Neutralization of the lethality of the venom of Dendroaspis polylepis (black mamba) in mice by two polyvalent antivenoms used in Kenyan hospitals: Results of a 2009–2011 study

The black mamba is a common snake in Sub-Saharan Africa, a region with a high burden of snakebite envenoming. Differences in the composition and toxicity of the venom of this snake as one moves from one region to another within Sub-Saharan Africa, and the variations in manufacturing protocols by different antivenom producers may result in antivenom products of unknown efficacy. This variability may compromise the management of venomous snakebite in the region including those of the black mamba. Therefore, testing the antidotal efficacy of the antivenoms indicated for black mamba venom is warranted. The aim of the present study was to determine the efficacy of two antivenoms routinely used in some hospitals in Kenya between 2009 and 2011.The moving average interpolation method of Weil was used to determine the acute intraperitoneal (i.p) median lethal dose (LD50) of black mamba venom in mice. Symptoms of envenomation and the effects of the venom on hematological parameters were observed. The antidotal efficacy of the two polyvalent antivenoms (antivenom I and II) was then tested against the acute i.p. LD50 of black mamba venom.The acute i.p. LD50 of the whole venom of black mamba in mice was found to be 0.341 mg/kg. Antivenom I afforded 80% protection to mice experimentally envenomed with a 3 LD50 dose of black mamba venom while antivenom II afforded 60% protection to mice experimentally envenomed with a 3 LD50 dose of black mamba venom. Additionally, antivenom II also afforded 40% protection to mice experimentally envenomed with a 4 LD50 dose of black mamba venom. Analgesia, weakness, and altered respiration were observed as neurotoxic symptoms.The LD50 of black mamba venom in mice by the intraperitoneal route is low. Moreover, the data also suggests that the antivenoms tested during the study period had varying efficacy in neutralizing black mamba envenomation in mice. Keywords: Snakebite, Snakebite envenoming, Black mamba, Dendroaspis polylepis, Lethality, Antivenom, Kenya