The list of venomous snakes around the world includes:

American Copperhead
Bushmaster
Coral Snake
Cottonmouth
Eastern Diamondback Rattlesnake
Eyelash Pit Viper
Fer-De-Lance
Jumping Viper
Mojave Rattlesnake
Tropical Rattlesnake
Western Diamondback Rattlesnake
Common Adder
Long-Nosed Adder
Pallas’ Viper
Ursini’s Viper
Boomslang
Bush Viper
Common Cobra
Egyptian Cobra
Gaboon Viper
Green Mamba
Green Tree Pit Viper
Habu Pit Viper
Horned Desert Viper
King Cobra
Krait
Levant Viper
Malayan Pit Viper
Mcmahon’s Viper
Mole Viper or Burrowing Viper
Palestinian Viper
Puff Adder
Rhinoceros Viper or River Jack
Russel’s Viper
Sand Viper
Saw-Scaled Viper
Wagler’s Pit Viper or Temple Viper
Australian Copperhead
Death Adder
Taipan
Tiger Snake

Snake-Fang Evolution Mystery Solved -- "Major Surprise"

Biologist Freek Vonk goes eye to eye with the longest venomous snake species in the world—a female king cobra—in the Indonesian rainforest.

James Owen
for National Geographic News

July 30, 2008

The diverse and deadly array of venomous snakes living today all arose from a single fanged ancestor, a new study suggests.

Vipers, cobras, and other snakes that have fangs at the fronts of their jaws surprisingly begin life like snakes that have poisonous fangs at the back of their jaws, said a team led by Freek Vonk of Leiden University in the Netherlands.

The discovery suggests venomous fangs—the lethal evolutionary invention that led to snakes becoming so successful—arose only once about 60 million years ago.

The origins of venom-injecting snakes have long been the source of scientific controversy, because the contrasting fang positions of diverse snake groups pointed to independent evolution.

But a study of the embryos of eight front- and rear-fanged species has found that fangs always first appear at the back of the upper jaw before migrating forward in vipers and cobras.

This previously unidentified transformation in the unborn young occurs due to "rapid growth of some parts of the upper jaw relative to the others," Vonk explained.

Single Origin

"It's a major, major surprise," the zoologist said of the findings, which will appear tomorrow in the journal Nature.

"There was no significant evidence before for such a single origin of fangs."

Furthermore, the team may have identified the prehistoric mechanism that allowed snake fangs to develop from teeth.

The findings suggest the rear of part of the reptiles' tooth-forming layer in the upper jaw long ago became uncoupled from the rest of the jaw, enabling the back teeth to evolve independently with the venom gland.

"This uncoupling idea is totally new," Vonk said.

"Snakes evolved the fangs once, probably by an uncoupling between some rear and front teeth, and then after that they just played with the [fang] position within the embryo."

This theory makes absolute sense from an evolutionary standpoint, he added, since snake fangs are unique among vertebrates.

"It would be very difficult to assume that snakes had miraculously invented fangs at different occasions," Vonk argued.

The jaw uncoupling may have occurred as far back as 60 million years ago, "at the base of the advanced snake tree."

Venom Systems

After that, Vonk added, "the different lineages could evolve their highly sophisticated venom systems."

Of the 3,000-odd snake species living today, advanced snakes (which are nearly all venomous) number around 2,700, he noted.

Johannes Müller, a reptile fossil expert and curator at the Museum für Naturkunde in Berlin, Germany, said, "I think this is a very important study which, from a novel perspective, sheds new light on our understanding of advanced snake evolution.

"The study shows that advanced snakes seem to share a common, and highly modified, developmental mechanism in the upper jaw," said Müller, who wasn't involved in the new study.

"It supports the view that the developmental tool kit for becoming venomous evolved only once, and the different advanced snake lineages then took advantage of it in various ways," he added.

Modern Myths About Snakes

Below is a list of common myths regarding snakes and snake behavior and some possible explanations for these tales.


Charming Snakes
A popular myth about snakes is that they are somehow able to hypnotize or "charm" their prey so that the prey is unable to escape. There is no evidence to support the claim that snakes charm their prey. This myth may have resulted from the observation of small animals and birds becoming "frozen with fear" when confronted by snakes, however they are not being charmed. Often an adult female bird will flutter about in front of a snake in order to distract the snake from the fledglings in her nest. Another possible explanation may be that many animals are unable to perceive the slow approach of a long thin snake as dangerous. Finally, the fact that a snake is unable to blink may have something to do with the origin of this myth. Rat snake (Elaphe obsoleta)


Hoop Snakes
According to folklore, when frightened a hoop snake will bite its tail and form a rigid circle which allows it to travel downhill like a wagon wheel. Obviously, snakes are not anatomically equipped for rolling. There are no reliable accounts of this event ever taking place. The hoop snake myth may have originated from the observed behavior of mud snakes. Mud snakes in the southern United States will occasionally lie in a loose coil shaped like a loop, but when confronted they slither away from danger like other snakes.


Poisonous Breath
Some people believe that hognose snakes (Heterodon platirhinos; also called spreading adders or puff adders) are able to mix poison with their breath and kill a person at a distance of over twenty feet. In reality the breath of hognose snakes is harmless. Hognose snakes exhibit perhaps the most elaborate bluffing behavior of any snake. They may spread their hoods, hiss, and even strike, although they don't attempt to bite. If they are continually harassed, they will flip over on their back and play dead. Hognose snakes rarely bite people and their bite is usually less bothersome than a bee sting. Eastern Hognose Snake (Heterodon platirhinos)

Rattlesnakes Add One Rattle Every Year
It is often suggested that rattlesnakes add one rattle every year. Contrary to this belief, a rattlesnake adds one rattle every time it sheds its skin. Snakes may shed several times a year, each time adding a new rattle; in addition rattles may break off. For these reasons, counting rattles is not usually an accurate method of determining a rattlesnake's age.

Snakes Travel in Pairs
Another myth regarding snake behavior is that snakes travel in pairs, the survivor seeking revenge if one is killed. This myth is entirely false, snakes hardly ever travel in groups or pairs. Snakes do not have any social bonds and would feel in no way vengeful if one of its conspecifics were to be killed. One possible explanation for this myth may be that in a prime habitat situation, several snakes of the same species may be observed in a small area. Another possible explanation for the origin of this myth could be related to the typical reproductive behavior of snakes. During the mating season a male snake may closely follow a female snake much as a buck deer trails a doe during the rut.


Striking
Unfortunately some people are uninformed about the striking capabilities of snakes. Many people believe that snakes can only strike from a coiled position. In reality, snakes can bite or strike from any position. Coiling does however, increase the distance that a snake can strike. A common inquiry relating to cottonmouths (Agkistrodon piscivorous), concerns their ability to bite underwater. Cottonmouths can in fact bite underwater, which makes sense since they live in wetland habitats, and feed on fish and water snakes.

A related myth states that injured snakes die before sundown. This myth is of course false. A mortally wounded snake will usually die quickly, just like any other animal. Time of day has no bearing on the death of any animal. The origin of this myth may be related to the fact that nerve reflexes may cause muscle twitches for several hours after death, resulting in movements of the body and jaws. Because of the lingering nerve reflexes, even a dead venomous snake can be dangerous.

