Hematological and coagulation alterations and splenic response following Macrovipera lebetina obtusa envenomation: Evaluation of ovine-derived experimental antivenom.

Macrovipera lebetina obtusa (M. l. obtusa) is the most medically significant viper species in Armenia and the region, responsible for the majority of snakebite cases. This study investigated the hematological, coagulation, and histopathological effects of M. l. obtusa envenomation in rats and mice, and evaluated the therapeutic efficacy of an ovine-derived experimental antivenom. Hematological analysis revealed significant increases in red blood cell (RBC) count and hemoglobin (HGB) concentration following envenomation, suggestive of hemoconcentration likely due to vascular leakage. Coagulation studies demonstrated marked prolongation of prothrombin time (PT) and activated partial thromboplastin time (APTT), indicating venom-induced coagulopathy. Notably, PT was more severely affected, and its elevation persisted even after antivenom administration, suggesting incomplete neutralization of venom activity. Histopathological examination of spleen and skin tissues showed progressive structural disruption, including hemorrhage, edema, and lymphoid follicle hyperplasia, which remained evident up to seven days post-envenomation. While the experimental antivenom provided partial systemic protection and improved some hematological parameters, it was unable to reverse the venom-induced tissue and coagulation abnormalities fully. These findings highlight the complex pathophysiology of M. l. obtusa venom and underscore the need for adjunctive therapies targeting vascular integrity and immune regulation in the management of viper envenomation.