Paraspecific neutralization of the venom of African species of cobra by an equine antiserum against Naja melanoleuca: A comparative study

Venoms of snakes belonging to the same Genera tend to share biochemical, toxinological and antigenic characteristics. Accordingly, paraspecific neutralization of venom lethality by experimental antisera and commercial antivenoms has been reported. We studied the spectrum of neutralization of lethality of an experimental monovalent equine antiserum against the strongly neurotoxic African forest cobra (Naja melanoleuca) when tested against venoms of most species of African Naja, both neuro and cytotoxic as described by some authors. We report a comparison of the median lethal doses (LD50) of the venoms and the paraspecific median effective doses (ED50) of the antiserum calculated using three methods: Spearman–Kärber and Probit (currently recommended by the World Health Organization), and non-linear regression. An ample – but not complete – spectrum of paraspecific neutralization of lethality was observed against both spitting and non-spitting species of African Naja with a clearly more efficient neutralization of the more potent venoms, the implications of which are discussed. The median lethal and effective doses calculated by the three methods are remarkably consistent and may warrant consideration of non-linear regression methods for the calculation of venom lethality and antivenom potency by venom/antivenom researchers and producers.