Snake Toxins and Endothelium

HISTORY OF SNAKE TOXINS AND THEIR EFFECTS ON ENDOTHELIUM Venomous snakes are by far the most feared of venomous animals. Four families of venomous snakes exist: the Viperidae (which includes vipers, adders, and pit vipers), the Elapidae (which includes the cobras, mambas, kraits, coral snakes, and sea snakes), the Colubridae (which includes the venomous rear-fanged snakes such as the boomslang and the twig snake), and the Atractaspididae – the family termed the burrowing snakes . In most developed countries, fatalities associated with snake envenoming are rare; however, in many tropical regions in places such as Africa, South America, and Southeast Asia, snake envenomation often is associated with a relatively high mortality rate. By definition, venomous snakes are snakes that produce venom. Approximately 2,700 different snake species exist, of which nearly one-fifth are venomous (1). Interestingly, many of the venomous snakes rarely, if ever, envenomate humans and hence are falsely considered nonvenomous. From the earliest observations of viperid snake envenomations, it was obvious that severe coagulopathic consequences occurred at both the local and systemic level. These coagulopathies, although not necessarily absent in envenomations by other snakes from other venomous families, were certainly more pronounced with snakes from Viperidae. In 1664, Francisco Redi (1626–1697) discovered that it was the venom from the snake that caused the “direful effects” associated with the bite of a snake (2). The Italian scientist Felice Fontana (1720–1805) was the first to study the effect of snake venom on blood and recognized that the effect of venom on blood coagulation properties was directly related to the toxicity of the venom (3).