Snakebite by the Shore Pit Viper (Trimeresurus purpureomaculatus) Treated With Polyvalent Antivenom

Although snakebites are uncommon, there are several species of medically important venomous snakes native to Singapore. We present a case of envenoming by the shore pit viper (Trimeresurus purpureomaculatus) that showed clinical improvement when treated with the Indian (Haffkine) polyvalent antivenom. A 40-year-old man was bitten on his right hand by a snake, which was identified through photos and his description to be a shore pit viper, which is native to the local mangrove area. Severe swelling and pain developed immediately after the bite, which progressed up the arm. Because of the progression of local swelling, antivenom was started. He was given a total of 6 vials (60 mL) of polyvalent antivenom, with the first vial started 3 hours after the bite. He showed clinical improvement within 24 hours. His subsequent recovery was uneventful, with no other complications as a result of envenomation or antivenom use. Severe envenoming by the shore pit viper can lead to marked local effects such as extensive swelling and tissue necrosis. Antivenom is indicated in the presence of severe local envenomation. Antivenom against the shore pit viper is however not available locally. The Indian (Haffkine) polyvalent antivenom contains antibodies against 4 common venomous snakes in India, namely the Indian cobra, common krait, Russell's viper, and sawscaled viper. The improvement seen in this patient suggests possible cross-neutralizing activity of the Indian vipers' antivenom against the local shore pit viper venom. Further in vivo and in vitro studies should be performed to verify this clinical case.