Snake Bite in India: A Brief Overview

by Dr V. V. Pillay, Amrita Institute Of Medical Sciences & Research Centre, Cochin, India

Introduction

In India, the annual mortality from snake bite is said to be between 25,000-30,000. More than 2000 deaths per year are reported from the state of Maharashtra alone. This may actually be much less than the real number, since the majority of snake bite deaths go unreported, as many villagers go to traditional healers who do not report any cases to the authorities, nor do they generally even maintain any records of their patients. Moreover, snake bite is unfortunately not a notifiable illness, and therefore even allopathic physicians working in small clinics or peripheral areas do not report such cases.

Among the challenges faced in improving snake bite treatment and reducing morbidity and deaths, is the low priority given to the problem by government. For example, the Health Dept functioning under the Central Ministry allocates an annual grant for snake bite that is many times less than the grant allocated for amoebic dysentery (which has negligible fatality as compared to snake bite). Consequently research in this area has neglected, and there are few Indian scientists carrying out authentic research in this field.

India's Venomous Snakes

There are about 216 species of snakes in India, of which 52 are known to be venomous. The major families of venomous snakes in India comprise elapids (cobra, king cobra and kraits) viperids (Russell’s viper, saw scaled viper or carpet viper, and pit vipers), and hydropids (sea snakes). Among the most important species from a medical perspective are:

Cobras

With the exception of the king cobra (Ophiophagus hannah) Asiatic cobras belong to a single genus: Naja. Four species are found in India: Naja naja (common Indian cobra, spectacled cobra) is seen throughout the country, Naja kaouthia in the east and the north east regions, Naja oxiana in the extreme north-west region, and Naja sagittifera in the Andaman islands. Most adult cobras measure 100-150 cm, though specimens measuring up to 220 cm have been reported. The Indian spectacled cobra is very variable in colour. Often the colour of the cobra matches with the soil of the region it inhabits, and may be brown, reddish, grey, or black. It is easily recognized by its hood which has a characteristic spectacle mark on the dorsal surface. Occasionally there may only be a ‘monocle’ mark.

Cobras are found in a variety of habitats, but are especially common in agricultural fields: sugarcane, paddy, soybean or jawar. Many cobra bites occur among farmers and their families living in mud houses near such fields; the snake may be encountered among rubble in the attic, or among firewood, etc. Many a time, the snake enters the cages of hens often located near the corner of a hut. Since rats flourish in and around grain bags stored in these houses, and especially in granaries, cobras are often seen in such places, and many accidental bites occur among humans handling these bags. Jawar (sorghum) breads or chapattis are often kept in baskets near windows in mud walled huts, and rats invade the basket leading snakes to follow them. Bites occur when the housewife blindly puts in her hand to take out the chapattis.

In recent times, due to severe power shortage in some states such as Maharashtra, snakebite cases have shot up sharply due to long periods of electric load shedding in villages leaving these in darkness much of the time.

Krait

The common krait or Indian krait (Bungarus caeruleus) is said to be the most venomous of all the species of snakes seen in India. The common krait is a relatively small snake (30-120 cm) with the head slightly broader than the neck; eyes have round pupils. The color of the snake is usually glossy black, bluish gray or brownish black with narrow (often paired) white bands all across the back that continue to the tip of the short tail. These bands may be absent proximally, where they are replaced by white vertebral spots. The non-venomous wolfsnake, which resembles the krait, on the other hand has bands right from the beginning of the head, but may be absent towards the narrow long tail.

Kraits are mostly nocturnal. During the daytime they may rest in termite mounds, rodent burrows, piles of brick, heaped coconuts or firewood, cowdung, and sometimes within the house underneath beddings or pillows. Kraits are known to enter human dwellings quite commonly in search of prey. Even in proper concrete houses, kraits can enter via the drains of the bathroom if these are not closed with grating.
The maximum incidence of krait bite is said to be during the monsoon months, probably because due to heavy rain, the holes where rats and other rodents dwell get filled with water. Also due to the cold and wet weather, the snakes may enter human dwellings to take advantage of the shelter and warmth. Majority of the bites occur between 11 PM and 5 AM. Since there is not much pain associated with a krait bite, the sleeping person may not even realize he was bitten by a snake when he wakes up in the morning. The ensuing neurological symptoms and signs may in fact be mistaken for a cerebral stroke.

Russell’s viper

Russell’s viper (Daboia russelii: previously Vipera russelii) is commonly seen in many parts of India, and even neighbouring coutries such as Pakistan, Sri Lanka, Bangladesh, and Myanmar. It is generally 90-150 cm long, with a stout and rough-scaled body. The head is triangular and much broader than the neck. Nostrils are relatively large, and the eyes have vertical pupils. The colour of this snake is generally brown or yellowish brown. There are three rows of large brown or black, oval or round spots along the entire back. The spots may have pointed ends, to form a chain like pattern, or the margins may be rimmed with white or cream colour. The head usually has a narrow, inverted ‘V’ shaped mark.