Sucking Milk
In farming communities throughout the world, it is a common superstition that snakes suck the milk from cows and goats. In North America, the milksnake (Lampropeltis triangulum) acquired its common name based on this myth. Although milksnakes may be common around barns, they lack the anatomical structures necessary to suck. A snake drinks by submerging its head, or at least its mouth, in water and it then takes in water by expanding its body wall. Milksnakes are common in barns because barns house an abundant supply of small rodents, their primary prey.

Swallowing Young
Many people believe that mother snakes will swallow their young when confronted with danger. Despite countless hours of observation, this behavior has never been documented. Swallowing young would not serve as a protective strategy in snakes because anything that enters the esophagus soon arrives in the stomach where it is promptly digested. Although thousands of dissections have been performed on female snakes, none have revealed a stomach full of baby snakes belonging to the same species.

‘Decline in snake population responsible for crop losses’

November 3rd, 2008 • Related • Filed Under
Filed Under: A-Zoo News
Tags: Agriculture Sector • Ecological Changes • Ecological Zones • Natural Enemies • Poisonous Species • Population Of Snakes • Reptiles And Amphibians • Snake Population • Species Of Snakes • Zoological Gardens

Monday, November 03, 2008
Karachi

The sharp decline in the population of snakes due to ecological changes is harming the agriculture sector, as the population of rats and other rodents is on the rise, said former director of Karachi Zoological Gardens Dr A. A. Quraishy.

According to Quraishy, growing deforestation was responsible for the decline in the population of snakes. The minimum requirement of an environment-friendly country was to have 25 per cent forest cover. This is in stark contrast to arid zones in Pakistan, where only 12.5 per cent forest cover existed.

Due to a very sharp decline in forestation and destruction of natural flora, the forest cover had reduced to 0.2 per cent all over Pakistan, and reflected desertification, claimed Dr Quraishy. Owing to the absence of natural cover, fauna-like mammals, birds, reptiles and amphibians have disappeared from Pakistan, he observed.

In this context, the decrease in snake population is harmful for the agricultural sector. Snakes are necessary for good agriculture produce as they eat natural enemies of crops, including rats and rodents, he said. Field rats are reported to consume about 25 per cent agriculture crop, while the presence of snakes in agricultural fields is necessary to reduce their population and to ensure the safety of crops, he added.

He said that in rural areas the destruction of crops due to increase in population of field rats was alarming. He said that 30 to 50 per cent of the crop yield was being destroyed by rodents.

Both poisonous and non-poisonous species of snakes that were once found in the country are now endangered in quality and quantity in deserts, arid zones, grassy landscapes, marshes, fresh water and other ecological zones of Pakistan, added Dr Quraishy.

He said that the present destruction and deforestation in lower Sindh and Balochistan had driven snakes out of their lairs, rocky abodes, grassy and bushy patches in the hinterland. Desperate and confused, these snakes run into the marshy outback, even entering dry patches, derelict huts and abodes left by the locals in hundreds of villages in lower Sindh and in the coastal belt of Balochistan, he said.

He added that the vicinity of villages suited them best as they provided them with their staple food - the field rats - that dug under the soft land of the cultivated fields, orchards, farms and nurseries.

Desert lizards, some twenty different species of small, medium and large size, also resided in these habitats, where they found shelter, food and breeding sites, said Dr Quraishy. The sandy dunes, banks of rivers and streams also helped them to escape from enemies, to digest their meal or to bring down their escalated body temperature in scalding summer, he added.

He said that the flood and showers wash away the wild grasses while stunted bushes and seasonal creepers help snakes and lizards to survive through changing seasons of the semi-desert. In Balochistan, there was a period when they could find cool strata in holes that they would dig, so as to survive the harsh summers and to hibernate in the winter. The same holds true for Sindh, where snakes lived in the vast expanse of desert.

The sharp decline in the population of the poisonous, non-poisonous snakes and lizards has increased the rate of breeding of at least twenty species that destroys around 30 to 50 percent of crop yield in fields, barns, storehouses and godowns, he said.

Dr Quraishy said that a healthy population of these reptiles in the past has kept rat population low. In the current situation, the heavy loss of food grains has also increased poverty and escalated the Gross National Product (GNP) gap on a national scale, he added.

The incessant capture of snakes and lizards for laboratories and the unchecked export of these species are mainly responsible for the sharp decline of these very environment and agricultural friendly fauna, he claimed.

He claimed that the laboratories have been using them for decades to milk and exploit the venomous snakes to manufacture sera against snakebites. After milking, they are not released in their original habitats, he claimed.

Dr Quraishy said that the death toll by snakebites had diminished just a whiff but the gross imbalance between the prey-predator levels had increased deaths by malnutrition in villages that were eating less food than their minimum nutrition requirement.

The increased rat population robs their crops at every level – in the seedpods, in barns and in homes where they spoil a great deal by their smelly droppings and urine, he said.

Dr Quraishy said that snake charmers were also starving as they did not find enough cobras and colourful non-poisonous snakes with which they used to amuse spectators, who in turn used to pay them for their love of labour, melodious gourd flute and antics.

Fla. fire-rescue puts antivenom bank to use

By Sallie James
The (Fort Lauderdale) Sun Sentinel

HOMESTEAD, Fla. — Members of Miami-Dade County's Venom Response Team call him a frequent flier because he has been bitten by venomous snakes so many times.

It happened again this past weekend, when longtime snake handler Albert Killian, 52, was cleaning out the cage of a deadly poisonous king cobra.

Killian was bitten by a snake that he once described as having "enough venom to drop an 8,000-pound elephant."

The animal curator at the nonprofit Everglades Outpost Inc. of Homestead was bitten in the left forearm shortly before 3 p.m. Sunday, according to Miami-Dade Capt. Ernie Jillson, who's in charge of the Venom Response Team.

Killian was taken to Homestead Hospital, where he had received more than 20 vials of anti-venin.

"It's an inherent risk that goes along with the job," Jillson said. "When you work with venomous snakes, it's not a matter of if, but when you will get bit. He wasn't doing anything wrong. He was doing what he normally does to take care of the snake."

Killian is "through the worst of it" and will likely be released in a few days, he said.

The bite from a king cobra can cause internal bleeding and respiratory failure, among other things.

"He was fortunate," Jillson said. "Without our anti-venin bank, he would not have survived."

Miami-Dade County Fire Rescue Department operates the only anti-venin bank of its kind in the United States, Jillson said. The agency has 43 antivenins for an array of reptile, insect and spider bites. It is currently the sole available public source in the U.S. for coral snake anti-venin.

In June, Killian spoke to the Sun Sentinel about the risks of handling venomous snakes and his love for the job. During the interview, he handled several snakes, including the king cobra that bit him Sunday, as well as a coral snake.

During the demonstration, Killian grasped the cobra with bare hands, then bent forward and kissed it on its head.

At another point, the snake swiped at Killian's bare leg.

