Equine Haematological Disorders

Question 1

1. What tests and measurements can be run to assess quantity of erythrocytes in circulation?
2. Note for age with these measurements?

Answer 1

1. RBC count, Haemoglobin, PCV.
2. First weeks of life, these measurements decrease rapidly.

Question 2

1. Haemoglobin conc. in normal horse?
   – When would there be an increase?
2. What measurements can be taken from RBCs?
3. What is anisocytosis?
4. What are acanthocytes?
5. What is Rouleaux formation?
6. What is agglutination?

Answer 2

1. 1/3 PCV.
   – Intravascular haemolysis.
2. Mean Cell Volume, Mean cell haemoglobin conc., characterise anaemia, automated, calculate from RBC count and Hb and PCV.
3. More variation in the size of the RBCs than normal.
4. RBCs with spikes of varying sizes on the cell surface. They are associated with disease.
5. Where RBCs stack/group together. Normal.
6. The clumping together of RBCs associated with disease (antibody-antigen reaction).

Question 3

1. When would bone marrow aspirate for evaluation be indicated in the horse?
2. What could be done with the aspirate?
3. Method of taking bone marrow aspirate.

Answer 3

1. If suspect disorder of haematopoietic system but cannot diagnose it from routine lab tests. Rare.
2. Use to characterise anaemia.
   Evaluate iron stores.
   Explain quantitative or qualitative abnormalities of blood cells.
3. At the sternum, clip and scrub, use LA, make a skin incision, and use Jamshedi needle with pressure and routine to enter the bone. Smear the aspirate and fix with formalin.

Question 4

1. Why is iron deficiency rare?
2. What explains low iron levels in most cases?

Answer 4

1. Well managed horses eat green leafy vegetable all day and should obtain enough iron via this.
2. Disturbances of iron metabolism so anaemia of chronic disease.

Question 5

1. What is erythrocytosis?
2. Effect on the blood?
3. Consequence of this for animal?

Answer 5

1. Increased RBCs.
2. Increased viscosity.
3. Tissue hypoxia, thrombosis, haemorrhage, weakness, lethargy, exercise intolerance.

Question 6

In what cases would you get relative erythrocytosis?

Answer 6

Splenic contraction:
- due to excitement / stress.
- recover after a few hours.
Loss of plasma volume w/o change in RBC numbers:
- dehydration, endotoxic shock.

Question 7

In what cases would you get absolute erythrocytosis?

Answer 7

Primary:
- Rare myeloproliferative disorder (cancer).
Secondary, appropriate:
- Response to tissue hypoxia e.g. cardiac anomalies.
Secondary, inappropriate:
- Increased erythropoietin release w/o hypoxia.
- Usually neoplasia.

Question 8

1. Measurements to indicate anaemia.
2. Range of clinical signs.

Answer 8

1. Decreased PCV, RBC count.
   And decrease in Hb, unless intravascular haemolysis.
2. None/mild to severe hypoxia.

Question 9

1. Haematological causes of anaemia (basic).
2. How could you tell if the anaemia was regenerative or non-regenerative?

Answer 9

1. • Increased loss of RBCs.
     - Increased destruction of RBCs.
     - Decreased production of RBCs.
2. Based on bone marrow response.
   MCV.
   MCHC.

Question 10

1. Where there is internal haemorrhage, what can be done to restore losses?
2. Clinical signs of haemorrhage?

Answer 10

1. Autotransfusion.
2. Vary dept. on duration and severity of blood loss.
   Can lose up to 1/3 (10-12L) blood volume.
   Severe clinical signs at PCV 12-20%.
   In acute blood loss, PCV drop hidden initially, and protein drops too.

Question 11

1. Clinical signs of hypovolaemic shock.
2. Recovery from haemorrhage.

Answer 11

1. Tachycardia.
   Pale MMs.
   Weakness.
   Oliguria.
2. PCV can increase by <1% per day but this is greater if blood loss is internal.

Question 12

Treatment of haemorrhage.

Answer 12

Identify and stop source of bleeding.
Can us Tranexamic/aminocaproic acid.
Isotonic fluids (could increase BP and increase haemorrhage but equally need to replace losses so treat as case-by-case.
Colloids (same goes as isotonic fluids).
Oxyglobin is expensive!
NOT hypertonic saline!

Question 13

1. Types of haemolysis and measurements that show this and consequences of one.

Answer 13

1. Intravascular
   - Haemoglobinaemia (increased MCHC).
   - Haemoglobinuria.
   - Consequences: nephrotoxic and can lead to renal failure.
   Extravascular.

