Clinical manifestations of alpine pit viper (Trimeresurus gracilis) bites

Introduction: The alpine pit viper, Trimeresurus gracilis, is an endemic species in Taiwan. The incidence of human envenoming is rare.

Case summaries: We present three events in two patients bitten by Trimeresurus gracilis. In the first patient, envenoming inflicted pain, local bleeding, hemorrhagic bulla, and progressive swelling, leading to necrosis of the bite wound. In the second patient, the two snakebites caused pain and progressive swelling. There were no systemic effects such as organ damage or neurological deficits observed. A paraspecific antivenom against Trimeresurus stejnegeri and Protobothrops mucrosquamatus was used to treat both patients, with a favorable outcome in each.

Discussion: Combined with the clinical manifestations of two previously reported cases of Trimeresurus gracilis envenoming, the known effects of Trimeresurus gracilis venom in humans include local toxicities, severe soft-tissue damage, compartment syndrome, and coagulopathy without spontaneous systemic bleeding. The paraspecific antivenom, which has demonstrable cross-neutralization effects in animal studies, appeared to be effective against the local toxicities as the patients showed prompt cessation of the progression of their swelling.

Conclusions: The knowledge of clinical manifestations and management approaches to Trimeresurus gracilis envenoming is helpful for patient care. The use of the paraspecific antivenom should be considered in managing such envenoming.