Snake venoms consist mainly of proteins and peptides (>90%) that exhibit diverse biochemical and pharmacological activities. Venom represents a trophic adaptive trait, and is unique among species. The complexity of venom develops through a series of evolutionary events that include repeated gene duplication and molecular adaptation, leading to protein neofunctionalization to suit the toxin roles in predation, digestion and defence. The major contents and biochemical activities of venoms from phylogenetically closely related species generally share a similar pattern; for example the predominance of muscle-paralysing neurotoxins (alpha-, beta- and kappa-neurotoxin) in the venoms of most elapid snakes. Nevertheless, venom composition (toxin subtypes and relative abundances) can vary remarkably between congeneric or even intraspecific species as a result of differences in their ecological niche and the consequent genetic adaptation. The implication of this phenomenon is medically relevant, as diverse toxin composition can lead to varied envenoming effects and treatment outcome, where antivenom’s action is usually species-specific.
It is known that in Southeast Asia, many countries depend on antivenom supply from non-domestic manufacturers that use immunogens from species non-native to the importing countries. This poses a question of how appropriate or effective the antivenoms are for heterologous or non-native species, considering the various reports on geographical venom variations. Since antivenom is the only definitive treatment for snake envenomation, essentially, the effectiveness of venom neutralization relies on the molecular characteristics and antigenic determinants of the venom toxins. Considerable compositional, syndromic and immunological variations have been reported for the venoms of several cobra taxa, including those which are sympatric.