Equine Anemia

Question 1

What is Anemia?

Answer 1

• ​Decrease in circulating RBC mass
  
  • Decreased Pack Cell Volume
  • Decreased RBC
  • Hemoglobin decreased except with intravascular hemolysis

Question 2

What sites for Bone Marrow Biopsy are used in horses?

Answer 2

• Rib
• Sternum

Question 3

What are the (broad) causes for anemia?

Answer 3

• Blood loss
• Destruction/Hemolysis
• Decreased Production

Question 4

How is Regenerative vs. Non-regenerative anemia determined in horses?

Answer 4

• Horses do NOT release immature RBC into peripheral circulation
• May see a mild increase in anisocytosis and MCV
• Only way to determine Regenerative is w/ bone marrow biopsy
  
  • or wait 3 days to see if RBC# increases

Question 5

How can Internal hemorrhage and external hemorrhage be differentiated (I.e. GI bleed into lumen vs hemothorax)

Answer 5

• Internal: bleeding into the body cavity, ~⅔ of RBCs are autotransfused back into circulation w/in 24-72hrs
  
  • rest are phagocytized back - iron is reused
• External: blood is lost to outside, iron is lost

Question 6

What are the clinical signs of Blood Loss Anemia?

Answer 6

• Increase in HR & RR
• Pale mucous membranes
• poor venous distention
• weakness
• fainting
• Frequently have heart murmur
  
  • changes in blood viscosity

Question 7

How is Blood loss Anemia diagnosed?

Answer 7

• PCV and TP initially normal
  
  • Start reduction by 4-6hrs, takes up to 24hr for complete redistribution
• Splenic Contraction - adds RBC to peripheral blood
• Regeneration of RBC should start to be evident at 3 days, max response in 7 days
• PCV will increase about 1% or less a day

Question 8

What is the treatment for Blood loss anemia?

Answer 8

• Stop the bleed
  
  • surgical hemostasis
  • aminocaproic acid
  • Yunnan Baiyo
  • Formalin
• IV fluids - for severe acute hemorrhage - restore ‘volume’
• Blood transfusion -
  
  • signs of shock (PCV from 18% to 12% depends on speed of bleed)
    
    • Acute < 15-18%
    • Chronic <12%

Question 9

What is Blood transfusion crossmatching?

Answer 9

• Major cross match: compatibility between donor RBC and any alloantibody in patient’s plasma
• Minor cross match: compatibility between alloantibody in donor’s plasma and patients RBC

Question 10

What is a ‘universal donor’ for equine blood transfusions

Answer 10

• Donors that do not have Aa or Qa blood types
  
  • also lack Aa or Qa antibodies in plasma

Question 11

What are the clinical signs of Chronic Blood loss?

Answer 11

• Animals will tolerate a much lower PCV than with acute blood loss
• Weight loss
• ill thrift
• pale mucous membranes
• heart murmur (viscosity related)
• exercise intolerance
• signs of shock if severe enough

Question 12

How is chronic blood loss diagnosed?

Answer 12

• Find source of blood loss

Question 13

What is the treatment for chronic blood loss?

Answer 13

• stop bleeding
• supplement with dietary iron if necessary

Question 14

what causes Chronic Blood loss?

Answer 14

• Immune mediated destruction
• Oxidative injury to the RBC
• Infectious agents
  
  • may increase RBC fragility
  • may induce IMHA
• Iatrogenic
  
  • hypo or hypertonic drugs
• Liver or Renal hemolysis

Question 15

How can intravascular hemolysis and extravascular hemolysis be differentiated?

Answer 15

• Intra:
  
  • Hemoglobinemia (pink plasma)
  • icterus
  • hemoglobinuria (red/brown urine)
• Extra:
  
  • intense icterus

Question 16

What is Immune Mediated Hemolytic Anemia? (IMHA)

Answer 16

• Antibodies to RBC

Question 17

What are the clinical signs of IMHA in Horses?

Answer 17

• Depend on intra/extravascular hemolysis
• Fever

Question 18

What bloodwork is common in horses with IMHA?

Answer 18

• Anemia
• +/- pink plasma (intravascular hemorrhage)
• ⇡ total & indirect bilirubin

Question 19

how is IMHA diagnosed?