Question 14

1. What does IMHA stand for?
2. How common is IMHA in horses?
3. What does IMHA do?
4. Where is IMHA more common in horses?
   – cause?
5. Most IMHA intravascular or extravascular?

Answer 14

1. Immune Mediated Haemolytic Anaemia.
2. Uncommon.
3. Production of antibodies that attach to surface of RBCs and destroy them.
4. When it is secondary.
   – caused by alterations to RBC membrane by viral/bacterial/neoplastic disease. Can also be drug-induced (often antigen-antibody complex deposition). –> penicillin, TMPS.
5. Extravascular.

Question 15

1. IMHA clinical signs.
2. Diagnosis of IMHA.

Answer 15

1. Insidious, fever, lethargy, weight loss.
2. Decreased RBC count.
   Spherocytes.
   Increased MCV.
   Anisocytosis.
   Increased total and indirect bilirubin.
   Haemoglobinaemia.
   Autoagglutination.
   Coomb’s test.

Question 16

Treatment of IMHA in horses.

Answer 16

• Identify underlying cause?
• Discontinue previously administered drug.
  – Treat underlying disease.
• If severe, blood transfusion.
• If haemoglobinuria, IV fluids as risk of nephropathy.
• Corticosteroids.
  prognosis depends on cause

Question 17

1. What does EIAV stand for?
2. Where is it endemic?
3. Where is found?
4. What is the basic mechanism of anaemia with EIAV?

Answer 17

1. Equine Infectious Anaemia Virus.
2. Parts of Europe and USA.
3. Sporadic cases in UK.
4. Haemolysis.

Question 18

What are the clinical syndromes of EIAV?

Answer 18

• Acute infection.
• Chronic infection.
• Inapparent carrier.

Question 19

1. Clinical signs of Acute EIAV?
2. Why is acute EIAV difficult to diagnose?
3. What tests can be run for diagnosis of acute EIAV?

Answer 19

1. Fever, lethargy, anorexia, thrombocytopenia.
2. Can take 40 days to seroconvert.
3. AGID (Agar Gel Immnodiffusion Assay) / Coggins / C-ELISA.

Question 20

1. Clinical signs of chronic EIAV infection.
2. How is chronic EIAV infection easier to diagnose?
3. How can an inapparent carrier be identified?

Answer 20

1. Recurrent fever, weight loss, ventral oedema, anaemia.
2. Seropositive.
3. They will be seropositive.

Question 21

1. How is EIAV transmitted?
2. Why is slaughter often required for animals that are infected? – compensation?

Answer 21

1. Blood-sucking insects.
   Mare to foal across placenta, via colostrum and milk.
   Aerosol?
   Iatrogenic – blood product transfusions or blood-contaminated instruments.
2. Notifiable disease – £1 compensation.

Question 22

1. How are horses infected with babesia?
2. Why would babesia be relevant to us?

Answer 22

1. Ticks.
2. If horse has travelled.

Question 23

1. What is non-regenerative anaemia basically caused by?
2. What can cause this?

Answer 23

1. Suppression of bone marrow erythropoiesis.
2. Chronic disease w/ disturbance of iron metabolism.
   Iron deficiency usually due to chronic blood loss.
   Endocrine disease.
   Neoplastic disease.

Question 24

Most common cause of anaemia in the horse?

Answer 24

Chronic disease and using thoroughbred reference range.

Question 25

1. What is haematopoietic neoplasia? 2. When is this classified as leukaemia? -- common? 3. Types of haematopoietic neoplasia?

Answer 25

1. Uncontrolled proliferation of 1 or more marrow-derived blood cell lines. 2. When neoplastic cells are seen in peripheral circulation. -- rare. 3. Myeloid and lymphoid.

Question 26

Clinical signs of myeloid neoplasia.

Answer 26

Depression. Weight loss. Fever. Oedema. Petechial haemorrhage. Anaemia.

Question 27

1. Diagnosis of myeloid neoplasia in horses. 2. Treatment? 3. Prognosis?

Answer 27

1. Peripheral blood smear. Bone marrow aspirate. 2. No treatment found. 3. Survive a few weeks.

Question 28

1. Locations of lymphoid neoplasia in horses? 2. Age affected? 3. Clinical and lab changes from loss of organ function caused by?

Answer 28

1. Generalised, intestinal, mediastinal, cutaneous. 2. 5-10yrs. 3. Infiltration of lymphocytes. Physical obstruction by tumour masses. Tumour cell cytokines.

Question 29

Clinical signs of lymphoid neoplasia in horses?

