Anemia, Thrombocytes, and Blood Parasites

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Anemia, Thrombocytes, and Blood Parasites

• Clinical Pathology

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Autoimmune Hemolytic Anemia (AIHA)

• Antibodies directed against RBC membrane antigens
  and Ab- coated RBCs 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.

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AIHA continued

• The spleen is the primary site for removal of
  RBCs coated with IgG while the liver removes
  RBCs coated with IgM.
• Onset of anemia may be acute or gradual.
• Complications
• DIC
• Pulmonary Thromboembolism

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Causes of AIHA

• Primary AIHA autoantibodies directed against
  RBCs 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.

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Diagnosis

• History and Physical Exam
• CBC
• Regeneration
• Spherocytes
• Autoagglutination
• Anemia (PCVlt20)
• Coombs Test
• Splenomegaly and Hepatomegaly seen on radiographs.

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Therapy for AIHA

• Corticosteriods
• Reduces clearance of Ab coated RBCs 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.

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Classification of Nonregenerative Anemia

• Primary failure of erythropoiesis
• Secondary failure of erythropoiesis
• Nuclear maturation defects
• Hemoglobin synthesis defects
• Aplastic anemia
• Marrow infiltration

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Primary Failure of Erythropoiesis

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

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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.

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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.

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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.

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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

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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.

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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

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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

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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.

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Coagulopathy

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

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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

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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.

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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.

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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 gt 105 F

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Clinical Signs of EIA

• Petechial hemorrhage
• Depression
• Weight loss
• Edema in legs and abdomen
• Anemia

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Coggins Test

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

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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

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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