Haemostasis disorders caused by envenomation by Cerastes cerastes and Macrovipera mauritanica vipers

Novel Toxicodynamic Model of Subcutaneous Envenomation to Characterize Snake Venom Coagulopathies and Assess the Efficacy of Site-Directed Inorganic Antivenoms

Venomous snake bite adversely affects millions of people yearly, but few animal models allow for the determination of toxicodynamic timelines with hemotoxic venoms to characterize the onset and severity of coagulopathy or assess novel, site-directed antivenom strategies. Thus, the goals of this investigation were to create a rabbit model of subcutaneous envenomation to assess venom toxicodynamics and efficacy of ruthenium-based antivenom administration. New Zealand White rabbits were sedated with midazolam via the ear vein and had viscoelastic measurements of whole blood and/or plasmatic coagulation kinetics obtained from ear artery samples. Venoms derived from Crotalus scutulatus scutulatus, Bothrops moojeni, or Calloselasma rhodostoma were injected subcutaneously, and changes in coagulation were determined over three hours and compared to samples obtained prior to envenomation. Other rabbits had ruthenium-based antivenoms injected five minutes after venom injection. Viscoelastic analyses demonstrated diverse toxicodynamic patterns of coagulopathy consistent with the molecular composition of the proteomes of the venoms tested. The antivenoms tested attenuated venom-mediated coagulopathy. A novel rabbit model can be used to characterize the onset and severity of envenomation by diverse proteomes and to assess site-directed antivenoms. Future investigation is planned involving other medically important venoms and antivenom development.

A Genus-Wide Bioactivity Analysis of Daboia (Viperinae: Viperidae) Viper Venoms Reveals Widespread Variation in Haemotoxic Properties

The snake genus Daboia (Viperidae: Viperinae; Oppel, 1811) contains five species: D. deserti, D. mauritanica, and D. palaestinae, found in Afro-Arabia, and the Russell's vipers D. russelii and D. siamensis, found in Asia. Russell's vipers are responsible for a major proportion of the medically important snakebites that occur in the regions they inhabit, and their venoms are notorious for their coagulopathic effects. While widely documented, the extent of venom variation within the Russell's vipers is poorly characterised, as is the venom activity of other species within the genus. In this study we investigated variation in the haemotoxic activity of Daboia using twelve venoms from all five species, including multiple variants of D. russelii, D. siamensis, and D. palaestinae. We tested the venoms on human plasma using thromboelastography, dose-response coagulometry analyses, and calibrated automated thrombography, and on human fibrinogen by thromboelastography and fibrinogen gels. We assessed activation of blood factors X and prothrombin by the venoms using fluorometry. Variation in venom activity was evident in all experiments. The Asian species D. russelii and D. siamensis and the African species D. mauritanica possessed procoagulant venom, while D. deserti and D. palaestinae were net-anticoagulant. Of the Russell's vipers, the venom of D. siamensis from Myanmar was most toxic and D. russelli of Sri Lanka the least. Activation of both factor X and prothrombin was evident by all venoms, though at differential levels. Fibrinogenolytic activity varied extensively throughout the genus and followed no phylogenetic trends. This venom variability underpins one of the many challenges facing treatment of Daboia snakebite envenoming. Comprehensive analyses of available antivenoms in neutralising these variable venom activities are therefore of utmost importance.

Rosemary leaves extract: Anti-snake action against Egyptian Cerastes cerastes venom

The morbidity caused by viper bites is very dangerous and the anti-venom therapy couldn't treat the local injures such as hemorrhage, edema, necrosis and inflammation of bitten tissues. Searching for safe and effective anti-venom compounds from natural sources is very important. This study was designed to explore the neutralizing ability of Rosmarinus officinalis L. leaves aqueous extract (RMAE) against Egyptian Cerastes cerastes (Cc) viper venom toxicity. The RMAE contained a considerable amount of phenolic and flavonoid contents with 3,300 and 800 mg/100 g dry weight, respectively. The RMAE showed a considerable variation of phenolic acids by using HPLC technique. Rosmarinic acid is the major component of the RMAE which recorded 400 mg/100 g dry weight and 64% of all the identified compounds. In vitro, the RMAE neutralized the enzymatic activities of proteases, l-amino acid oxidases, and phospholipases A2 of the Cc venom dose-dependently. In addition, the RMAE effectively neutralized the gelatinolytic, fibrinogenolytic, hemolytic and procoagulant activities of Cc venom. In vivo, the RMAE markedly reduced lethality, hemorrhage, edema, muscle and liver toxicities induced by Cc venom. In conclusion, the venom neutralizing property of the RMAE gives a new prospect for efficient treatment of the lethal viper bites.