low iron availability reduces bacterial growth rates.
• Lowered serum iron   Blood: biochemistry - iron  and reduced iron-binding capacity, with increased iron stored in mononuclear phagocytes.
• There appears to be some defect in the transfer of iron to erythrocyte precusor cells, Interleukin-1 has been implicated.
• Red cells become small and hypochromic (pale in color).

Timecourse

• Usually chronic - over weeks or months.

Diagnosis

Treatment