Medically Important Snakes

          Medically important snakes in Malaysia largely originate from the Elapidae family and the Crotalinae subfamily. Venoms of many elapid snakes (cobra, krait and sea snakes) generally produce flaccid paralysis and respiratory difficulty leading to asphyxia. Elapid venoms mainly contain proteins/peptides of low to moderate molecular mass (<15 kDa), with one key group called the three-finger toxins (6-8 kDa), which include various neurotoxins and cytotoxins (or cardiotoxins). On the other hand, crotalid venoms constitute moderate to high molecular mass proteins (>15 kDa), many of which are enzymes, e.g., thrombin-like serine proteases, metalloproteinases, L-amino acid oxidases, etc. However, phospholipases A2 present usually in substantial amount in both the elapid and crotalid venoms. The envenoming effect of elapid bites usually develops rapidly, and death can ensue within hours. In contrast to rapid neuromuscular paralysis by the elapids, pit viper bites tend to develop more insidious and manifest more often as hemorrhage and coagulopathy. With the advancement in molecular phylogenetics in the last two decades, the taxonomy of many medically important snakes including those in Malaysia has been extensively revised, making interpretation of findings from earlier works difficult. The importance of development in snake systematics, however, cannot be overlooked in the field of medical toxinology, as venom compositions often vary extensively even between very closely related species or subspecies, resulting in a diverse presentation of envenoming effects and inconsistent therapeutic response to antivenom therapy.