Pit Viper Snakebite Envenomation in the United States

Successful treatment of crotalid-induced neurotoxicity with a new polyspecific crotalid Fab antivenom

STUDY OBJECTIVE

To report the effectiveness of a new polyvalent crotalid antivenom on neurotoxicity associated with North American rattlesnake envenomation. Two syndromes of crotalid-induced neurotoxicity have been reported. In severe envenomation by Crotalus scutulatus scutulatus (Mojave rattlesnake), weakness and fasciculations of various muscle groups, including those innervated by cranial nerves, may develop. Occasionally respiratory insufficiency develops. The second neurotoxic effects is myokymia, a type of fasciculation most frequently reported after bites by Crotalus horridus horridus (timber rattlesnake) and Crotalus atrox (Western diamondback rattlesnake). Conventional polyvalent antivenom is often ineffective in the treatment of venom-induced neurotoxicity.

METHODS

We report a case series of three patients envenomated by North American rattlesnakes, one of which was identified as C scutulatus scutulatus. All three patients experienced neurotoxicity with weakness, paresthesias, and dramatic fasciculations, along with other signs and symptoms of crotalid venom poisoning.

RESULTS

The administration of new polyspecific crotalid antivenom made of ovine Fab was successful in immediately and completely reversing neurotoxicity in each of these patients.

CONCLUSION

We report the use of a new antivenom for North American crotalid envenomation that seems to have efficacy in reversing neurotoxicity associated with these bites.

Rattlesnake and scorpion antivenoms from the egg yolks of immunized hens

Antivenoms used to treat poisonous bites and stings are usually derived from horse sera. Consequently, they contain horse immunoglobulins, which frequently cause complement mediated side effects, and other proteins that can cause serum sickness and, occasionally, anaphylactic shock. Here we describe a new, avian source of antivenoms that precludes these complications, and an efficient and gentle means for preparing antivenoms composed solely of venom-specific antibodies. We demonstrate that antivenoms purified from the egg yolks of laying hens immunized with Crotalus atrox rattlesnake venom and Leiurus quinquestriatus hebraeus scorpion venom neutralize the lethal effects of these venoms in vivo. Antivenoms purified from chicken eggs may be pharmaceutically safer and more economical to produce than current horse antivenoms.

Mechanism of defibrination in humans after envenomation by the Eastern diamondback rattlesnake

We prospectively studied the hemostatic system of ten persons bitten by the Eastern diamondback rattlesnake (Crotalus adamanteus) during 1978-1980. Blood was drawn when the patients arrived in the emergency room and every 6 hr thereafter. All envenomated victims developed incoagulable blood (defined by a thrombin time greater than or equal to 120 sec, normal less than 20 sec). Platelet counts and plasma levels of antithrombin III and factors II and VIII were not drastically altered, which distinguished this disorder from classic disseminated intravascular coagulation. Fibrinogen levels were markedly decreased (mean coagulable level of 0 mg/dl and antigenic levels of 99 mg/dl). Plasminogen levels were 20% of normal, alpha-2-plasminogen inhibitor was 17% of normal, and plasminogen activator was 20 times normal. Levels of fibrin degradation products peaked at a mean of 7,680 micrograms/ml. The magnitude and duration of the coagulopathy were proportional to the clinical severity of envenomation. Treatment with antivenin blunted the coagulopathy. Because venom from the Eastern diamondback rattlesnake does not directly activate plasminogen, we conclude that coagulopathy following envenomation by that reptile appears to be due to partial proteolysis of fibrinogen with secondary activation of plasminogen by released plasminogen activator, probably of endothelial origin.