Epidemiology and clinical profile of cobra (Naja naja) envenomation in wet zone of Sri Lanka

Abstract

Cobra (Naja naja) is widely distributed in Sri Lanka, but its bites are less common compared to viper bites. Its envenoming could be deadly due to neurotoxicity and severe local tissue necrosis. We describe a series of 12 patients with cobra bites in the Provincial General Hospital, Ratnapura, Sri Lanka over two years from October 2013. Of the 12 bites, offending snakes were available in 5 (41.6%) cases for identification and in the rest patients have identified cobra as the responsible snake. There were 8 (66.6%) males and 4 (33.3%) females including a pregnant mother of 37weeks gestation. The age of these patients ranged 17-72years. All bites occurred during day time (9am-6pm). The bitten sites were hands (5; 41.6%), feet (4; 33.3%), legs (2; 16.6%) and face (1; 8.3%). Four (33.3%) patients were bitten indoors, 3 (25%) while working at home gardens, 2 (16.6%) while working in tea estates and walking on foot paths and 1 (8.3%) while working in a paddy field. Four (33.3%) patients had dry bites and 8 (66.6%) had envenoming. Of envenomed patients 6 (50%) patients developed neurological signs. Five had ptosis, double vision and ophthalmoplegia, 3 had respiratory failure and 2 had dysphagia. Four (33.3%) patients developed coagulopathy (positive -whole blood clotting test, PT and aPPT) and myotoxicity (muscle pain and tenderness) whereas 3 (25%) had local tissue necrosis. Local effects were pain (11; 91.6%), swelling (8; 66.6%) and bleeding (3; 25%). Two patients (16.6%) needed ICU care and 2 died. Antivenom serum (AVS) was administered to 7 (58.3%) patients of them 4 (57.1%) developed allergic reactions. We observed coagulopathy which was not a well established manifestation in cobra envenoming. But in order to confirm this, there should be a toxin analysis regarding cobra venom. With the occurrence of coagulopathy and low incidence of local tissue necrosis suggests possible geographical variation of venom composition.