A 42-year-old gardener is bitten on the hand by a snake while clearing vegetation. Within an hour the bite site shows intense local pain, rapidly progressive swelling, haemorrhagic bullae, and darkening of skin suggestive of early necrosis. Six hours later he develops drooping of both eyelids and difficulty lifting his head. The snake responsible most likely is:

• A Saw-scaled viper (Echis carinatus)
• B Common krait (Bungarus caeruleus)
• C Russell's viper (Daboia russelii)
• D Spectacled cobra (Naja naja) ✓

Explanation

The combination of prominent local cytotoxicity (pain, swelling, bullae, necrosis) together with delayed onset neuromuscular paralysis is classical of cobra envenomation, whose three-finger toxins are postsynaptic and whose cytotoxins destroy local tissue. Kraits produce negligible local changes at the bite site, while both vipers cause coagulopathy and bleeding rather than ptosis. Local necrosis therefore excludes krait, the strongest distractor, because pure neurotoxicity without local signs points away from it.

Reference: WHO Guidelines for the Management of Snakebites, South-East Asia Region, 2nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.