Answer 19

• Detection of antibody on RBC
  
  • Coomb’s test
  • Direct immunofluorescence/Flow cytometry
    
    • IgG, IgA, IgM
  • Autoagglutination

Question 20

What causes false negatives on a Coomb’s test?

Answer 20

• Use of steroid prior to testing
• rapid hemolysis of RBC that have antibody on them

Question 21

What causes IMHA in horses?

Answer 21

• Drugs - penicillin
• Infectious agents
  
  • equine infectious anemia
  • streptococcal
  • clostridial infections
  • Piroplasmosis
• Neoplasia - lymphosarcoma
• Maternal antibody - neonatal isoerythrolysis
• Idiopathic IMHA

Question 22

What is the treatment for IMHA in horses?

Answer 22

• Stop all previously administered drugs
• remove/treat underlying disease
• immunosuppression (steroids)
• blood transfusions (if necessary - concern for reactions)
• prevention of hemoglobin induced nephrotoxicity (use of fluids)

Question 23

What does oxidative injury do to RBCs?

Answer 23

• Heinz body formation
  
  • oxidized, precipitated hemogglobin
  • appear as round, blue-black granules on RBC membrane
    
    • can see w/ New Methylene Blue stain
  • Result in damage to RBC membrane → Invtravascular hemolysis
• methemoglobinemia
  
  • heme iron oxidized from ferrous to ferric
  • Can’t carry oxygen
  • Mucus membranes will appear brown

Question 24

What causes Oxidative injuries to RBCs in horses?

Answer 24

• Wilted Red Maple leaves (Acer rubrum)
• Wild onions - n-propyl disulfide
• phenothiazines
• Nitrate poisoning - methemoglobin only → no intravascular hemolysis

Question 25

What are the clinical signs of Red Maple toxicosis?

Answer 25

* Rapid death * several days of hemoglobinuria * brown mucus membranes * high heart rate

Question 26

How is Oxidative RBC injury diagnosed?

Answer 26

* Rule out IMHA * look for Heinz bodies * Methemoglobinemia (normal \<1.77%) * Red Maple can cause up to 50%

Question 27

How is RBC Oxidative Injury treated?

Answer 27

* Blood transfusions may be necessary * fluids to prevent hemoglobin-induced nephrotoxicity * Large doses of Vit C * Supportive Care

Question 28

What causes Nonregenerative Anemia in horses?

Answer 28

* Anemia of chronic disease - common (mild anemia) * Iron deficiency - uncommon * Bone Marrow Suppression - rare * drugs or neoplasia

Question 29

What does Anemia of Chronic disease look like? (on blood smear)

Answer 29

* Mild to moderate anemia * Normocytic * normochromic * non-regenerative * Does NOT result in clinical signs * treatment not necessary

Question 30

What is the pathophysiology of Anemia of Chronic Disease?

Answer 30

* Basic cause - **lack of iron mobilization** * inflammation results in increased production of hepcidin (protein from the liver) * ⇡Hepcidin → ⇣Ferroportin → iron trapped intracellularly (not available for RBC production)

Question 31

What is Ferroportin? purpose?

Answer 31

* Transmembrane protein present on enterocytes, macrophages, liver cells * Transports iron out of the cell

Question 32

How is Anemia of Chronic Disease Diagnosed?

Answer 32

* Mild anemia and chronic disease * Bone Marrow - document non-regenerative anemia * Serum iron conc. ⇣ * indices of iron storage are normal

Question 33

What is Iron deficiency? what does it look like on blood smear? causes?

Answer 33

* Uncommon * Serum iron concentrations decreased * indices of iron storage also decreased (ferritin, bone marrow staining for iron) * Blood Smear: * non-regenerative * microcytic * hypochromic * Cause: chronic external blood loss

Question 34

What causes Bone Marrow Suppression in horses?

Answer 34

* Drugs: * recombinant human erythropoietin * autoantibodies that cross react with equine erythropoietin * SMZ (pancytopenia) * Neoplasia - myelophthisis * accumulation of abnormal cells in bone marrow * Viral - Equine Infectious Anemia * Chronic Renal Failure * lack of erythropoietin production

Question 35

What is Hepcidin?

Answer 35

* Antimicrobial peptide * Produced in the liver secondary to inflammation * Destroys ferroportin