POISONING BY BITES OF SAW-SCALED OR CARPET VIPER (ECHIS-CARINATUS) IN NIGERIA

  • 1 January 1977
    • journal article
    • research article
    • Vol. 46  (181) , 33-62
Abstract
The Saw-scaled or Carpet Viper (E. carinatus) whose range extends from Senegal to Bengal probably bites and kills more people than any other species of snake. Patients (115) with poisoning caused by its bite were studied in the savanna region of Nigeria, where victims of this snake may occupy 10% of hospital beds. Patients showing no signs of envenoming were excluded. All patients had local swelling at the site of the bite. Other features included local blistering (13%), local necrosis (11%), incoagulable blood (93%) and spontaneous systemic bleeding (57%). There was evidence of disseminated intravascular coagulation in all cases; fibrinogen was severely depleted, fibrin degradation products were increased (mean 1711 .+-. 904 .mu.g/ml), but significant thrombocytopenia (< 103,000/mm3) was seen in only 10 severe cases. Clotting factors V, VIII, II and XIII were depleted, while X and VII were usually normal. Fibrinolytic activity was rarely increased, so it seems likely that a procoagulant action (direct activation of prothrombin) is the principal effect of E. carinatus venom on blood coagulation in man. Development of the hemostatic defect was observed as early as 75 min and as late as 27 h after the bite. Spontaneous hemorrhage is clinically the most important effect of E. carinatus venom, causing the 5 deaths in this series. The relative importance of procoagulant and hemorrhagic components of the venom in causing hemorrhage is discussed. Complement activation via the classical and alternative pathways may have contributed to vascular damage. Mortality was reduced from the untreated level of between 10-20% to 2.8% in a group of 107 patients treated with 10-110 ml of specific antivenom. The dose was controlled using a simple clotting test. Blood coagulability was restored in 2-39 (mean 12) h after the 1st dose of antivenom. Immediate-type serum reacitons were observed in 21% of cases. Additional treatment included blood transfusion for patients in hemorrhagic shock and early surgical debridement of necrotic tissue at the site of the bite.