Exotic Animal Hematology and Cytology

Left shift and toxic change in heterophils and neutrophils of non‐mammalian vertebrates: A comparative review, image atlas, and practical considerations

“…Many species of bony fish (eg, koi, catfish) have neutrophils, with some bony fish species (eg, South American trout, Oncorhynchus mykiss ) having heterophils and neutrophils, concurrently 7,9,10 . Amphibians have neutrophils, while birds and reptiles have heterophils 1,2 . The size of these cells also varies substantially across taxa (Figure 3).…”

“…The nuclei of mature neutrophils or heterophils of some bony fish species are small and round, while others are segmented. Heterophil nuclei in most reptile species are also small and round, with the exception of lobulated/segmented nuclei in some lizards and tuatara 1,12 . A blue‐staining region at the rim of one side of the nucleus is fairly common in reptilian heterophils, especially in chelonians (Figure 1AF‐AG), and can assist with differentiation from eosinophils.…”

“…A blue‐staining region at the rim of one side of the nucleus is fairly common in reptilian heterophils, especially in chelonians (Figure 1AF‐AG), and can assist with differentiation from eosinophils. Nuclei in heterophils of birds are consistently segmented 1,2 …”

“…Instead, the overall morphologic diversity across NMV favors simplified classification schemes. Current methods of reporting left shifts in NMV include a subjective description of mild, moderate, or marked left shifts or the presence/absence thereof 1,40 . A classification system characterizing granulocytes as mature or immature has been used in elasmobranchs and selectively in birds and reptiles 6,41,42 .…”

“…Despite the universally central role of heterophils and neutrophils in routine inflammatory responses of vertebrates, literature on left shifts and toxic change in non‐mammalian vertebrates (NMV) is scarce and often focused on one taxon or species 1,2 . The objectives of this report are to (a) review heterophil and neutrophil function and structure across the vertebrate animal kingdom, (b) compare morphologic features of left shift and toxic change in heterophils and neutrophils of NMV to mammals, (c) provide an image guide demonstrating the breadth of morphologic diversity of heterophil and neutrophil lineages in health and disease across taxa, and (d) discuss practical considerations for clinical pathologists and other professionals involved in recognition and interpretation of observations in the inflammatory leukogram of NMV.…”