Carpet Viper (Echis romani) Envenoming in Nigeria: Ecology, Venom Pathophysiology, Clinical Burden and Health-System Determinants

Abstract

The carpet viper (Echis romani, recently separated from E. ocellatus) accounts for at least 66% of confirmed snakebite envenomings in the Nigerian savanna. Despite this, continental hazard modeling ranks it second in Nigeria. It is smaller and not necessarily more venomous per bite than the puff adder (Bitis arietans) or the black-necked spitting cobra (Naja nigricollis). This review synthesizes evidence on the ecology, venom effects, clinical impact, and health-system factors of carpet viper envenoming in Nigeria, including its effects on livestock and One Health considerations. The risk of snakebite is influenced by multiple factors beyond venom potency alone. Carpet vipers are common in farmland and rural areas, where farmers, herders, and children are at risk. Their camouflage and defensive strikes increase the chances of accidental bites. Their metalloproteinase-rich venom can cause coagulopathy, bleeding, tissue damage, shock, and death if left untreated. While case fatality has decreased to approximately 1.4–1.5% at specialized centres with effective antivenom, this progress is fragile due to delayed presentation, limited rural healthcare, and inconsistent antivenom availability. Evidence regarding livestock is limited; although animals share the habitat, bites are rarely documented. Promising small-molecule toxin inhibitors are not yet validated for E. romani. Climate and land-use models suggest habitat changes may alter snake distribution. Carpet viper envenoming is a major and preventable cause of snakebite morbidity and mortality in northern Nigeria. Current evidence supports sustained investment in antivenom supply, rural diagnostic capacity (including the 20-minute whole-blood clotting test), referral pathways, community prevention, rehabilitation and standardized, species-confirmed surveillance.