engleski

Blood cell morphology in animal species

Despite considerable progress, a routine clinical hematology is still based on identification of morphological quantitative and qualitative changes of peripheral blood cells and hematopoietic organs. A basic instrument is the stained blood smear and the accuracy of obtaining information requires the correct technique of making smears in order to avoid possible confusing artifacts and disarranged distribution of cells which leads to serious mistakes of differential counting and interpretation of findings. However, in veterinary medicine, the possibility of a mistake begins already during blood sampling. Animals not used to handling should be immobilized, by physical restraint or by using tranquillizers and anesthetics, which can cause changes in the number and appearance of red blood cells and platelets. Furthermore, although EDTA is the preferred anticoagulant for blood morphology studies for most animal species, EDTA causes hemolysis in blood samples obtained from some groups of birds and reptiles. In these animal species heparin is the most commonly used anticoagulant that interferes with proper staining of the blood cells. Evaluation of blood cell morphology in veterinary medicine requires a very long training and experience of veterinary practicians, since today not only domestic but also wild and exotic animals appear as patients. A wide range of specific morphologic characteristics of blood cells in different animal species are expressed. Starting with the red blood cells that are in most mammalian species in a shape of biconcave disc, but in camelids they are elliptic. Goats often have a spindle and fusiform erythrocytes, and in cervids a high percentage of erythrocytes are found in a shape of drepanocytes. Furthermore, erythrocytes of birds, fish and reptiles contain a nucleus. The dynamics of erythrocytes maturation also differ, as well as their release in the peripheral blood, so consequently, depending on animal species, different characteristics of regenerative blood film in a response to anemia are recognized. Regarding the leukocytes, the greatest morphologic diversity due to animal species and breeds we find in the eosinophils. By the number, appearance and intensity of staining eosinophilic granules, we can with great certainty know from which animal does the blood smear originate. A great challenge is to distinguish eosinophils from heterophils in small rodents, birds and reptiles. Heterophils in their role of defending the organism respond to neutrophils, but their granules are stained red. Basophils in birds and reptiles have a round nucleus, unlike the typical segmented nucleus in the mammalian. Morphologic characteristics of lymphocytes are very similar in all animals, while some shapes of monocytes nuclei are more common in particular animal species. Platelets in birds and reptiles have a nucleus and can be easily mistaken for lymphocytes by insufficiently experienced hematologists. In reptiles, another cell type is distinguished, the azurophiles, whose role and origin has not yet been fully understood. Therefore, due to the number and variety of animal species, in veterinary hematologic cytology, an extensive knowledge and experience is needed in identifying physiological blood cell morphology and it is a prerequisite for proper evaluation of morphological changes in various pathological conditions.

cell morphology; different animal species

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