Anemia, Thrombocytes, and Blood Parasites

1. Anemia, Thrombocytes, and Blood Parasites Clinical Pathology

2. Autoimmune Hemolytic Anemia (AIHA) • Antibodies directed against RBC membrane antigens and Ab- coated RBC’s are removed from circulation. • Hemolytic process results in varying degrees of anemia depending on antibody type, speed of development, and duration of the disease process. • Female dogs are more commonly affected than males. • Certain breed predispositions include: Poodles, Cocker Spaniels, Terriers, Old English Sheepdogs, Lhasa Apsos, and Shih Tzus. • Rare in cats, usually associated with FeLv or Hemobartonella.

3. AIHA continued • The spleen is the primary site for removal of RBC’s coated with IgG while the liver removes RBC’s coated with IgM. • Onset of anemia may be acute or gradual. • Complications: • DIC • Pulmonary Thromboembolism

4. Causes of AIHA • Primary AIHA: autoantibodies directed against RBC’s with no underlying disorder, most common. • May occur in association with immune mediated thrombocytopenia. • Secondary AIHA: Ab production initiated by drugs, vaccines, infectious diseases and neoplastic disorders.

5. Diagnosis • History and Physical Exam • CBC • Regeneration • Spherocytes • Autoagglutination • Anemia (PCV<20%) • Coombs Test • Splenomegaly and Hepatomegaly seen on radiographs.

7. Therapy for AIHA • Corticosteriods: • Reduces clearance of Ab coated RBC’s by inhibiting function of macrophages in the spleen and liver. • Prednisone at dose of 2 mg/kg/day divided BID. • Blood transfusions in life-threatening situations. • Other immunosuppressive drugs • Cyclophosamide • Azathioprine • Cyclosporine • Splenectomy • Indicated if anemia is nonresponsive to immunosuppressive drugs.

8. Classification of Nonregenerative Anemia • Primary failure of erythropoiesis • Secondary failure of erythropoiesis • Nuclear maturation defects • Hemoglobin synthesis defects • Aplastic anemia • Marrow infiltration

9. Primary Failure of Erythropoiesis • Patient stops producing red blood cells • Circulating blood has few reticulocytes, normocytic, normochromatic RBC’s. • Bone marrow normal except for hypoplasia of erythroblasts. • May be immune-related or caused by certain drugs or neoplasia.

11. Secondary Failure of Erythropoiesis • Caused by a chronic disorder such as renal failure, liver disease, inflammatory disease, neoplasia, and endocrine disorders. • Bone marrow is normal or has slight erythroid hypoplasia.

12. Nuclear Maturation Defects • Associated with folate and B12 deficiency (rare). • Macrocytic, normochromic anemia due to a defect in DNA synthesis. • Megablastic erythroblasts in bone marrow. • Check serum folate and supplementation is the cure.

13. Hemoglobin Synthesis Defect • Primary associated with iron deficiency. • Microcytic, hypochromic anemia due to decrease Hb production in individual cells. • Iron deficiency can result from a poor diet, poor absorption, and following an incident of marked blood loss.

14. Aplastic Anemia • Bone marrow failure due to marrow necrosis and/or inflammation. • Bone marrow is acellular or hypocellular resulting in anemia, thrombocytopenia, and leukopenia. • Causes: • Ehrlichia canis • FeLv • Parvovirus • Estrogen • Phenylbutazone • Radiation • Chemotherapy

16. Marrow Infiltration • Neoplasia: crowding of marrow elements with neoplastic cells. • Myelofibrosis: hypoplasia of marrow elements with replacement by collagen (sequel to damaged marrow). • Osteopetrosis: inherited disorder with increased bone density.

17. Thrombocyte = Platelets • Platelets are produced by fragmentation of megakaryocytes in bone marrow • 150-200 platelets are formed from one megakaryocyte. • Lifespan: 7-10 days • Normal count: 200,000 – 500,000/mm3 • Thrombocytopenia- most common cause of bleeding in dogs. • Normal hemostatis depends on adequate platelet number and function • Important role in primary hemostatis involving interaction between injured blood vessel wall and platelets

18. When Thrombocytopenia is found • Make sure you had a good stick, if not recollect sample from a large peripheral vein. • If yes, perform coagulation test, CBC, tick panel. • If those are normal, then check bone marrow

19. Immune Mediated Thrombocytocenia • Most common in middle-aged female dogs, less common in cats. • May be primary cause similar to AIHA. • Secondary causes are drugs, viruses, immune complexed, infectious disease, etc.

20. Coagulopathy • Test platelets • Platelet count • Bleeding time • Test Coagulation Factors • Activated Clotting Time (ACT) • Activated Partial Thromboplastin Time (PTT) • Prothrombin Time (PT)

21. Disorders of Blood Coagulation Factors • Von Willebrand disease (vWD): factor VIII decreased. • An additional portion of the molecule which is important in platelet function is decreased or absent. • Abnormal platelet function. • Increased mucosal surface bleeding time. • Excessive surgical bleeding. • Chronic, low grade bleeding possible. • PTT may be mildly prolonged • Antigen test

22. Buccal Mucosal Bleeding Time • Normal clotting time 2-4 minutes • Platelet dysfunction at 10-12 minutes • Begin timing immediately after making cut. Wound should not be wiped or disturbed until it has clotted.

23. Cuticle Bleeding Time • Normal time is 2-8 minutes • Begin timing at the time the nail is cut. Discrete drops of blood should fall from wound. A steady stream indicates that the wound is too far in the cuticle.

24. Equine Infectious Anemia (EIA) • Contagious and potentially fatal viral disease in horses. • No vaccine or treatment exists. • Transmitted by biting insects such as horseflies and deerflies. • Can also be transmitted by dirty needles. • Also called Swamp Fever • Two stages: • Acute • Develops severe, acute signs within 2-3 weeks. Signs occur rapidly and cause only a slight increase in temperature, 30% of horses die at this stage • Chronic • Temperature > 105˚ F

25. Clinical Signs of EIA • Petechial hemorrhage • Depression • Weight loss • Edema in legs and abdomen • Anemia

26. Coggins Test • Checks for antibodies to the virus • Positive Test Options • 1. Retest • 2. Euthanize • 3. Sale for immediate slaughter • 4. Lifetime Quarantine

27. Texas Law and Reactors • Retest in 30 days at TVMDL • Official reactors are permanently marked by using a National Uniforms Code branded on the left shoulder or neck. • Quarantine should be at least 200 years from other equine • All exposed equines must be tested

28. Common Blood Parasites you should know • Ehrlichia platys • Brown dog tick transmits • Erhlichia canis • Common in TX • Transmitted by Brown dog tick • 3 stages of disease • (acute, subclinical, and chronic) • Hemobartonella felis • FIA (feline infectious anemia) • Rickettsial organism • Transmitted by fleas, ticks, blood transfusions, queen to kitten. • Hemobartonella canis • Rarely seen in dogs • Cytauxzoon felis • Fatal disease characterized by anemia • Thought to be transmitted by ticks • Anaplasma marginale • Rickettsial organism • Transmitted mechanically through equipment • Babesia bigemina • Reportable in cattle • Texas fever, Redwater fever, Cattle tick fever • Babesia canis • Babesia Gibsoni