VT 121 Hematologic & Immunologic Diseases PowerPoint

Hematologic & Immunologic Diseases

Lesson Objectives

  • After this lesson, students will be able to:
    • List hematologic and immunologic diseases.
    • Understand associated diagnostics.
    • Discuss treatments for these diseases.

Terminology - Abbreviations

  • CBC: Complete Blood Count
  • WBC: White Blood Cell
  • PMN: Polymorphonucleocyte
  • Hct: Hematocrit
  • Hb: Hemoglobin
  • MCV: Mean Corpuscular Volume
  • MCH: Mean Corpuscular Hemoglobin
  • MCHC: Mean Corpuscular Hemoglobin Concentration
  • NRBC: Nucleated Red Blood Cell
  • EDTA: Ethylenediamine Tetra-Acetic Acid

Root Words

  • Erythr/o: Red
  • Leuk/o: White
  • Thromb/o: Clot
  • Poikil/o: Irregular
  • Acanth/o: Spiny

Review of Red Blood Cells

  • Red blood cells (RBCs) primarily carry oxygen from the lungs to cells and remove carbon dioxide and waste products.
  • Lifespan of RBCs is approximately 120 days; they are filtered out of circulation by macrophages in the spleen and liver post-life span.
  • Bone marrow consistently produces new RBCs to maintain proper blood counts.

Diagnostics for Hematologic & Immunologic Diseases

  • Packed Cell Volume (PCV): Measures the proportion of blood composed of red blood cells; expressed as a percentage.
  • Complete Blood Count (CBC): Provides information about the concentrations and various characteristics of red blood cells, white blood cells, and platelets.
  • Blood Smear: Used to identify red blood cell parasites, abnormal cells indicating conditions like leukemia, or other signs of damage.
  • Bone Marrow Aspirate:
    • Performed under sedation or anesthesia to assist in diagnosing bone marrow diseases.
    • Red marrow persists in the sternum throughout life.
    • Samples commonly collected from humerus, femur, or pelvis bones.
  • Blood Chemistries and Urinalysis (UA): Evaluates organ function, electrolyte levels, and overall health; can indicate kidney disease affecting bone marrow.
  • Fecal Exam: Checks for intestinal parasites that may cause blood loss (e.g., hookworms).
  • Imaging Techniques: Utilize radiographs and ultrasound to check for metastatic diseases or underlying issues.
  • FeLV/FIV Testing: Uses specific tests to detect feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV); can be done in-house or sent to reference laboratories.
  • Tick Testing: Some tick-borne diseases tested in-house using SNAP tests; others require serology or PCR tests in reference labs.