"I've had my heart stop on me once, I've been in respiratory failure three times, and I've been in paralysis three times due to the bites of snakes," he said in June. "The worst thing about a neurotoxic bite is when you go into respiratory failure, and go into paralysis, your brain is completely awake. If someone lifts your eyelids, you can see them."

At the time of the interview, Killian told the Sun Sentinel his last venomous snake bite had occurred about four years earlier, when a Western diamondback rattlesnake struck him with a single fang during a demonstration for a group of students.

Killian, who began handling venomous snakes when he was in his 20s, considers every snake bite a learning experience. He acknowledged that the craft is risky, unpredictable business.

His left ring finger is permanently crooked from the tissue damage caused years ago by rattlesnake bite.

"Do it well when you do it, and don't do it often," Killian told the Sun Sentinel, chuckling.

World's Smallest Snake Discovered on Barbados

By Jeanna Bryner, Senior Writer

posted: 03 August 2008 08:00 am ET
As slim as a spaghetti noodle and able to fit snugly on a U.S. quarter, a new species of snake has been found hiding out in a forest on Barbados. The reptilian runt is now the world's smallest snake.

Blair Hedges, an evolutionary biologist at Penn State, discovered the snake, which just under four inches (10 cm) in length as an adult, in a fragment of forest on the eastern side of Barbados.

Hedges analyzed genetic material from the snake, which along with physical characteristics such as its unique color patterns and scales, provided evidence that the snake was indeed a new species of threadsnake, now dubbed Leptotyphlops carlae.

"Snakes may be prevented by natural selection from becoming too small because, below a certain size, there may be nothing for their young to eat," Hedges said.

The Barbados snake, like its relatives, likely feeds primarily on the larvae of ants and termites.

Like other members of the "small" club, L. carlae only produces one offspring at a time, in this case a single slender egg (some other snakes give birth to live young). In addition, its young are giants relatively speaking. In general, the hatchlings of the smallest snakes are one-half the length of an adult, while the largest snakes have hatchlings that are only one-tenth the length of an adult.

For instance, the hatchling of a king cobra, which can reach a length of 18 feet (5.5 meters), can be as long as about 14 inches (36 cm).

"If a tiny snake were to have two offspring, each egg could occupy only half the space that is devoted to reproduction within its body," Hedges said. "But then each of the two hatchlings would be half the normal size, perhaps too small to function as a snake or in the environment."

He added, "The fact that tiny snakes produce only one massive egg — relative to the size of the mother — suggests that natural selection is trying to keep the size of hatchlings above a critical limit in order to survive."

Hedges describes the new species in the Aug. 4 issue of the journal Zootaxa, where he also notes another new snake he discovered on the nearby island of St. Lucia. Also a type of threadsnake, the new species is just about as small as the Barbados one.

The finding doesn't surprise Hedges, who explains how unique organisms tend to be found on islands where species can evolve over time to fill the little nooks and crannies that are available as places to live, or to consume perhaps foodstuffs and other resources, unoccupied by other organisms.

The research was funded by NASA and the National Science Foundation.

How fangs developed in venomous snakes

July 31st, 2008 - 4:21 pm ICT by ANI

Washington, July 31 (ANI): New researcher from Leiden University in the Netherlands suggests that both rear and front fangs in venomous snakes developed from separate teeth-forming tissue at the rear of the mouth, unlike non-venomous snake dentition and human teeth.

Experts associate with this work say that it may help explain why snakes flourished beginning some 60 million years ago, geologically soon after non-avian dinosaurs went extinct.

“The snake venom system is one of the most advanced bioweapon systems in the natural world. There is not a comparable structure as advanced, as sophisticated, as for example a rattlesnake fang and venom gland,” Live Science quoted lead researcher Freek Vonk as telling Nature magazine.

Only the venomous snakes sport fangs sharp, enlarged teeth positioned along the upper jaw at the front or rear of a snake’’s mouth, and connected to venom glands.

The non-venomous snakes like pythons are equipped with only the normal rows of teeth.

The researchers say that even a venomous snake may sometimes impart a “dry” bite, not delivering the potent venom.

While most venomous snakes have fangs positioned in the rear of the mouth, some like rattlesnakes, cobras and vipers, have fangs jutting down from their upper jaws in the front of the mouth.

“If you want to eat a very dangerous prey, like a big rat with razor-sharp rat teeth, then it would be more advantageous to have your fangs in front of the mouth so you can just bite it quickly and then let go, instead of biting it and holding on and then chewing the venom into the tissue, because then the rat can bite back,” Vonk said.

With a view to determining how both types of snake fangs evolved from non-fanged species, the researchers looked at fang development in 96 embryos from eight living snake species.

Vonk says that the analyses conducted by him and his colleagues showed that the front and rear fangs develop from a separate teeth-forming tissue at the back of the upper jaw.

For all front-fanged venomous snake species, the front fangs displaced forward during embryo development by rapid growth of the embryonic upper jaws.

The rear fangs stayed put where they formed, said the researchers.

The uncoupled rear part of the teeth-forming tissue evolved in close association with the venom gland, thereafter forming the fang-gland complex. The uncoupling allowed this to happen, because the rear part of the teeth-forming tissue did not have constraints anymore from the front part,” Vonk said.

He said that the separate development of the rear part of the tissue might have played a major role in snakes” ability to diverge into the 3,000 species found throughout the world at present.

“It sheds light on one of those nagging questions in herpetology how did a diversity of fang types among snakes evolve?” said David Kizirian, a herpetologist at the American Museum of Natural History in New York who was not involved in the study. (ANI)

West Bengal’s snake charmers close to starvation

February 18th, 2008 - 1:10 pm ICT by admin

Kolkata, Feb 18 (ANI): Snake charmers in Kolkata and other parts of West Bengal have said that they are on the verge of starvation following a government order to ban the keeping of snakes.
“From the time of my father, grandfather, we have been in the snake charming profession. The law has banned this tradition but we continue with the trade to make a living,” claimed Lalu Sapuria, a snake charmer.
The Government banned the keeping of snakes as pets under the Wildlife Protection Act, 1972. The Act also prohibits snake charmers from catching snakes or using them for entertainment.
Voluntary groups, however, say snake charmers are a part of the country’s heritage and insist that their traditional knowledge should be preserved and developed as a modern science.
“In India, some 800,000 people are associated with the tradition of snake charming. In West Bengal, there are 100,000 snake charmers. The snake charmers are backward. They have no voter identification cards or ration cards. We have tried to bring them under one organization to help them,” said Raktim Das, an organiser of the Snake Charmers’ Federation of India.
Snake charmers are demanding the right to catch snakes and to sell venom of theses reptiles to snakebite antidote manufacturers.
According to the World Wildlife Fund survey on the occasion of Nagpanchmi, some 70,000 snakes die of pneumonia, lung infection, sepsis and milk allergy. (ANI)

