Anemia:

• It may be defined as decrease in quantity of hemoglobin or number of erythrocytes or both per unit volume of blood.
• It is characterized clinically by pale mucus membrane, tachycardia and loss of muscular strength and vigour.

Classification of anemia:

Anemia are classified based on following categories;

1. According to morphology
2. According to response
3. According to etiology/patho-physiologic mechanism

Anemia according to morphology of red blood cells:

On the basis of morphology of red blood cells, anemia are of following types:

1. Macrocytic normochromic anemia:

• This type of anemia denotes the presence of immature red blood cells in blood.
• It occurs due to deficiency of vitamin B₁₂, folic acid, cobalt, intrinsic factors and erythrocyte maturation factors.
• Size of RBCs is increased in this type of anemia and bone marrow is responsive.

2. Macrocytic hypochromic anemia:

• This anemia occurs in regenerative phases after hemorrhage.
• Hemorrhage may be due to trauma, wound, surgical bleeding, parasitic oozing of blood, epistaxis, etc.
• Size of RBC is increased with decreased Hb concentration.

3. Normocytic normochromic anemia:

• This is known as aplastic or hypoplastic anemia.
• Staining properties of RBC’s are normal. Number of granulocytes and thrombocytes are reduced
• It occurs due to suppression of bone marrow activity in acute or sub-acute systemic disease.
• It may be primary or secondary. Primary is rare.
• Secondary anemia may occur due to:
  • Chronic hemorrhage
  • Neoplasm
  • Deficiency of vitamin-6 and prothrombin
  • Ionization and irradiation
  • Chemical poisoning
  • Bracken fern poisoning
  • Sulphonamide and chloramphenicol toxicity
• Size of RBC is normal with normal hemoglobin concentration.

4. Normocytic hypochromic anemia:

• This type of anemia occurs due to reduced hemoglobin formation.
• Size of R.B.C is normal with reduced hemoglobin concentration.
• This anemia occurs due to following factors/causes:
  • Dietary deficiency of iron; due to exclusive intake of milk in piglets or defective absorption of iron
  • Dietary deficiency of copper
  • Dietary deficiency of ascorbic acid (Vitamin-C)
  • Dietary deficiency of pyridoxine
  • Dietary deficiency of nicotinic acid
  • Dietary deficiency of riboflavin
  • Deficiency of thyroxine

5. Microcytic normochromic anemia:

• In this type of anemia, size of RBC is reduced with normal hemoglobin concentration
• This anemia occurs due to following causes:
  • Chemical poisoning
  • Chronic interstitial nephritis
  • Worm infection
  • Chronic infection like tuberculosis, brucellosis
  • Ionizing radiation

6. Microcytic hypochromic anemia:

• This anemia result due to deficiency of iron.
• It also occurs due to dietary deficiency of copper, manganese, cobalt, ascorbic acid, pyridoxine, nicotinic acid, riboflavin, thyroxin, etc.
• Size of RBCs are reduced with reduced hemoglobin concentration.

Anemia according to response:

1. Regenerative anemia:

• Bone marrow is responsive to this type of anemia.
• It is characterized by increased number of immature RBC in peripheral circulation
• Ex; blood loss anemia, hemolytic anemia

2. Non-regenerative anemia:

• Bone marrow is not responsive to anemic state.
• Bone marrow are unable to produce red blood cells.
• Ex; Depression anemias and aplastic anemias

Anemia according to etiology and pathophysiologic condition:

1. Haemorrhagic anemia:

• There is loss of RBCs in this type of anemia. Blood loss exceeds production.
• It occurs when 25-40% of blood is lost. This condition leads to hypochromic, microcytic anemia
• It may be acute or chronic in nature
• Acute haemorrhagic anemia occurs due to:
  • Any wound
  • Epistaxis
  • Hemoptysis
  • Surgical bleeding
  • Splenomegaly in dog
  • Brackern fern poisoning
  • Sweet clover poisoning
  • Rapid X-ray exposure
  • Gastrointestinal hemorrhage
  • Genito-urinary hemorrhage
• Chronic hemorrhagic anemia occurs due to:
  • Heavy ectoparasitic infestation
  • Endoparasitic infection
  • Deficiency of vit. K, vit.C and prothrombin
  • Coccidiosis in young animals
  • Enzootic bovine Hematuria