Erythrocyte Disorders

  • Categories:
    1. Inappropriate Loss (e.g., hemorrhage)
    2. Decreased Production (e.g., iron deficiency)
    3. Increased Destruction (e.g., hemolysis, related to conditions such as IMHA, mycoplasma haemofelis, and Heinz body anemia).
Diagnosing Anemia
  • Low packed cell volume (PCV) or hematocrit (Hct) indicates anemia:
    • Normal PCV/Hct values: Dog 36%-64%, Cat 26%-46%.
Types of Anemia
  • Regenerative Anemia: Characterized by reticulocytes being present; indicates bone marrow response.
  • Non-Regenerative Anemia: No reticulocytes present; could be pre-regenerative anemia if the marrow has not yet responded to acute blood loss.
Erythrocyte Disorders – Inappropriate Loss (Category 1)
  • Causes: Trauma, rat bait ingestion, coagulopathies, or severe internal bleeding.
  • Management: Focus on volume replenishment through crystalloid fluids, RBC replacement via transfusion, and addressing the source of blood loss.
Erythrocyte Disorders – Decreased Production (Category 2)
  • Causes: Chronic blood loss, severe flea infestations, gastrointestinal parasites, ulcers, or bleeding neoplasia.
  • Consequences: Results in microcytic (small) and hypochromic (low hemoglobin) RBCs.
  • Management: Treat the underlying causes, supplemented iron (for 30-60 days), and once parasites are eliminated, the body can restore RBC supply.
Erythrocyte Disorders – Hemolysis (Category 3)
  • Mechanism: Altered RBC membranes may be perceived as invaders, leading to macrophages removing these altered cells, causing hemolysis.
  • Common Symptoms: Exercise intolerance, pale mucous membranes, tachycardia, and possibly icterus (jaundice) in severe cases.
  • Management: Immunosuppressive therapy to curb the body’s response, possibly necessitating blood transfusions if the PCV drops too low.
Blood-borne Parasites and Erythrocyte Disorders
  • Mycoplasma Haemofelis: Common blood parasite causing feline anemia; adheres to RBCs and leads to their destruction.
  • Transmission: Through blood-sucking parasites, maternal transmission, or blood-sucking wounds.
  • Other Parasites: Include Babesia canis, Babesia gibsoni, and Cytauxzoon felix.
  • Clinical Signs: Weight loss, anorexia, fever, hepatomegaly, splenomegaly, dehydration, icterus.
  • Diagnosis and Treatment: Identification on blood smear; PCR or serology for specific pathogens; antibiotics (e.g., tetracycline, doxycycline) and supportive care are needed.
Toxin-Induced and Heinz Body Anemias
  • Heinz bodies: Dense round granules around red cells, visible when stained with new methylene blue.
  • Toxins: Onions, acetaminophen (Tylenol), and zinc can induce these types of anemia.
  • Clinical Manifestations: Sudden weakness, decreased appetite, reddish-brown urine, pale mucous membranes.
  • Diagnosis: CBC to identify anemia and blood smear for Heinz bodies; additional supportive treatments may be needed if anemia is severe.
Immune-Mediated Hemolytic Anemia (IMHA)
  • Mechanism: Immune system mistakenly targets RBCs due to antibodies on their membranes.
  • Types:
    • Primary: Without underlying causes, more common in breeds like Cocker Spaniels, Springer Spaniels, and Poodles.
    • Secondary: Triggered by underlying conditions, medications, or infections, notably more in cats.
  • Symptoms: Anorexia, weakness, fever, tachycardia, potential icterus, hemoglobin in urine.
  • Diagnosis: CBC for anemia and inflammatory response; blood smear for identifying spherocytes or ghost cells; possibly Coombs test for antibodies attached to RBCs.
  • Treatment: Glucocorticoids with additional immunosuppressants, GI protectants, blood transfusions if necessary. Prognosis is poor, with a 30-40% mortality rate despite aggressive treatment.

Thrombocyte Disorders

Immune-Mediated Thrombocytopenia (IMTP or ITP)
  • Mechanism: Antibodies code platelets for destruction, leading to low platelet counts and associated bleeding risks.
  • Clinical Demographics: Most common in middle-aged females, notably cocker spaniels. Commonly seen in cases presenting with epistaxis (nosebleeds).
  • Clinical Signs: Petechiae, ecchymosis, bleeding from gums, weakness, fever.
  • Diagnosis: CBC shows low platelet counts; imaging tests may reveal associated conditions.
  • Treatment: Similar immunosuppressive approach as with hemolytic anemia; prognosis tends to be guarded, with some patients requiring transfusions when severe.
Disseminated Intravascular Coagulation (DIC)
  • Overview: Serious condition often referred to as “Death is Coming!”
  • Causes: Blood transfusion reactions, cancers (certain leukemias), pancreatitis, some infections, liver disease, pregnancy complications, recent surgeries or anesthesia.
  • Manifests: Many clots leading to bleeding into tissues; usually results in euthanasia.
Warfarin/Brodifacoum Toxicity
  • Mechanism: Rodenticide that disrupts vitamin K dependent clotting factors, leading to bleeding disorders.
  • Symptoms: Internal bleeding due to lack of functional clotting factors.