UPDATED INFO ON KING COBRA'S ANTI-VENOM PRODUCTION

OPHIOPHAGUS HANNAH
Synonyms: Hamadryad, Jungle Cobra, King Cobra
Classification: Snake (animal group), Elapidae (family), OPHIOPHAGUS (genus)
Indicated antivenom:
Antivenom Type of antibody Number of holding centres
1. KING COBRA ANTIVENIN® Thai Red Cross, Thailand
specific 45
5
2. MONOVALENT COBRA VENOM ANTISERUM® Central Research Institute, India
paraspecific 67
0
3. POLYVALENT ANTI SNAKE VENOM SERUM® Central Research Institute, India
paraspecific 71
0
Countries of holding centres: GERMANY, SWEDEN, SWITZERLAND
MAVIN: Version February 01, 2007
CountryCityHolding centre and its antivenomsGERMANY81675 Muenchen
Ismaningerstr. 22
Giftnotruf Muenchen, Klinikum Rechts der Isar
Tel:+49-89-19240; Fax:+49-89-41402467; Email:tox@Lrz.tum.de.
1. KING COBRA ANTIVENIN® Thai Red Cross, Thailand
No. of vials: 3. Expiration date: September.2006. Last update: 16.01.2007
SWEDEN11181 Stockholm
Klarabergsgatan 64, Box 1157
Apoteket C.W. Scheele, Emergency-pharmacy Stockholm
Fax:+46-8-7918877.
1. KING COBRA ANTIVENIN® Thai Red Cross, Thailand
No. of vials: 20. Expiration date: November.2006. Last update: 12.01.2007
No. of vials: 20. Expiration date: October.2009. Last update: 12.01.2007
SWITZERLAND1077 Servion
For this holding centre please contact: Giftnotruf Muenchen, Klinikum Rechts der Isar
Tel:+49-89-19240; Fax:+49-89-41402467; Email:tox@Lrz.tum.de.
1. KING COBRA ANTIVENIN® Thai Red Cross, Thailand
No. of vials: 15. Expiration date: December.2006. Last update: 15.01.2007
SWITZERLAND1211 Geneve 4
For this holding centre please contact: Giftnotruf Muenchen, Klinikum Rechts der Isar
Tel:+49-89-19240; Fax:+49-89-41402467; Email:tox@Lrz.tum.de.
1. KING COBRA ANTIVENIN® Thai Red Cross, Thailand
No. of vials: 5. Expiration date: October.2009. Last update: 12.01.2007
SWITZERLAND8596 Münsterlingen
Postfach
Institut für Spitalpharmazie, Kantonsspital Münsterlingen
Tel:+41-71-6862244(during business hours), 6861111(emergency); Fax:+41-71-6862239.
1. KING COBRA ANTIVENIN® Thai Red Cross, Thailand
No. of vials: 5. Expiration date: September.2006. Last update: 12.01.2007

Ophitoxaemia (Venomous snakebite)

Joseph L. Mathew
Tarun Gera

Address for correspondence:
Dr. Tarun Gera
B - 256, Derawala Nagar,
Delhi-110009,
India
E-mail : jlm@rediffmail.com, tarun256@hotmail.com

* Introduction
* Epidemiology
* Systemic Manifestations
* Local Manifestations
* Unusual and Rare Manifestations



* Factors influencing outcome
* Laboratory features
* Management
* First Aid
* Specific Therapy



* Supportive Therapy
* Mortality
* Conclusion
* References

INTRODUCTION

Ophitoxaemia is the rather exotic term that characterizes the clinical spectrum of snake bite envenomation. Of the 2500-3000 species of snakes distributed world-wide, about 500 are venomous. Based on their morphological characteristics including arrangement of scales, dentition, osteology, myology, sensory organs etc., snakes are categorized into families. The families of venomous snakes are Atractaspididae, Elapidae, Hydrophidae and Viperidae.
The major families in the Indian subcontinent are: Elapidae which includes common cobra, king cobra and krait, Viperidae which includes Russell's viper, pit viper and saw-scaled viper and Hydrophidae (the sea snakes) [1]. Of the 52 poisonous species in India, majority of bites and consequent mortality is attributable to 5 species viz. Ophiophagus hannah (king cobra), Naja Naja (common cobra), Daboia rusellii (Russell's viper), Bungarus caeruleus (krait) and Echis carinatae (saw-scaled viper). There are 14 venomous species in Nepal. These include pit vipers (5 species), Russell's viper, kraits (3 species), coral snake and 3 species of cobra including the king cobra [2].

EPIDEMIOLOGY OF SNAKE BITE

Snake bite remains a public health problem in many countries even though it is difficult to be precise about the actual number of cases. It is estimated that the true incidence of snake envenomation could exceed 5 million per year. About 100,000 of these develop severe sequelae. The global disparity in the epidemiological data reflects variations in health reporting accuracy as well as the diversity of economic and ecological conditions [3].

To complicate matters further, accurate records to determine the exact epidemiology or even mortality in snake bite cases are also generally unavailable [1]. Hospital records fall far short of the actual number owing to dependence on traditional healers and practitioners of witchcraft etc. It has been reported that in most developing countries, upto 80% of individuals bitten by snakes first consult traditional practitioners before visiting a medical centre [4,5]. Owing to the delay several victims die during transit to the hospital. Nevertheless, Swaroop reported about 200,000 bites and 15,000 deaths in India due to snake bite poisoning as far back as 1954 [6]. Based on an epidemiological survey of 26 villages with a total population of nearly 19,000 individuals in Burdwan district of West Bengal state in India, Hati et al worked out an annual incidence of 0.16% and mortality rate of 0.016% per year [7]. In Sri Lanka, the overall annual mortality from a single venomous species ranges from 5.6 per 100,000 to as high as 18 per 100,000 in some areas [8]. Myanmar seems to have the highest mortality in Asia and 70% snakebites are by Russell's viper [9.10]. However, this may only reflect a better reporting system prevalent in that country. Maharashtra, one of the states of India with the highest incidence, reported 70 bites per 100,000 population and mortality of 2.4 per 100,000 per year [11]. The other states with a large number of snakebite cases include West Bengal, Tamil Nadu, Uttar Pradesh and Kerala [1].
It has been estimated that 150 to 200 ophitoxaemia related deaths occur annually in Nepalese hospitals [12]. The WHO estimated over 20,000 cases and 1000 deaths from ophitoxaemia in Nepal [13].

Chippaux has stressed the importance of distinguishing between hazardous snakebites, which occur when humans encounter a snake accidentally and 'illegitimate' snakebites inflicted by an animal kept in captivity, or during snake handling. In industrialized countries the frequency of illegitimate snake bites is increasing while hazardous bites predominate in developing countries [3].

The age and sex incidence of snake bite victims throws light on the vulnerable section of the population. While snake bite is observed in all age groups, the large majority (90%) are in males aged 11-50 years. The predominance of male victims suggests a special risk of outdoor activity [14].

The high incidence of snake bite between 0400 hours to midnight corresponds well with the period of maximum outdoor activity observed in most studies. The incidence of snake bite shows a distinct seasonal pattern closely related to rainfall and temperature which compels the reptiles to come out of their shelter [14].