Answer 29

Vary w/ location. Often chronic disease w/ sudden onset of more severe signs. Weight loss. Fever. Ventral oedema. Paraneoplastic syndromes.

Question 30

Diagnosis of lymphoid neoplasia in horses.

Answer 30

Demonstration of neoplastic lymphocytes in affected tissue. Biopsy mass. - If intestinal: -- rectal biopsy. -- Abdominoparacentesis. -- Laparoscopy. -- Laparotomy.

Question 31

Treatment of lymphoid neoplasia in horses.

Answer 31

Usually present in advanced stage of disease. Could resect tumour, give chemotherapy, give radiotherapy. -- v expensive. -- Can achieve remission for 12-18mths. Usually euthanise.

Question 32

1. Clinical signs of thrombocytopenia? 2. Mechanisms of thrombocytopenia.

Answer 32

1. Abnormal primary haemostasis. Epistaxis. Petechial haemorrhage. 2. - Decreased platelet production via bone marrow suppression. - Increased platelet destruction via IMTP or Equine Infectious Anaemia. - Abnormal platelet function.

Question 33

1. What happens in primary haemostasis? 2. What happens in secondary haemostasis? 3. Clinical signs of disorders of haemostasis.

Answer 33

1. Platelets plug vascular defect. 2. Interaction of coagulation factors to form a fibrin mesh. Extrinsic, intrinsic, common pathways. 3. - Abnormalities of primary haemostasis. - Abnormalities of secondary haemostasis w/ spontaneous or excessive haemorrhage in response to surgery or trauma.

Question 34

Diagnosis of disorders of haemostasis.

Answer 34

- Whole blood clotting time. - Platelet count on smear. - Buccal mucosal bleeding. - Activated clotting time. -- Time to clot formation on activation of whole blood. -- Evaluates deficiencies of Factor VIII and IX, prothrombin, fibrinogen. -- Not altered by abnormalities of Factor VII and platelets. - APTT (activated partial thromboplastin time) -- Measure activity of factors V, VIII, IX, X, XI, XII. -- APTT more reliable than PTT in horses. - PT -- Extrinsic and common coagulation pathways. - FDPs, D-Dimer, TEG clotting (good -- hospital based). - Specialised assays for components of cascade.

Question 35

1. Hereditary disorders of haemostasis. 2. Acquired disorders of haemostasis.

Answer 35

1. Von Willebrand's disease. Factors VIII deficiency. 2. - Vasculitis from infectious diseases or immunologic diseases. - Disseminated Intravascular Coagulation.

Question 36

1. What is thrombophlebitis? 2. When is the risk of this increased? 3. Important precaution? 4. Treatment of thrombophlebitis? 5. Risks associated with thrombophlebitis?

Answer 36

1. (Infected) thrombus at a site of endothelial damage -- usually catheter site. 2. Sepsis, endotoxaemia, DIC. 3. Aseptic technique for catheter placement and monitor catheter, replacing when necessary. 4. Hot pack. Topical treatment. Systemic antibiotics if necessary. Aspirin. 5. Bilateral thrombophlebitis. Endocarditis.

Question 37

1. When is blood transfusion necessary? 2. Signs of tissue hypoxia.

Answer 37

1. If anaemia severe enough to impair tissue oxygenation. 2. - Tachycardia. - Tachypnoea. - Lethargy. - Weakness. - Cool extremities. - Pale MMs.

Question 38

1. When may blood transfusion be indicated? 2. How are signs less obvious with chronic anaemia? 3. How does blood donation work?

Answer 38

1. - At PCV of10%-18% depending on rapidity of erythrocyte loss. - Severe haemorrhage with DIC to renew supplies of coagulation factors and platelets. 2. It allows for physiological adaptation. 3. Blood has to be collected for a patient, not able to store it, unless patient then does not need it, then can be stored in a fridge. Some hospitals have blood donors. Ideally perform major and minor cross match. Can do this before a planned major surgery.

Question 39

Blood transfusion for the critical patient.

Answer 39

No time to cross match. Usually fine even to have multiple transfusion for the first 3-4 days. Chances of an adverse reaction increase when either donors or recipients are mares that have been bred previously.

Question 40

Method of blood transfusion.

Answer 40

Usually safe to remove 5-10L from donor. Sterile. Catheter pointing up. Commercial collection bags. Transfuse slowly -- monitor HR, RR, TEMP. stop if reaction, supportive care. Volume required can be calculate w/ equation.

Question 41

1. What is the major sign of how a horse is coping w/ blood loss.

Answer 41

1. HR.