Leukocyte Disorder

Leukocytes Overview
  • Five Types:
    • Granulocytes: Neutrophils, basophils, eosinophils.
    • Agranulocytes: T-lymphocytes, B-lymphocytes, monocytes.
Ehrlichiosis
  • Description: Infects white blood cells, seen predominantly in tropical and subtropical environments, particularly in southeastern and southwestern United States.
  • Transmission: Spread by Brown Dog Tick, causing endothelial damage, consumption of platelets, RBC destruction, and potential bone marrow suppression resulting in aplastic anemia.
  • Clinical Signs: Vary from acute phases (depression, anorexia, fever, weight loss, nasal discharge) to chronic phases (severe weight loss, bleeding, eye issues).
  • Diagnosis: Pancytopenia, thrombocytopenia, anemia; diagnosis confirmed via blood smear and possible IFA test.
  • Treatment: Typically with tetracycline or doxycycline.
Feline Lymphoma
  • Definition: Cancer of lymphocytes, often secondary to infections like FeLV. Common types include:
    • Intestinal Lymphoma: Thickening of intestine walls and lymph node enlargement, often in older cats.
    • Mediastinal Lymphoma: Associated with FeLV, presenting in younger cats with respiratory difficulties.
    • Renal Lymphoma: Can lead to renal failure.
  • Diagnosis: Cytology/histopathology of tissues, blood work, imaging, and FeLV/FIV testing.
  • Treatment: Primarily chemotherapy, sometimes supplemented with surgery/radiation and prednisone for palliative care.
Canine Lymphoma
  • Definition: More common in older dogs, classified similarly into multiple types, including multicentric, alimentary, mediastinal, and extranodal lymphomas.
  • Diagnosis: Cytology, biopsy, flow cytometry, and serology to classify the lymphoma type and staging.
  • Treatment: Chemotherapy, radiation, or surgical options for localized cases; palliative care involving prednisone.
Feline Immunodeficiency Virus (FIV)
  • Transmission: Bite wounds, blood transfusions, in utero, and lactation. Once infected, cats remain infected for life.
  • Clinical Signs: Asymptomatic initially, leading to signs of opportunistic infections upon immune system deterioration. Symptoms may include weight loss, poor appetite, fever, conjunctivitis, and non-healing wounds.
  • Testing: ELISA, Western blot, and PCR tests for virus identification; management of secondary infections typically required.

Clotting Disorders and Diseases

Types of Hemorrhages
  • Bruise (Contusion): A non-broken skin injury with blood effusion.
  • Petechia: Small, pinpoint hemorrhagic spots.
  • Ecchymosis: Larger irregular formed hemorrhagic areas; color changes over time.
  • Purpura: Red to purplish skin hemorrhages that undergo color transitions.
History and Clinical Signs in Clotting Disorders
  • Important History: First bleeding episode, previous surgeries, vaccinations, medications, rodenticides exposure.
  • Clinical Signs: Symptoms can include petechiae, hematomas, bleeding from mucous membranes, bleeding into body cavities, and prolonged clotting times.
Tests and Management in Clotting Disorders
  • Coagulation Tests: Overview includes platelet estimations, PT, PTT, BMBT, and clot tests.
  • Management Strategies: Minimizing trauma, careful use of needles, applying pressure post-venipuncture, minimal invasive procedures, and transfusions as needed.
Von Willebrand Disease (vWD)
  • Definition: Most common inherited clotting disorder characterized by reduced von Willebrand factor causing bleeding.
  • Prevalence: Commonly found in breeds like Dobermans and German Shepherds.
  • Genetics: Autosomal dominant trait, incomplete penetrance; breeding is discouraged if carrying the gene.
  • Treatment: Approaches may include plasma or cryoprecipitate infusions and desmopressin acetate before surgical procedures.

Immunologic Tests

Overview of Tests
  • SNAP Tests: Common in-house tests that measure either IgG or antigen presence. Positive results indicate either past exposure or current infection but not timing or differentiation.
  • Antibody Titers: Measures plasma IgG levels for effective immune response tracking.
  • Paired Antibody Titers: Baseline taken then a follow-up to measure increases, indicating active immune response initiation.

The Immune System Overview

  • Immunodeficiencies: Represent inadequacies in immune function, whether from developmental failures, old age susceptibility, or viral inhibition.
  • Hypersensitivity Reactions: May occur as overactive immune responses manifesting via varying severity.
  • Autoimmune Diseases: Conditions arise when the immune system targets self-tissues (e.g., diabetes type I, Addison’s disease, autoimmune thyroiditis).
Immunotherapy
  • Immunosuppressive Therapy: Involves corticosteroids and related drugs, intended to mitigate immune responses during hypersensitivity or autoimmune conditions; however, such treatments can raise vulnerability to infections.
  • Immunostimulant Therapies: Designed to enhance immune response, including standard vaccines and certain natural immunomodulators.