Hematology of Lizards, Crocodilians, and Tuatara

A mystery revealed: an update on eosinophil and other blood cell morphology of the Argentine black and white tegu (Salvator merianae)

“…Hematological evaluation of reptiles can be challenging due to species differences in white blood cell (WBC) morphology, proportions, and cytochemical staining patterns (1)(2)(3). Accurate light microscopic differentiation of a given species in health is important for obtaining reference intervals and interpreting leukogram changes, both of which can be affected by various pre-analytical intrinsic and extrinsic factors (e.g., environment, sex, diet, and methodology) (1,3). Argentine black and white tegus (Salvator merianae) are large, omnivorous South American lizards (order Squamata, family Teiidae) closely related to whiptail lizards (genus Aspidoscelis and Cnemidophorus) (4,5).…”

“…Hematological evaluation of reptiles can be challenging due to species differences in white blood cell (WBC) morphology, proportions, and cytochemical staining patterns ( 1–3 ). Accurate light microscopic differentiation of a given species in health is important for obtaining reference intervals and interpreting leukogram changes, both of which can be affected by various pre-analytical intrinsic and extrinsic factors (e.g., environment, sex, diet, and methodology) ( 1 , 3 ). Argentine black and white tegus ( Salvator merianae ) are large, omnivorous South American lizards (order Squamata, family Teiidae) closely related to whiptail lizards (genus Aspidoscelis and Cnemidophorus ) ( 4 , 5 ).…”

Data_Sheet_1.pdf

“…The nature and clinical relevance of the inclusions are unknown. The inclusions do not have a crystalloid appearance, and no correlation can be made between the presence of these inclusions and inflammation as similar cells, with the inclusions, have been observed in closely related species, such as healthy red tegu and Savannah monitor lizards (3). The lack of reactivity with PAS and SBB suggests they are not composed of glycogen, glycogen-containing substances, or lipids.…”

“…Previous publications have reported that eosinophils in the Argentine black and white tegu are indistinguishable from heterophils with the May-Grűnwald-Giemsa stain (6)(7)(8). Monocytes in this species are described as containing an electron-lucent variably shaped inclusion (6), while another report describes WBCs containing oval to linear cytoplasmic clearings of unknown origin in an apparently healthy red tegu (Salvator rufescens) and a Savannah monitor (Varanus exanthematicus) (3), which is from a different taxonomic family (Varanidae). The objective of this study was to perform a suite of cytochemical staining and transmission electron microscopy (TEM) on blood submitted for a complete blood count (CBC) from one Argentine black and white tegu to identify the cellular origin of the WBC with the previously described inclusion/cytoplasmic clearing that has been a mystery to date.…”

“…Hematological evaluation of reptiles can be challenging due to species differences in white blood cell (WBC) morphology, proportions, and cytochemical staining patterns (1)(2)(3). Accurate light microscopic differentiation of a given species in health is important for obtaining reference intervals and interpreting leukogram changes, both of which can be affected by various pre-analytical intrinsic and extrinsic factors (e.g., environment, sex, diet, and methodology) (1,3). Argentine black and white tegus (Salvator merianae) are large, omnivorous South American lizards (order Squamata, family Teiidae) closely related to whiptail lizards (genus Aspidoscelis and Cnemidophorus) (4,5).…”