Equine Anemia

Question 1

What are the clinical signs of Blood Loss Anemia in horses?

Answer 1

Response to Hypoxia
- Tachycardia, tachypnea, weakness, depression, colic
- Signs depend on severity & duration

Hgb-O2 Dissociation Curve

Normal equine PCV = 28-45%

Question 2

What are the clinical signs of Hemolytic Anemia in horses (IV versus EV signs)?

Answer 2

IV: hemoglobinemia, hemoglobinuria, unconjugated biliruninemia

EV: Noral plasma and urine, unconjugated bilirubinemia

IV: Hgb released from duestruced RBCs into vasculature

Plasma in equines is normallly icteric-looking. -> spin down, RBC pellet and clear plasma = most likely EV hemolysis (no hemogolobinemia)

Question 3

What diagnostics are useful for working up an anemic horse?

Answer 3

• PCV/TS
• Horses do NOT have reticulocytes! –> Determine regeneration via evidence of macrocytosis via MCHC or smear
• Increased anisocytosis via RDW (RBC Redistribution Width)
• Bone marrow sampling (gold standard, but invasive)
• CBC
• Dipstick (determine pigmenturia)

Anisocytosis is normal in horses

Macrocytosis

Question 4

Pigmenturia: describe findings // how to differentiate
- Hematuria
- Hemoglobinuria
- Myoglobinuria

Answer 4

Hematuria: centrifuged whole RBCs form into pellet at bottom with clear urine above

Hemoglobinuria and Myoglobinuria: urine is not going to settle out after centriguging form the RBCs –> differentiate via hemoglobinemia (spun PCV tube has red plasma)

Hemoglobinuria

Question 5

What are the categories of causes of anemia?

Answer 5

1. Blood Loss
2. Hemolysis
3. Decreased Erythropoiesis

Question 6

IV versus EV Hemolysis pathogenesis

Answer 6

IV = RBCs being destructed within thesystemic vacsulature

EV = RBCs being destructed by phagocytosis outside the systemic vasculature (e.g., in the spleen, lymph nodes, etc.)

Question 7

Differentials for Blood Loss Anemia

Answer 7

Internal hemorrhage
- Hemothorax, hemoperitoneum, middle uterine artery rupture

External Hemorrhage
- Traumua (most common), epistaxis, Gi bleeding, hematuria

Question 8

How much blood volume can horses/all mammals lose before death?

Answer 8

30-33%
- BV = 8% of BW

500kg horse has 40L of blood in body –> can lose 13L (one bucket full)

Question 9

Indications to start blood transfusion acutely versus chronically presented anemia

Answer 9

PCV < 18% acutely
PCV < 12% chronically

LA don’t develop alloantibodies unless previously exposed (previous transmusion, pregnancy) –> usually we do NOT crossmatch blood type for horses!

Question 10

Red Maple Toxicity
- etiology
- pathogenesis + possible sequlae
- tx

Answer 10

Causes severe tissue hypoxia due to IV hemolytic anemia + methemoglobinemia
- possible sequelae: renal failure, colic, laminitis
- tx = blood transfusion, supportive care, ascorbic acid

Ascorbic acid: reduces methemoglobin to hemoglobin

Question 11

Equine Infectious Anemia
- pathogen / transmission
- diagnosis

Answer 11

• retrovirus transmitted on mouthparts of large biting flies (horse and deer flies)
• dx = Coggins Test (AGID) –> negative Coggins required within 1 year prior

Clinical Signs of EIA -> infection results in lifelong carrier state if horse survives acute phase.

Isolated from uninfected horses for life (they are lifelong carriers) and separated at a distance of at least 200 yards (max distance fly will travel).