Most patients are unable to identify the snake species either because of ignorance or poor visibility in darkness. A large number of bites occur in fields, most individuals are unable to spot the snake due to tall grass and crops. The observation that the most frequent site of bite is the lower extremity suggests that in most cases the snake is inadvertently trodden upon.
Among the host factors, people involved in occupations and/or lifestyles requiring movement in dense undergrowth or undeveloped land, are the worst affected. These include farmers, herders and hunters [15] and workers on development sites. Paul reported an incidence of 7-15 percent in children less than10 years [16]. Another study reported 37% incidence in the second decade of life [14]. The sex ratio seems almost uniform all over with males being affected twice or thrice as commonly as females [16]. For obvious reasons, bites are maximal in lower limbs (about two thirds) [17] with 40 percent occurring in feet alone.

Morbidity and mortality resulting from snake-bite envenomation also depends on the species of snake involved, since the estimated "fatal dose" of venom varies with species. In the Indian setting, almost two-thirds of bites are attributed to saw-scaled viper (as high as 95% in some areas like Jammu) [18], about one fourth to Russell's viper and smaller proportions to cobra and kraits [19]. In Sri Lanka, Daboia russellii accounts for 40% of bites and Naja naja for another 35% [8,20]. Daboia russellii alone accounts for 70% bites in Myanmar [9,10]. Among the various species, the average yield per bite in terms of dry weight of lyophilised venom is 60 mg for cobras, 63 mg for Russel's viper, 20 mg for krait and 13 mg for saw scaled viper. The respective "fatal doses" are much smaller viz 12 mg, 15 mg, 6 mg and 8 mg [21]. However, clinical features and outcomes are not as simple to predict because every bite does not result in complete envenomation [22]. Epidemics of snake bite following floods owing to human and snake populations getting concentrated together have been noted in Pakistan, India and Bangladesh.

PATHOPHYSIOLOGY OF OPHITOXAEMIA

Snake venom, the most complex of all poisons is a mixture of enzymatic and non-enzymatic compounds as well as other non-toxic proteins including carbohydrates and metals. There are over 20 different enzymes including phospholipases A2, B, C, D hydrolases, phosphatases (acid as well as alkaline), proteases, esterases, acetylcholinesterase, transaminase, hyaluronidase, phosphodiesterase, nucleotidase and ATPase and nucleosidases (DNA & RNA) [1]. The non-enzymatic components are loosely categorized as neurotoxins and haemorrhagens [16]. Different species have differing proportions of most if not all of the above mixtures- this is why poisonous species were formerly classified exclusively as neurotoxic, haemotoxic or myotoxic. The pathophysiologic basis for morbidity and mortality is the disruption of normal cellular functions by these enzymes and toxins. Some enzymes such as hyaluronidase disseminate venom by breaking down tissue barriers. The variation of venom composition from species to species explains the clinical diversity of ophitoxaemia. There is also considerable variation in the relative proportions of different venom constituents within a single species throughout its geographical distribution, at different seasons of the year and as a result of ageing.
The various venom constituents have different modes of action. Ophitoxaemia leads to increase in the capillary permeability which may cause loss of blood and plasma volume into the extravascular space. This accumulation of fluid in the interstitial space is responsible for edema. The decrease in the intravascular volume may be severe enough to compromise circulation and lead on to shock. Snake venom also has direct cytolytic action causing local necrosis and secondary infection, a common cause of death in snake bite patients. The venom may also have direct neurotoxic action leading to paralysis and respiratory arrest, cardiotoxic effect causing cardiac arrest, myotoxic and nephrotoxic effect. Ophitoxaemia also causes alteration in the coagulation activity leading to bleeding which may be severe enough to kill the victim.

CLINICAL MANIFESTATIONS

The clinical manifestations of snake-bite occur in a wide spectrum with some bites resulting in minimal or no symptoms at all, while others are severe enough to result in systemic manifestations and even death. Besides discussing these, we have also tried to include unusual and rare presentations of ophitoxaemia.

SNAKE BITES WITH NO MANIFESTATIONS

The most obvious explanation for a confirmed snake-bite but no clinical manifestations is bite by a non-poisonous species. However, it is well documented that a large number of poisonous species also often do not cause symptoms. In a study of 432 snake-bites in North India, Banerjee noted that 80% of victims showed no evidence of envenomation [1]. This figure correlates almost exactly with a more recent observation from Brazil [24]. Reid also states that over 50% of individuals bitten by potentially lethal venomous snakes escape with hardly any features of poisoning [22]. This is corroborated by Saini's study of 200 cases in Jammu region in India, in which only 117 showed symptom/sign of envenomation [19]. From the relatively low frequency of poisoning following snakebites, it has been suggested that snakes on the defensive when biting humans seldom inject much venom [25]. Other possible explanations include a bite without release of venom (dry bite). In a study of 40 bites by snakes which were captured and identified as poisonous, about one- third showed no clinical or laboratory evidence of systemic envenoming suggesting a high incidence of dry bites [26]. There are also cases wherein venom is spewed into the victim's body as the snake attempts to bite, thereby reducing the overall quantity of venom in the blood stream. Lamb has recorded that almost 30% of cobra bites are "superficial" with minimal envenomation. Other protective factors include the layers of clothing or boot leather through which the snake sometimes strikes [27].

LOCAL MANIFESTATIONS

With the possible exception of the psychological trauma of being bitten, local changes are the earliest manifestations of snake bites [28]. Features are noted within 6-8 minutes but may have onset up to 30 minutes [21,29]. Local pain with radiation and tenderness and the development of a small reddish wheal are the first to occur. This is followed by oedema [16], swelling and appearance of bullae - all of which can progress quite rapidly and extensively even involving the trunk [19]. Tingling and numbness over the tongue, mouth and scalp and paraesthesias around the wound occur mostly in viper bites [21]. Local bleeding including petechial and/or purpuric rash is also seen most commonly with this family. Regional lymphadenopathy has been reported as an early and reliable sign of systemic poisoning [30]. The local area of bite may become devascularized with features of necrosis predisposing to onset of gangrenous changes. Generally Elapid bites result in early gangrene-usually-wet type whereas vipers cause dry gangrene of slower onset; though one of the authors (JLM) has also seen the reverse pattern. There are two interesting case reports of Raynaud's phenomenon and gangrene in a limb different from the one bitten - both bites were by Russell's viper [31]. Secondary infection including tetanus and gas gangrene may also result [1].

SYSTEMIC MANIFESTATIONS

As mentioned previously, the most common and earliest symptom following snake bite (poisonous or non poisonous) is fright [28], particularly of rapid and unpleasant death [21]. Owing to fright, a victim attempts 'flight' which unfortunately results in enhanced systemic absorption of venom. These emotional manifestations develop extremely rapidly (almost instantaneous) and may produce psychological shock and even death. Fear may cause also transient pallor, sweating and vomiting. The time onset of poisoning is similar in different species. Cobra produces symptoms as early as 5 minutes [16] or as late as 10 hours [28] after the bite. Vipers take slightly longer - the mean duration of onset being 20 minutes [16]. However, symptoms may be delayed for several hours. Sea snake bites almost always produce myotoxic features within 2 hours so that they are reliably excluded if no symptoms are evident within this period [16].

