Envenoming by viper bites in France: clinical gradation and biological quantification by ELISA

Viper bites are frequent in France but the evaluation of the severity of envenomings and consequently patient treatment has not yet been properly evaluated. The purpose of this study was to measure venom antigens in blood and/or urine of bitten patients and to establish a quantitative relationship with clinical observations. A prospective enquiry was conducted in 1990 in France to collect epidemiological, clinical and biological data from hospitals. Urine and blood samples were tested for their content of Vipera aspis venom antigens by a sandwich enzyme linked immunosorbent assay (ELISA). One hundred and two charts were analysed, from patients presenting documented viper bites. Oedema was the prominent local feature (81 cases). Systemic signs consisted of vomiting and/or diarrhoea (22 cases), slight or severe hypotension (15 cases), shock (2 cases) and bleeding (1 case). A relationship was observed between these systemic signs and the extent of the oedema, which permitted the establishment of a grading scale. Grade 0 (no envenoming) was identified by fang marks and absence of oedema and local reaction; grade 1 (mild envenoming) by local oedema and absence of systemic symptoms; grade 2 (moderate envenoming) by regional oedema and moderate systemic symptoms; and grade 3 (severe envenoming) by extensive oedema and severe systemic symptoms. Quantification of venom antigens in blood or urine of patients by ELISA revealed a significant correlation between clinical signs of envenoming and the level of venom antigens in blood or urine. This indicated that the ELISA test is a useful and predictive tool for clinically grading viper envenomings.