Snake bite is a common emergency seen in almost all parts of India and the rural parts of west and central Africa. Most of the bites occur in persons while engaged in agricultural operations or while walking in darkness. Snakes are found more frequently around dwelling houses, embankments, cultivated fields and in bushes.They tend to frequent places where they get their prey-rodents and frogs. Most of the bites take place in the rural areas though they do occur in towns also. About 15 to 29 thousand deaths occur in India due to snake bite annually. Most of the poisonous bites (8%) are due to vipers Vipera russelli and Echis Carinatus), Cobras (Naja naja) cause 10% and kratis (Bungarus caerulus) 4%. Rarely, poisoning due to sea snakes in encountered (1%). Majority of bites are inflicted by non-poisonous snakes. The incidence of snake bites varies with the season in different regions.
Identification of Poisonous snakes
1. They have large ventral scales covering the whole of the ventral aspect.
2. The mouth contains only one pair of poison fangs in the upper jaw-placed anteriorly (krait and Cobra) or posteriorly (Viper).
3. Presence of small teeth is characteristic of non-poisonous snakes.
The head is triangular with a narrow neck. The scales on the body and neck are small and of uniform size. Vipera russelli is larger, often grows to one meter in length and shows three rows of oval rings on the body, running along the whole length.
Echis carinatus has overlapping saw-shaped scales covering its body and a broad arrow mark on its head and two rows of wavy bands running longitudinally. Pit vipers belonging to the family Crotalidae are less common in India. They show a depression between the nose and the eye, the loreal pit. Vipers have larger fangs which are tunneled and the bite marks are more prominent. Often the snake hangs on to the limb and it has to be disentangled by violent movements.
Cobra has an expandable neck and the head shows a single (monocellate) or double (binocellate) dark ring on the dorsum. The third suprelabial shield touches the eye and nostril. When provoked, the head and neck are raised to form the hood. The fangs are small and anteriorly grooved. Rarely, King cobras (Naja hanna or Hand-yard) may be seen in thick forests but bites by these deadly snakes are very uncommon. They grow to large sizes (often 3-4 meters0 and unlike the cobra, they are unhooded.
Kraits show white bands on the body: Those in the posterior part being more definite. The dorsal scales on the body are hexagonal. The head and the sides of the lower jaw are covered with large shields, the fourth shield on the lower jaw being the largest.
Sea snakes are found in good numbers in the coastal waters of India. They show laterally compressed and flattened tails. Snakes bite when they are inadvertently trodden upon. Rarely, Cobras may attack but they usually do so during the mating season.