SOUTH AMERICAN COLUBRID ENVENOMATIONS

Most snakebites in South America are caused by pitvipers (Bothrops, Crotalus and Lachesis spp.) and coral snakes (Micrurus spp.), with less serious accidents caused by colubrids. Rear-fanged species are responsible for most colubrid envenomations, the principal genera involved being Clelia, Helicops, Liophis, Philodryas, Tachymenis, and Thamnodynastes. The hands, feet and upper and lower limbs are bitten most frequently. Most envenomations are mild, involving mainly local pain, edema and ecchymosis. Systemic envenomation (altered whole blood clotting time, systemic bleeding, shock, and renal failure) is rare and only one fatality suspected to have been caused by a colubrid (P. olfersii in Brazil) has been recorded. Treatment is symptomatic and supportive, and recovery is generally uneventful, with no sequelae. The similarity between the local effects of envenomations by colubrids and those produced by South American lanceheads (Bothrops spp.) has resulted in bothropic antivenom being administered in several cases, but there is little conclusive evidence that antivenom enhanced the patients' condition. Together, these findings indicate that envenomations by South American colubrids are considerably less serious than those reported for certain African and Asian colubrids (Boiga, Dispholidus, Rhabdophis and Thelotornis spp.). However, the limited number of species involved in human envenomations to date compared to the large number of South American colubrids currently recognized suggests the need for caution in generalizing about the potential seriousness of bites by species not yet implicated in such accidents.