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XI
AVIAN AND REPTILIAN CLINICAL PATHOLOGY
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Introduction to Avian and Reptilian Clinical Pathology
Armando R. Irizarry-Rovira
The chapters in this section are not intended as a definitive or extensive discourse on normal avian hematology and diagnosis of avian hematologic disorders (Chapter 49), avian biochemical analysis (Chapter 50), normal reptilian hematology and diagnosis of reptilian hematologic disorders (Chapter 51), reptilian biochemical analysis (Chapter 52), or avian and reptilian cytology (Chapter 53). These chapters are solely intended as quick reference guides to these fascinating areas of avian and reptilian medicine. The discussions focus on the use of hematologic and biochemical principles to help diagnose diseases in pet birds (Chapters 49 and 50) and pet reptiles (Chapters 51 and 52) and the use of cytologic principles to diagnose diseases in live and dead birds and reptiles (Chapter 53). Diseases of wild birds and poultry are mentioned where appropriate to complement the discussion in Chapters 49 and 50.
For detailed discussions on the subjects addressed in these chapters, refer to the Bibliography following Chapter 53.
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49 AVIAN HEMATOLOGY
1 How are avian blood cells different from the blood cells of mammals?
Avian blood cells are similar to mammalian blood cells in some aspects but differ significantly in others, particularly morphology. As in mammals, avian blood cells include erythrocytes, leukocytes, and thrombocytes (platelets), all of which are easily evaluated by examination of air-dried, Romanowsky-stained blood smears.
2 What are some important principles to understand about the identification of avian leukocytes by blood smear evaluation?
a. Proper identification of leukocytes depends on familiarity with the morphology of leukocytes and the species of bird, prompt processing of the blood sample, quality of the blood smear, and staining techniques used to visualize the leukocytes.
b. Fresh blood (no anticoagulant) and ethylenediaminetetraacetic acid (EDTA) or heparin anticoagulated blood samples are both satisfactory for use in the identification of leukocytes, but fresh blood smears are preferred. When cell enumeration is required, it is best to keep samples at a cool temperature when shipping. Long transit times may result in inaccurate leukocyte counts, abnormal morphology, or hemolysis (e.g., ostrich erythrocytes in EDTA).
c. Gaining familiarity with leukocyte morphology requires frequent examination of blood samples from normal and sick patients of various species. Staining affinity of cytoplasmic granules may vary between species of birds.
d. Use of consistent staining techniques and methods is important to avoid excessive variation in cell staining and to ensure consistent and accurate leukocyte identification.
e. Formalin fumes, even if the source is a few feet away, will alter cellular proteins in such a way that the staining intensity and affinity of leukocytes will be altered. Therefore, blood smears should be kept away from formalin sources and stained promptly.
f. If a blood smear must be stored for longer periods, either for later examination or for archiving, immersion oil should be removed with appropriate solvents and the slide permanently coverslipped.
3 Describe the various avian leukocytes.
Avian leukocytes include the heterophil, basophil, monocyte, lymphocyte, and eosinophil. Descriptions are based on Romanowsky-stained (e.g., Wright-Giemsa, Diff-Quik) blood smears.
a. The heterophil is the predominant leukocyte in health in many avian species and predominates in many disease conditions (Figure 49-1). It has a lobulated, condensed nucleus, although the degree of lobulation is less than that of mammals. The heterophil of most bird species has a cytoplasm that is filled with elongate, rod- to spindle-shaped, orange to brick-red granules.
b. The eosinophil has prominent small, round cytoplasmic granules that vary in color from bright red to pink depending on the species (Figure 49-2). In a few species the granules may appear lavender blue using Romanowsky-type stains. The eosinophil is not seen as frequently as the heterophil, and the granules of the eosinophil will stain differently than those of the heterophil within the same blood smear. Compared with other bird species, raptors tend to have slightl...
