Snake Epidemiology

Snake   Epidemiology
Snakes are distributed throughout most of the earth's surface with some exceptions such as the Arctic, Antarctic, and many small islands. Snakes are poikilothermic carnivorous reptiles that have evolved the venomous apparatus for the purpose of procurement of food. [9] To a large extent the manifestation of snakebite depends upon the species of snake, and therefore identification of the type of snake is paramount. At times the bite mark might not be visible (e.g., in the case of krait). The killed snake brought as evidence helps in identification of snake, in which case species-specific monovalent Anti snake venom (ASV) can be administered. The clinical manifestations of the patient may not correlate with the species of snake brought as evidence. it is therefore advantageous to know the appearance of the snake so as to recognize the species.
The three major families of venomous snakes are the Elapidae, the Viperidae, and the Hydrophidae.


Elapidae

      Elapidae (cobra, king cobra, krait, and coral snake): These snakes have heads that are of about identical width as their necks. The head is bathed in large scales but lack laureal shields. Their pupils are round and they are oviparous. These snakes have grooved fangs that are short, fixed, and covered by mucous membrane. They, therefore, cannot bite through clothes and sometimes deliver only a sublethal dose.



Viperidae 

     Viperidae (vipers): The head of a viper is triangular, wider than the neck, and has laureal shields. They have vertically elliptical pupils and are ovi-viviparous. Their fangs are long, movable, and canalized like hypodermic needles. they're further subdivided into pit viper and pitless viper subfamilies. The Crotalinae (pit vipers) have a special sense organ, the pit organ, to detect their warm-blooded prey. This is situated between the nostril and the eye. The rattlesnake belongs to the pit viper subfamily, while the Russell's viper and the saw-scaled viper belong to the pitless viper subfamily.
Hydrophidae
        Hydrophidae (sea snake): Sea snakes are found in the vicinity of the seacoast. They have a tiny head and a flattened tail that helps them swim. Though venomous, they seldom bite.

In India, more than 200 species of snakes have been identified but only 52 are poisonous; the common krait (Bungarus caeruleus), Indian cobra (Naja naja), Russell's viper (Daboia russelii), and saw-scaled viper (Echis carinatus) are the most poisonous ("the big four"). In the Indian setting, nearly two-thirds of bites are attributed to saw-scaled vipers, about one-fourth to Russell's viper, and only a little proportion to cobras and kraits.



Host and environmental factors
Thorough statistical analysis of snakebite is difficult and the available data is not always complete because of the varied distribution (and because most bites occur in remote villages). Snakebite may be termed an occupational disease, as farmers, plantation workers, herdsmen, hunters, or workers on growth sites are mostly affected. Snakebites show a classical seasonal variation, being more common in summers and in the rainy season, when it's associated with agricultural activities. The majority of snakes dont bite without provocation; most bites are inflicted when the snakes are inadvertently trodden upon. Males are bitten almost twice as sometimes as females, with the majority of the bites being on the lower extremities. Fortunately, 50% of bites by venomous snakes are "dry bites" that result in negligible envenomation. The percentage of dry bites ranges from 10-80% for various poisonous snakes.



   Conclusion
Snakes do not generally attack human beings unless provoked. However, once bitten, a wide spectrum of clinical manifestations may result. The emphasis should be on early and adequate medical management. Delayed medical management and lack of public awareness results in prolonged hospital and ICU stay of the patients. This can be decreased if regular public programs regarding prevention, prehospital management (first aid), and the importance of early transfer to hospital are conducted.
Overemphasis on reducing the load of snake venom in the victim during prehospital management can be dangerous because its role is debatable and too much valuable time is wasted in its administration. Most of the traditional methods for first aid treatment of snakebite, both western and "traditional/herbal," have been found to result in more harm than good. Identification of the species of snake sensible for the bite is very important for optimal clinical management. Antivenom is the only efficient antidote for snake venom. However, it's costly and sometimes in short supply and its use carries the risk of potentially dangerous reactions.