Investigations on Blood Coagulation in the Green Iguana (Iguana iguana)

Abstract

The prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time, kaolin clotting time (KCT), dilute Russell's viper venom time (DRVVT) and reptilase time, as well as five different plasma fibrinogen assays [gravimetry, Jacobsson method (extinction at 280 nm), Millar method (heat precipitation), kinetic turbidometry, Clauss method] and resonance thrombography were performed in 26 clinically healthy green iguanas. All assays were carried out in comparison with pooled normal canine plasma. In iguana plasma, the PT [median (x0.50) = 453-831 s, dependent on the reagent], APTT (x0.50 = 170-242 s, dependent on the reagent), thrombin time (x0.50 = 118 - > 1000 s, dependent on thrombin activity), KCT (x0.50 = 274 s), DRVVT (x0.50 = 349 s) and reptilase time (all samples > 1000 s) were widely scattered at the limit of measurability. Only fibrinogen concentrations measured using the Jacobsson method (x0.50 = 4.40 g/l) correlated well (r = 0.91) with gravimetry (x0.50 = 4.22 g/l). The results of this study indicate a limited suitability and a confined diagnostic significance of the selected methods in the green iguana. This may be caused by the species specificity of certain components of the reagents used, as well as a less optimal test system, i.e. relationship of test reagent to clotting factor concentrations in iguana plasma.

Coagulation testing in green iguanas (Iguana iguana) with development of prothrombin time assays using reptile and avian thromboplastin

“…The median PT using reptile thromboplastin was 34.8 seconds and using avian thromboplastin was 78.5 seconds, as compared to times ranging from several hundred to more than a thousand seconds when mammalian-based thromboplastin was used. 8 The ability to measure PTs in this species using avian thromboplastin derived from chicken brains suggests the possibility of creating a commercially available PT test for birds and reptiles by using a more readily available source of thromboplastin. Although results were obtained with both reptile-derived and avian-derived brain thromboplastin, there may be some benefit of using a conspecific thromboplastin, if available, and may account for the faster time from the reptile-derived product.…”

“…7 In green iguanas (Iguana iguana), PTs were markedly prolonged and variable using 5 different reagents, thrombin times, and dilute Russell's viper venom times (RVVT), or no clot formation occurred, which limited the clinical usefulness of the tests in this species. 8 The objective of this study was to evaluate the extrinsic and common coagulation pathways in green iguanas, using avian/reptile extrinsic pathway activators and commercially available coagulation screening test reagents, respectively. Specifically, PT assays were configured with avian/reptile brain thromboplastins.…”

Effects of brodifacoum and diphacinone exposure on four species of reptiles: tissue residue levels and survivorship

“…Reptiles, and other poikilotherms, have noteworthy differences in physiology and specifically blood chemistry compared to their mammalian counterparts. There are numerous reports stating that clotting time in reptiles is greatly increased when compared to mammals . Although reptiles have the extrinsic clotting pathway, differences in many of the other factors have been reported .…”

“…There are numerous reports stating that clotting time in reptiles is greatly increased when compared to mammals. [25][26][27][28][29][30][31] Although reptiles have the extrinsic clotting pathway, differences in many of the other factors have been reported. 32 Spectacled caimans are missing factors V, VII, IX, and XI of the intrinsic (vitamin K dependent) pathway.…”

Fibrinolysis and Thrombolysis

“…There is no evidence of a fibrinolytic system in reptiles, lizards (Trachydosaurus rugosus rugosus, Tiliqua scincoides, Amphibolorus barbatus, Varanus acanthrus, Iguana iguana), turtles (Chelodina longicollis), crocodiles (Crocodylus porosus) or pitons (Liasis spp, Morelia spp) (Tables 1 and 10). A strong circulating antithrombin protects these vertebrates from intravascular thrombosis (Hackett and Hann 1964;Kubalek et al 2002), however low concentrations of α2PI were detected in the circulation of the snake Bitis arietans using a chromogenic method (Table 10).…”