Other systemic manifestations depend upon the pathophysiological changes induced by the venom of that particular species (See Fig. 1). As mentioned previously, based on the predominant constituents of venom of a particular species, snakes were loosely classified as neurotoxic (notably cobras and kraits), hemorrhagic (vipers) [2] and myotoxic (sea snakes). However it is now well recognized that such a strict categorization is not valid as each species can result in any kind of manifestations. Neurotoxic features are a result of selective d-tubocurarine like neuro-muscular blockade which results in flaccid paralysis of muscles [16]. Cobra venom is however 15-40 times more potent than tubocurarine [1]. Ptosis is the earliest [1] neuroparalytic manifestation followed closely by opthalmoplegia. Paralysis then progresses to involve muscles of palate, jaw, tongue, larynx, neck and muscles of deglutition-but not strictly in that order [16]. Generally muscles innervated by cranial nerves are involved earlier [1]. However, pupils are reactive to light till terminal stages [1]. Muscles of chest are involved relatively late with diaphragm being the most resistant. This accounts for the respiratory paralysis, which is often terminal. Reflex activity is generally not affected in ophitoxaemia and deep tendon jerks are preserved till late stages [1]. Onset of coma is variable, however several cases of cobra bite progress to coma within 2 hours of bite. Symptoms that portend paralysis include repeated vomiting, blurred vision, paraesthesiae around the mouth, hyperacusis, headache, dizziness, vertigo and signs of autonomic hyperactivity.

Cardiotoxic features include tachycardia, hypotension and ECG changes. Cardiotoxicity occurs in about 25% viperine bites and includes rate, rhythm and blood pressure fluctuations [32]. In addition, sudden cardiac standstill may also occur owing to hyperkalemic arrest. Non dyselectrolytemic acute myocardial infarction has also been reported [33]. Tetanic contraction of heart following a large dose of cobra venom has been documented in vivo and in vitro [34]. There is a single case report of non-bacterial thrombotic endocarditis following viper bite [35]. Myalgic features are the most common presentation of bites by sea snakes. Muscle necrosis may also result in myoglobinuria.

Snake venoms cause haemostatic defects by a number of different mechanisms. Some cause activation of intravascular coagulation and result in consumption coagulopathy. Notable in this group is Daboia russelli which has procoagulant activating factors V and X. Certain other venoms cause defibrinogenation by activating endogenous fibrinolytic system [35,36]. Besides direct effects on the coagulation cascade, venoms also can cause qualitative and quantitative defects in platelet function [39]. In India and Sri Lanka, Russell's viper envenomation is often associated with massive intravascular haemolysis [37]. Haematological changes - both local as well as systemic - are some of the commonest features of snake bite poisoning. Bleeding may occur from multiple sites including gums [17], GIT (haematemesis and melaena), urinary tract, injection sites and even as multiple petechiae and purpurae [28]. Subarachnoid haemorrhages were documented in 5 of 200 cases in Saini's series of patients in Jammu region [19]. In addition cerebral haemorrhage [39] and extradural haematoma [40] have also been reported. Almost every species of snake can cause renal failure. It is fairly common following Russell's viper bite and is a major cause of death [41] In a series of 40 viper bites, renal failure was documented in about a third [42]. The extent of renal abnormality in them correlated well with the degree of coagulation defect; however in a majority renal defects persisted for several days after the coagulation abnormalities normalised: suggesting that multiple factors are involved in venom induced ARF.

Rarer systemic manifestations including hypopituitarism [43,44], bilateral thalamic haematoma [45] and hysterical paralysis [46] have also been reported.

MORTALITY

While there are many factors influencing the outcome in victims of snake-bite, there is an overall agreement in the case fatality rate - generally varying from 2-10%[16,47-51]. The mortality rate is higher in children owing to larger amount of toxin per kg body weight absorbed [27]. There is significantly higher mortality among victims who develop neurotoxicity [47,51]. On an average - cobras and sea snakes result in about 10% mortality [28]-ranging from 5-15 hours following bite. Vipers have a more variable mortality rate of 1-15% and generally more delayed (up to 48 hours) [22].

UNUSUAL AND RARE MANIFESTATIONS OF OPHITOXAEMIA
Delayed manifestations

Authors are all uniform in their opinion that delayed onset of signs is rare. In their series of 56 cases, Saini et al documented 4 patients who had normal clinical and laboratory coagulation profile at admission shortly following bite, but started bleeding as late as 4-6 days after the bite [9]. Reid has noted that haemorrhage in the brain may be delayed up to one week after bite [28]. The possible explanation for these manifestations is that local blebs constitute a venom depot which is suddenly released into the blood stream, especially when the wound is handled surgically [29]. Further, these depots are generally inaccessible to antivenom. Nevertheless we have experience of a case showed good response to antivenom injected twice (24 hour and 36 hour after bite) and still developed features of systemic neurotoxicity on the 7th day, despite remaining well for 51/2 days (unpublished observation). This occurred without any interference at the local site. There is also the interesting report of a zookeeper bitten on the finger following which he was administered antivenom. This prevented the development of systemic poisoning but had no effect on the extent of local complications. This individual developed compartment syndrome and spontaneous rupture of the extensor tendon of the involved finger several weeks after the bite suggesting a delayed manifestation even in the absence of systemic poisoning [52]. Kumar et al have reported a singular occurrence of unconsciousness 6 days after an individual was bitten- he remained symptom free for the first 5 days [53].
Recurrent manifestations
Recurrence of manifestations has not been discussed in most of the published literature. The only record is Warrell's assertion that signs of systemic envenomation may recur hours or even days after initially good response to antivenom. This has been explained by ongoing absorption of venom from the blood - which has a half life of 26-95 hours [17]. He therefore suggests daily evaluation of patients for at least 3-4 days. This theory would probably not be able to account for our experience of recurrence of neurotoxic manifestations in a 10 year old child bitten by a cobra, that occurred 12 hours after a relatively large dose of antivenom (10 vials). This child responded well to an additional dose of 10 more vials (Unpublished observations). Available literature suggests the use of antivenom till symptoms and signs are controlled, with some authors recommending its use as and when necessary [17]. Nevertheless, recurrence of signs of envenomation is still a rarity.

Long term effects of snake bite [22]

In most cases, swelling and oedema resolve within 2 to 3 weeks. However, they may occasionally persist up to 3 months. In exceptional circumstances, they may also be permanent. There are records, which suggest that coagulation disturbances [28] and neurotoxicity may persist beyond 3 weeks. Necrosis of the local tissue, resultant gangrene and the consequent cosmetic defects are obvious long term effects of ophitoxaemia [28].

Manifestations of snake bite not because of toxemia

Cases have been reported wherein the clinical manifestations of snake bite are not because of the poisoning, but due to venom hypersensitivity [27]. This has been noted, irrespective of a history of previous bite by the same or different species. Such patients may manifest with anxiety, cutaneous sensitivity or tightness in the throat. They may also present with features of anaphylactic shock. In a study of victims of Bothrops bite in rural Argentina, it was noted that individuals bitten twice developed hives and angioedema within 15 minutes of the second bite. Specific antibodies - both IgE and IgG were detectable in their serum . The crossreactivity among the venom of Bothrops sp suggests that these signs are because of specific IgE antibodies against venom and must not be interpreted with toxic effects that appear late [55].

