From Dog

Reticulocystosis, defined as increased red blood cells in circulation can result from both physiological and pathological processes.

  • Physiological reticulocytosis

Physiological reticulocytosis is commonly due to bone marrow release of reticulocytes prematurely or splenic contraction. Causes include excitement, exercise and certain drugs such as erythropoietin[1] in dogs with chronic renal disease and adrenalin.

In most cases, reticulocytosis is transient and morphology of erythrocytes is normal.

  • Pathological reticulocytosis

Results from increased in bone marrow production secondary to external or internal blood loss and hemolytic disease.

If the blood loss or destruction is greater than the rate of new blood cell production by the bone marrow, anemia will be present. If the rate of erythrocyte production matches or is greater than loss or destruction, the animal will not be anemic. Reticulocytosis can also occur with conditions that cause absolute erythrocytosis (polycythemia vera).

Causes of pathological reticulocytosis include splenectomy, immune-mediated hemolytic anemia[2][3], phosphofructokinase deficiency and Trypanosoma spp[4] and Babesia spp infections[5]


  1. Randolph JE et al (2004) Clinical efficacy and safety of recombinant canine erythropoietin in dogs with anemia of chronic renal failure and dogs with recombinant human erythropoietin-induced red cell aplasia. J Vet Intern Med 18(1):81-91
  2. Klag AR et al (1993) Idiopathic immune-mediated hemolytic anemia in dogs: 42 cases (1986-1990). J Am Vet Med Assoc 202(5):783-788
  3. Mason N et al (2003) Cyclophosphamide exerts no beneficial effect over prednisone alone in the initial treatment of acute immune-mediated hemolytic anemia in dogs: a randomized controlled clinical trial. J Vet Intern Med 17(2):206-212
  4. Egbe-Nwiyi TN & Antia RE (1993) The effect of trypanocidal drug treatment on the haematological changes in Trypanosoma brucei brucei infected splenectomised dogs. Vet Parasitol 50(1-2):23-33
  5. Hossain MA et al (2004) Inhibitory effect of pyrimidine and purine nucleotides on the multiplication of Babesia gibsoni: possible cause of low parasitemia and simultaneous reticulocytosis in canine babesiosis. J Vet Med Sci 66(4):389-395