Experimental assessment of a new, low-cost antivenom for treatment of carpet viper (Echis ocellatus) envenoming.

Morbidity and mortality due to envenoming by the carpet viper (Echis ocellatus) in northern Nigeria remains unacceptably high and constitutes a severe economic and public health problem to the local farming community in particular. The only effective treatment of systemic envenoming is antivenom, but supplies are very limited as the little that is available is either too expensive, ineffective or both. Here, we describe a new ovine antivenom, designed both to be effective and to be available at low cost. The antivenom, a polyclonal ovine Fab preparation, provides superior protection, both in vivo and in vitro, to the best alternatives, the monospecific South African Institute of Medical Research antivenom and the polyspecific Pasteur Isper Africa antivenom. Fab fragments, which have the advantages of large volumes of distribution and, theoretically, low immuno-reactivity, are produced by a reusable solid-phase papain matrix which eliminates enzyme contamination of the product and reduces cost. The antivenom is lyophilised for increased stability and extended shelf-life in tropical climates where it is often impossible to keep such products cool.