2. Hemolytic anemia:

• This type of anemia occurs due to accelerated erythrocyte destruction.
• It is characterized by macrocytic hypochromic anemia.
• It may be of 2 types; congenital hemolytic anemia and acquired hemolytic anemia
• Congenital anemia occurs due to defect in formation of stroma of protein or hemoglobin. It is heritable disease due to simple Mendelian recessive gene.
• Acquired hemolytic anemia occurs due to:
  • Viral infection: Equine infectious anemia, infectious mononucleosis
  • Bacterial infection: Leptospirosis, Clostridium haemolyticum, Clostridium perfringens type A, streptococcal and staphylococcal infection
  • Protozoal infection: Babesiosis in all species, Anaplasmosis in ruminants, theileriosis, haemobartonellosis in dog and cat
  • Phosphorus deficiency
  • Copper poisoning
  • Phenothiazine toxicity
  • Ingestion of arsenic, bismuth, lead
  • Excessive use of sulphonamides and other aspirin drug
  • Snake venom

3. Immunological haemolytic anemia:

• It is of 2 types; Autoimmune haemolytic anaemia and iso-immune haemolytic anemia
• Auto-immune hemolytic anemia:
  • It is recorded in dog and cat
  • Under special circumstances, there may be mutation of genes and protein of own body becomes antigen and body produced antibody against own erythrocytes.
  • Due to result of Ag-Ab reaction, hemolysis occurs
  • Disease is characterized by sudden onset of anemia and spherocytosis
• Iso-immune haemolytic anemia:
  • This anemia occurs due to transfer of maternal iso-antibodies from dam to new-born through colostrum.

4. Dyshaemopoetic anemia:

• This anemia results due to depression of erythropoiesis
• Certain chronic suppurative process may depress bone marrow activity leading to less production of erythrocytes.
• It may be observed in case of nephritis, chronic interstitial nephritis, neoplastic disease, rapid exposure to X-ray or other radioactive substances, drug toxicity, viral infection causing marrow suppression.

Clinical Signs:

• Paleness of visible mucus membrane
• Muscular weakness, dull and depression
• Inappetance to anorexia
• Tachycardia (increased heart rate)
• Decrease in intensity of heart sound in later stage
• Labored breathing at terminal stage due to anemic anoxia
• Signs of shock in hemorrhagic anemia
• Jaundice
• Hemoglobinuria, hematuria, edema

Laboratory findings:

• Reduction in number of RBC
• Reduction in amount of hemoglobin
• Morphological abnormalities in RBC

Diagnosis:

• Based on history, clinical findings and laboratory findings

Treatment:

• Attempt should be made to correct primary causes with appropriate measures
• In severe cases, whole blood transfusion is carried out.
• Plasma extender; haemacel may be used @ 10-15ml/kg, b.wt.
• Haematinic preparations may be used in less severe cases and as supportive treatment after transfusion.
• Iron preparation; ferrous sulphate are injected IV, gives rapid response. Ferrous sulphate, 4-8 g, 1 dose BID for 3 days
• Fersolate tablet @ 1-2 tab, BID for dog
• Imferon injection available in 2 ml ampule. Sig; 4 amps (6-8ml) at a time daily or alternate days according to severity through IM route
• Iron dextran @ 5-10 ml. I/M
• Liver extract; Belamyl injection, Livogen injection @ 5-10 ml in alternate days in case of severe anemia.
• Livogen syrup @ 1-2 t.s.f, BID, PO for small animals
• In case of immune mediated hemolytic anemia, glucocorticoid therapy is given. Prednisolone @ 1-2 mg/kg, PO, BID.
• Dexamethasone is given @0.3-0.5 mg/kg, IV, OD
• For immunosuppression in dogs and cats, azathioprine is used @ 2mg/kg, PO, OD. Cyclosporine can be used @ 5-10 mg/kg, b.wt., PO, BID