Toxemia without bite

Naja nigricollis (spitting cobra) is a species which can eject venom with considerable accuracy even from a distance of 6-12 feet [17]. The exact range and target of this snake's venom is a matter of considerable debate among herpetologists. Most are in agreement that the venom is aimed at the victim's eyes resulting in conjunctivitis and corneal ulceration. The latter may be deep enough to cause anterior uveitis and hypopyon [56]. There are patients who have required enucleation of both eyes following a vicious attack by the spitting cobra. Besides the local manifestation, a dull headache persisting beyond 72 hours is a common feature. Spitting cobra is an exotic species since even the king cobra does not eject venom in this manner.

Bite by a killed snake
There are instances on record wherein a recently killed snake and even those with severed heads have ejected venom into those handling them. This is the basis for the absolute ban on handling and extreme caution in transportation which is usually advocated for killed snakes [17].

FACTORS AFFECTING SEVERITY AND OUTCOME IN OPHITOXAEMIA

There are several agent, host and environmental factors that modify the clinical presentation and resultant mortality of ophitoxaemia.

Children overall fare worse than adults owing to greater amount of toxin injected per unit body mass [16]. For the same age, individuals in a better state of health fare better than more debilitated counterparts [27]. Patients bitten on the trunk, face and directly into bloodstream have a worse prognosis [16]. Reid however asserts that the age of the victim and part of body bitten have no relation to outcome [29]. Exercise and exertion following bite results in enhanced systemic absorption of venom. This is why individuals who panic and flee from the scene of bite generally have a worse outcome [57]. The protection afforded by layers of clothing or shoes sometimes mitigates the effects of envenomation to a considerable extent [27]. Sensitivity of individual to venom naturally modifies the clinical picture as explained earlier [27]. Victims of ophitoxaemia who develop secondary infection at the site of bite fare worse than those uninfected [57].

The number and depth of the bites inflicted by the snake is a relative index of the amount of venom injected [16]. Indirect evidence for this is also available by studying the volume of venom remaining in the glands and fangs. The condition of fangs, intact or broken, is also an indirect indicator of amount of envenomation. The species of snake which has bitten alters outcome since the amount of venom injected and the 'lethal dose' varies with species [21]. The length of time a snake clings to its victim and the presence or absence of pathogenic organisms in its mouth are two other agent factors affecting outcome. The time of bite (day or night) and breeding habits of the snake are not related to outcome in any way [27]. The size of snake does not appear to be related to the efficacy of envenomation since several small specimens also have lethal capacity.

Among the environmental factors, the nature of first-aid and the time elapsed before administration is perhaps the single most important factor affecting outcome [27]. The circumstances that provoked the snake to bite may also have a bearing on clinical presentation and survival of victims.

APPROACH TO AN INDIVIDUAL ' ALLEGEDLY BITTEN' BY A SNAKE

This section is included here because of the importance of confirming an alleged bite by a snake. This has relevance on the management issues. Quite often, the victim who has ventured into open fields or dense undergrowth is bitten by a species which is not immediately identifiable. In addition, the psychological reaction generated by this unexpected event impels him/her to flee: thereby further reducing the probability of confirming the snake-bite. Therefore, in a patient presenting with history suggestive of snake-bite, it is important to address the following questions .



1. Is it actually a snake bite?

The classical setting for a snake bite has been described above. Bite is identified by the presence of 2 puncture wounds which may vary in distance from a few millimeters to as much as 4 cms, depending on the species. The depth of the bite varies anywhere from 1-8 millimeter [2]. In some cases, fang puncture sites are not easily visible. They may be brought to view by Bailey's method of injecting lignocaine through a fine gauge needle and observing the sites where it oozes from [27]. In some cases of bite, fang marks may not be visible at all. This has been attributed to a glancing strike or protection by clothing or foot wear. For the same reason, puncture wounds may even be single at times. There are instances wherein a snake has attacked repeatedly leaving multiple puncture marks [27]. Non-poisonous snakes generally leave a row of tooth impressions, but not fangs marks [21]. However, it is advocated that too much stress should not be laid on this rather variable feature.

2. Could it be anything else?

Russell contends that the marks left by snakes may be so variable as to make it difficult to distinguish from bites of rats, mice, cats and even lizards. They may also be confused with insect and scorpion bites/stings. Scratches or penetration by thorns or cactus may also leave marks like those of fangs; all these may be accompanied by local changes further compounding the problem of correct diagnosis [27].



3. Is it likely to be a poisonous species?

There is no simple, reliable method to distinguish poisonous from non-poisonous species. Poisonous species generally have fangs but these may be very small in elapids and not easily visible in vipers. Tails are usually not compressed and belly scales are small in non-venomous species - all of which are opposite in poisonous species [21]. Short of identifying the offending reptile, the only way to determine the poisonous nature of a species is to watch for features of envenomation viz local changes and/or systemic features.



4. Which species is involved?

Among the commonest poisonous species in India, the cobra (nag) is easiest to identify owing to a mental picture well entrenched in most peoples minds. Technically, however it is described as having a hood bearing a single or double spectacle shaped mark on its dorsal aspect. A white band in the region where the body touches the hood is another identifying feature. The common krait (karayat) is steel blue, often shining and has a single or double white band across the back. The head is covered with large shields. In general, elapidae have relatively short, fixed front fangs; as do the Hydrophidae. Russell's viper (daboia, kander) is identified by its flat, triangular head with a white 'V' shaped mark and three rows of diamond-shaped black or brown spots along the back. The sawscaled viper (afai) is distinguished from the other species by a white mark on the head resembling a bird's footprint or an arrow. The fangs of vipers are long, curved, hinged, front fangs, which have a closed venom channel, giving them a structure akin to a hypodermic needle. Besides these, there are several other differentiating characteristics among the poisonous snakes, which are of more interest to an expert than medical personnel. It has been claimed that most venomous species produce characteristic sounds, which may help in identification. These include hissing (Russell's viper), rasping (saw-scaled viper) and 'growling' (king cobras).

LABORATORY AIDS IN OPHITOXAEMIA

The laboratory serves rather poorly in the diagnosis of snake-bite, with the exception of ELISA studies which are now available to identify the species involved, based on antigens in the venom [22]. These tests are expensive and not freely available-hence of limited value; except for epidemiological study [16]. Laboratory tests are useful for monitoring, prognosticating victims of ophitoxaemia, as well as determining stages of intervention. Recently emphasis is being laid on the value of immuno-enzymatic tests to identify the offending species accurately [58].
Blood changes include anaemia, leucocytosis and thrombocytopenia [16]. In addition, peripheral smear may show evidence of haemolysis, particularly in viperine bites [19]. Deranged coagulant activity manifested by prolonged clotting time and prothrombin time may also be evident [28]. The quality of clot formed may be a better indicator of coagulation capability than the actual time required for formation, since clot lysis has been observed in several patients who had normal clotting time [19]. Hypofibrinogenemia may also be evident [16]. Among the metabolic changes, hyperkalaemia and hypoxemia with respiratory acidosis, especially with neuroparalysis may be present [16].
Urine examination could reveal haematuria, proteinuria, haemoglobinuria or myoglobinuria. In cases of ARF, all features of azotemia are also present. CSF haemorrhage has been documented in a minority of victims [16,19].

