E

E



Eccentrocyte



DEFINITION


Erythrocyte damaged by oxidants. Characterized by focal area of fused membranes with eccentric displacement of hemoglobinized cytosol and loss of any central pallor. The collapsed area with fused membranes appears as a clear area at periphery of erythrocyte which is outlined by a barely visible cell membrane.



SYNONYMS


Bite cell, hemighost



TYPICAL NORMAL RANGE


Absent in health



PHYSIOLOGY


During oxidative damage, hemichromes (oxidized forms of hemoglobin) bind to the band 3 protein of the membrane cytoskeleton. This creates cross-linking and fusion of the erythrocyte cytoskeleton and alters the membrane, with externalizing of antigenic proteins and attachment of autoantibodies. Hemichromes can also precipitate to form Heinz bodies.



CLINICAL APPLICATION



CAUSES OF ABNORMALLY HIGH LEVELS



• Oxidative damage to erythrocyte from toxins such as acetaminophen, onions, and benzocaine in dogs and cats, zinc and garlic in dogs. Heinz bodies may also be seen in conjunction with eccentrocytes.

• Also reported in dogs with vitamin K antagonist intoxication, T-cell lymphoma, and diabetic ketoacidosis

• Decreased antioxidant activity of erythrocytes (rare): congenital deficiency of glucose-6-phosphate dehydrogenase, with decreased production of reduced nicotinamide adenine dinucleotide phosphate (NADPH) in erythrocytes NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Evaluate history for source of oxidative damage to erythrocytes.


SPECIMEN AND PROCESSING CONSIDERATIONS


DRUG EFFECTS: Associated with propofol anesthesia in dogs


SPECIMEN: EDTA whole blood and freshly prepared blood smear for lab to stain


RELATIVE COST: $$ (reported as part of


CBC)


AUTHOR: STEPHEN D. GAUNT



Ehrlichia Serology



DEFINITION


Detection of serum antibodies directed against Ehrlichia spp. (most commonly E. canis)



TYPICAL NORMAL RANGE


Reporting differs among reference laboratories. Consult with laboratories for proper interpretation of values.



PHYSIOLOGY


Ehrlichia spp. are rickettsial agents that infect a wide range of host species. Numerous species of Ehrlichia have been shown to infect dogs. E. canis produces an acute disease (canine monocytic ehrlichiosis) from which animals recover, but which typically remains subclinical and may later produce more severe disease. Early (7 days post infection) titers are due to immunoglobulin (Ig)A and IgM; 3 weeks postinfection titers are mostly due to IgG. Most laboratories measure IgG.



CLINICAL APPLICATIONS



CAUSES OF ABNORMALLY HIGH LEVELS



• The presence of antibodies directed against E. canis indicates exposure to E. canis or related organisms. Some antigens of E. canis, E. ewingii, and E. chaffeensis are cross-reactive, whereas others are not.

• A positive titer indicates only exposure and does not prove that current clinical signs are due to active infection.

• E. canis can cause a persistent subclinical infection, so a dog with a positive titer is likely to still be infected unless treated with appropriate antimicrobial therapy.

NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS HIGH: Evaluate whether the patient’s current signs are consistent with ehrlichiosis, and consider treatment with appropriate antimicrobial therapy. A positive test for ehrlichial DNA via PCR supports active infection and can determine the specific species of Ehrlichia involved.


CAUSES OF ABNORMALLY LOW LEVELS: Infection with different Ehrlichia spp.


NEXT DIAGNOSTIC STEP TO CONSIDER IF LEVELS LOW: If a clinical suspicion for ehrlichiosis persists despite a negative titer to E. canis, titers to other ehrlichial species (e.g., Anaplasma phagocytophilum, formerly E. equi) should be performed, because cross-reactivity does not occur reliably.



SPECIMEN AND PROCESSING CONSIDERATIONS


IMPORTANT INTERSPECIES DIFFERENCES: Serologic tests often use species-specific reagents, and Ehrlichia serologic testing is most often performed on dogs. Check with lab as to appropriateness if testing cats.


SPECIMEN: Serum (red-top)


RELATIVE COST: $$



PEARLS



• Some dogs maintain persistent titers for years despite appropriate therapy and apparent resolution of disease.

• An in-clinic, ELISA-based serology test (SNAP4Dx, IDEXX Labs) for detecting E. canis antibody appears to have high specificity when compared with immunofluorescent assay, but it may not detect low titers.

• Dogs may have negative titers if early in infection or if infected with other ehrlichial species other than those being evaluated.

• Ehrlichia serologic testing is much more sensitive (i.e., better screening test) than evaluating a blood smear for the presence of ehrlichial inclusions in leukocytes.

AUTHOR: LOIS ROTH-JOHNSON


1ST EDITION AUTHOR: JAMES H. MEINKOTH



Eosinophils



DEFINITION


Granulocytic leukocyte with eosinophilic granules in cytoplasm and a segmented nucleus

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on E

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