WCH Clinical Toxinology Resources

Haematologic_toxins_overview

Toxins affecting blood coagulation

The human haemostatic system seems a favourite target of snake venoms. There are toxins targeting almost all parts of the system, represented in three of the four snake families (Colubridae, Elapidae, Viperidae). The major toxin groups include procoagulants, anticoagulants, platelet aggregation inhibitors and promoters. The net effect of most of these toxins is to increase bleeding, particularly when combined with haemorrhagins, but a few venoms cause clinical thrombosis, with potential for embolic problems. The mechanisms of increased bleeding vary, but most components acting as procoagulants exert their effect by consumption of fibrinogen, resulting in defibrination rather than classic DIC, thus the thrombocytopenia associated with DIC is often absent. However, some venoms do cause thrombocytopenia through other mechanisms. Yet other venoms cause defibrination by direct action on fibrinogen, splitting fibrinopeptides inappropriately. The biochemical nature and structure of these diverse toxins varies from comparatively small molecules to large, complex multi-component toxins that mimic normal clotting complexes such as the prothrombinase complex. The majority of viper species have toxins affecting coagulation, but only a few Elapid species, notably those from Australia and New Guinea, cause similar effects.

Principal types of toxin effects on the haemostatic system.

Toxin type	Effect
Procoagulants	Factor V activating Factor X activating Factor IX activating Prothrombin activating Fibrinogen clotting
Anticoagulant	Protein C activating Factor IX/X activating protein Thrombin inhibitor PLA2
Fibrinolytic	Fibrin(ogen) degradation Plasminogen activation
Vessel wall interactive	Haemorrhagin
Platelet activity	Platelet aggregation inducers Platelet aggregation inhibitor
Plasma protein activators	SERPIN inhibitor

Snakes considered to cause medically significant effects on the haemostatic system.

Scientific name	Common name	Effect
COLUBRIDAE
Dyspholidus typus	Boomslang	Coagulopathy & haemorrhage
Thelotornis spp.	Vine snakes	Coagulopathy & haemorrhage
Rhabdophis spp.	Yamakagashi, red necked keelback	Coagulopathy & haemorrhage
ELAPIDAE
Hoplocephalus spp.	Australian broad headed snakes	Coagulopathy & haemorrhage
Micropechis ikaheka	New Guinea small eyed snake	Anticoagulant & haemorrhage
Notechis spp.	Australian tiger snakes	Coagulopathy & haemorrhage
Oxyuranus spp.	Australian taipans	Coagulopathy & haemorrhage
Pseudechis spp.	Australian mulga snakes	Anticoagulant & haemorrhage
Pseudonaja spp.	Australian brown snakes	Coagulopathy & haemorrhage
Tropidechis carinatus	Rough scaled snake	Coagulopathy & haemorrhage
VIPERIDAE
Agkistrodon spp.	American copperheads	Coagulopathy & haemorrhage
Bitis spp.	African puff adders, Gaboon vipers etc	Coagulopathy & haemorrhage
Bothrops spp. Includes Bothriechis, Cerriphidion, Ophryacus, Porthidium spp.	Central & South American pit vipers	Coagulopathy & haemorrhage
Bothrops lanceolatus	Martinique viper	Coagulopathy; thrombosis with DVT and pulmonary embolus
Calloselasma rhodostoma	Malayan pit viper	Coagulopathy & haemorrhage
Cerastes spp.	North African horned vipers	Coagulopathy & haemorrhage
Crotalus spp. (selected)	North American rattlesnakes	Coagulopathy & haemorrhage
Daboia russelii	Russell’s viper	Coagulopathy & haemorrhage
Echis spp.	Saw scaled vipers	Coagulopathy & haemorrhage
Lachesis spp.	Bushmasters	Coagulopathy & haemorrhage
Trimeresurus spp.	Green pit vipers	Coagulopathy & haemorrhage
Vipera spp. (selected) Includes Macrovipera spp.	Selected European vipers	Coagulopathy & haemorrhage

Return To Snake Venoms Overview Page

Return to Snakes Home Page

IMPORTANT INFORMATION FOR ALL SITE USERS : The principle aim of this site is to provide information useful to improving outcomes for humans suffering from envenoming or poisoning by animals, plants or mushrooms. We make a reasonable attempt to verify accuracy of information listed on this site. However, we cannot access every published paper of potential relevance, either because they are not available to us or are in a language we cannot translate internally. Equally, we cannot list knowledge which is not yet reported or known. It should not be assumed that humankind currently knows all there is to know about any species, even for common species. Further, we cannot control how users will interpret the information provided on this site. We therefore do not accept legal responsibility for use of the information provided and we require that all users use information from this site at their own risk.
The following should also be noted when reading information contained within the databases on this website: italics for scientific nomenclature cannot be displayed, and superscripting and subscripting is absent in some instances.
Photos downloaded from Wikimedia Commons or other website are licensed for use under the Creative Commons Attribution-Share Alike 2.0 Generic license (CC BY-SA 2.0), 2.5 Generic license (CC BY-SA 2.5) or 3.0 Unported license (CC BY-SA 3.0), or the Attribution-NonCommerical-ShareAlike 3.0 Unported license (CC BY-NC-SA 3.0), or the Attribution-Share Alike 4.0 International license (CC BY-SA 4.0), or the GNU General Public License (GPL3.0), or in the Public Domain (PD), as shown in the caption to the image displayed on www.toxinology.com.