This snake is nocturnal. It is often encountered in grassy areas, forest edges, rocky hillocks, and dense scrub vegetation. Most of the bites are reported during harvest time.

When disturbed, it hisses loudly “like a pressure cooker” and only bites as a last resort. The fangs are long, and rotate backwards against the roof of the mouth when it is closed.

Saw scaled viper

The saw scaled viper (Echis carinatus) is a small snake, growing up to 30-90 cm in length. The head appears more rounded than triangular, while the rest of the body is cylindrical, short, and stout. It has large eyes with vertical pupils. The tail is very short. The entire body is covered with rough, serrated scales. This snake is usually pale brown in colour, with dark brown, brick red, or gray zigzag patterns on the back. An arrowhead-like or bird foot-like mark is present on the head.

The saw scaled viper is mainly nocturnal. It frequents open dry, sandy, or rocky plains and hills. It often rests under rocks, or at the base of shrubs or trees during the day. The quickness with which it bites on smallest provocation, with an extremely rapid strike makes it one of the most dangerous snakes. When disturbed, it forms a double coil in the form of the figure 8, with its head in the center ready to strike. The coils are rubbed against each other, and the serrated scales produce a grating or rasping sound.

Pit vipers

Various kinds of pit vipers are found in hilly areas, or forests in most parts of the country. The Western Ghats and the Malabar region of Kerala abound in these snakes. Often they are encountered near low bushes, or stream edges. Accidental bites occur while plucking flowers or berries. While most pit vipers are not very venomous, the hump-nosed pit viper (Hypnale hypnale) of Kerala has been known to cause deaths.

Sea snakes

Sea snakes are encountered in all the coastal regions of India. They often land in the nets of fishermen. While the venom is quite potent, deaths due to sea snake bite are quite rare.

Snake Venom

Different species of snakes inject different volumes of venom when they bite, and the toxicity of the venom produced by each species can vary a great deal. Antivenom dosing recommendations are based on the quantity of a particular venom [in milligrams (mg), dry weight] that can be neutralized by each milliliter (ml) of antivenom. The half life of Indian ASV is said to be 26-95 hours. In India, each milliliter of a polyvalent antivenom is supposed to neutralize:

• 0.6 mg of Indian cobra (Naja naja) venom;
• 0.6 mg of Russell’s viper (Daboia russelii) venom;
• 0.45 mg of Common krait (Bungarus caeruleus) venom; and
• 0.45 mg of Saw scaled viper (Echis carinatus) venom.

The average venom yield of these species are:

• 200 mg for Indian cobra (Naja naja);
• 150 mg for Russell’s viper (Daboia russelii);
• 22 mg of Common krait (Bungarus caeruleus) venom; and
• 4.6 mg of Saw scaled viper (Echis carinatus) venom.

The amount of venom that may be fatal to humans varies from one species to another. Literature reports suggest that the lethal doses of these four species are about:

• 120 mg for Indian cobra (Naja naja);
• 150 mg for Russell’s viper (Daboia russelii);
• 60 mg of Common krait (Bungarus caeruleus) venom; and
• 80 mg of Saw scaled viper (Echis carinatus) venom.

High incidence of snakebite is reported during the summer and the rainy season.

Causes for high mortality from snakebite in India

1. A majority of snakebites occur in rural parts of the country where good roads and motor vehicles are a rarity. Transporting a snakebite victim in time to the nearest medical clinic or hospital is therefore difficult.
2. Many cases of snakebite are attended to by traditional or faith healers, who do not employ antisnake venom therapy, but instead resort to extremely unscientific herbal and other exotic remedies. Unfortunately, even the practitioners of alternative systems of medicine (such as Ayurveda, Unani or Siddha) which are quite popular, do not often utilize antivenom. Many of these healers and practitioners advocate dangerous or useless first aid measures such as tight (sometimes multiple) tourniquets, “snake stones”, etc., which enhance the chances of serious morbidity and mortality.
3. Even though there are Govt. Primary Health Centers (PHCs) in many villages, most of them are under-staffed (especially with regard to doctors), and under-equipped. Antisnake venom (ASV) being costly is rarely available, and emergency equipment such as laryngoscopes, endotracheal tubes, Ambu bags, ventilators, etc., are also often unavailable. Even if a PHC has a doctor on the rolls, he is most often a freshly passed-out graduate, who may not have seen or treated cases of snakebite during his training period.
4. The Indian medical curriculum (undergraduate as well as postgraduate) does not place sufficient emphasis on the management of poisoning or envenoming.
5. Because ASV is expensive it is not easily available in Govt hospitals, while at private hospitals, many doctors avoid admitting snakebite cases due to the fear of anaphylaxis. Moreover, poor rural folk cannot afford expensive ASV treatment at private hospitals.

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