ECG changes are generally non-specific and include alterations in rhythm (predominantly bradycardia) and atrioventricular block with ST segment elevation or depression. T wave inversion and QT prolongation [1] have also been noted. Tall T waves in lead V2 and patterns suggestive of acute anterior wall infarction have been reported as well [32]. In addition, cases who develop hyperkalaemia manifest typical changes of this dyselectrolytaemia [17].
Serum cholesterol at admission has been found to correlate negatively with severity of envenomation. Rabbits exposed to snake venom in an experimental setting were noted to have a dose dependent decrease in serum cholesterol. This fall which is independent of the fall in serum albumin can only partially be explained by transcapillary lipoprotein leakage. It is more likely an indication of change in lipoprotein transport and metabolism as a result of phospholipase A2 in venom [59].

Recently EEG changes have been noted in up to 96% of patients bitten by snakes; starting within hours of the bite. Interestingly none of them showed any clinical features suggestive of encephalopathy. 62% showed grade I changes defined as decrease in (activity or/and increase in -activity or presence of sharp waves. 31% cases manifested grade II changes viz. sharp waves or spikes and slow waves; classified as moderate to severe abnormality. The remaining 4% showed severe abnormality with diffuse (activity (grade III). These abnormal EEG patterns were picked up mainly in the temporal lobes [60].

MANAGEMENT OF OPHITOXAEMIA

A review of literature pertaining to management of snake bite makes interesting reading, particularly with respect to traditional methods [27]. However, even a brief review of these novel practices is beyond the scope of the present discussion. Management aspects are fraught with controversy with experts differing over most, if not all facets of therapy. Owing to the variables involved in therapy, an ideal prospective clinical trial will likely never be done [61]. This article attempts to discuss management under the following heads:

a) First aid
b) Specific therapy
c) Supportive therapy

First aid

Most physicians are in disagreement with regard to nature, duration and even necessity of first aid. Russell advises minimal wastage of time with first-aid measures which often end up doing more harm than good [27]. Nevertheless, it is felt that reassurance and immobilization of the affected limb with prompt transfer to a medical facility are the cornerstones of first-aid care [16,22]. Most experts also advocate the application of a wide tourniquet or crepe bandage over the limb to retard the absorption and spread of venom [16,28]. The tourniquet should be tight enough to occlude the lymphatics, but not venous drainage [1]; though some also prefer to occlude the veins. Enough space to allow one finger between the limb and bandage is most appropriate. Should the limb become edematous, the tourniquet should be advanced proximally [16]. Tourniquets should never be left in place too long for fear of distal avascular necrosis [27]. In a recent report from Brazil, two cases were reported to have increased local envenoming subsequent to a tourniquet [62].

It was formerly believed and therefore advocated that incision over the bite drains out venom. However, it has now been established from animal experiments that systemic venom absorption starts almost instantly; this form of 'therapy' is therefore being questioned [27,28]. Some experts suggest that longitudinal incisions within fifteen minutes of the bite may be beneficial [1].
Suction of the local area, a staple of snake-bite management in Indian cinema, also has its advocates and detractors. While most have rejected it for its questionable efficacy [63], there are others who advise this method on the grounds of rapidly removing a large amount of venom [64]. There is a patented device, the Sawyer extractor available in the United Kingdom for this purpose [64]. It's suggested use has generated controversy with a series of letters to the editor of NEJM justifying or condemning its use [64,65].

Reid has advised that the wound site be minimally handled. Most authors recommend saline cleaning and sterile dressing [28]. Some however advise that the wound be left open [1,29].
There is disagreement over the use of drugs as part of first-aid care. It has been suggested that NSAIDS particularly aspirin may be beneficial to relieve local pain. Russell however dissuades use of analgesic and in particular aspirin for fear of precipitating bleeding [27]. In Reid's experience, pain relief with placebo was as effective as NSAID [22]. Codeine may be useful in some cases [1]. Similarly there are proponents as well as opponents for use of sedatives [27].
Almost all experts agree that the offending snake must not be provoked further by attempts to capture or kill it [27]. This is for fear of provoking an already enraged reptile to strike again. However, Gellert insists that in the United States, carnivorous bats and animals which bite man are captured as per guidelines of CDC to examine for rabies; therefore a snake should be treated no differently and every effort should be made to capture/kill it [65].

Specific therapy - Antivenom

Antivenoms are prepared by immunizing horses with venom from poisonous snakes and extracting the serum and purifying it. Antivenoms or antivenins may be species specific (monovalent) or effective against several species (polyvalent). Monovalent antivenom is ideal [1], but the cost and non-availability, besides the difficulty of accurately identifying the offending species - makes its use less common [17].

Indications for use

There are specific indications for use of antivenom [11,17]. Every bite, even if by poisonous species does not merit its use. This caution against the empirical use of antivenom is due to the risk of hypersensitivity reactions [28,29]. Therefore, antivenom is indicated only if serious manifestations of envenomation are evident viz coma, neurotoxicity, hypotension, shock, bleeding, DIC, acute renal failure, rhabdomyolysis and ECG changes [16]. In the absence of these systemic manifestations, swelling involving more than half the affected limb [1], extensive bruising or blistering and progression of the local lesions within 30-60 minutes [1] are other indications.
In a study of Elapid ophitoxaemia from India, victims with neuromuscular paralysis were administered anticholinesterase/neostigmine. Four of the patients did not receive any antivenom; all survived. Of 8 who received antivenom 3 were given less than 50 units; all 3 survived. The other 5 were administered more than 50 units; however 2 died. The authors concluded that antivenom has no definite role in Elapid ophitoxaemia [66]. They emphasized the role of anticholinesterase and supportive care as cornerstones of management. In view of the large number of dry bites observed in a Brazilian study, the authors recommended that antivenom be postponed or not administered to victims presenting with no manifestations of local or systemic envenomation [67].

Dose

Despite widespread use of antivenom, there are virtually no clinical trials to determine the ideal dose [68]. Conventionally 50 ml (5 vials) is infused for mild manifestations like local swelling with or without lymphadenopathy, purpura or echymosis. Moderate envenomation defined by presence of coagulation defects or bradycardia or mild systemic manifestations, merits the use of 100 ml (10 vials). 150 ml (15 vials) is infused in severe cases, which includes rapid progression of systemic features, DIC, encephalopathy and paralysis [16].
Thomas and Jacob have attempted to study the effect of a lower dose in a randomized controlled trial and established that, in a cohort of patients who received half the conventional dose, there is no significant difference in the time taken for clotting time to normalize [68]. Philip also advocates using lower doses than conventionally used [1].
Based on a study of 24 cases of demonstrated Russell's viper venom antigenemia, wherein the mean amount of monospecific antivenom correcting blood incoagualability was 165 (59.3 ml, it has been recommended that 60 ml be administered intravenously at 6 hourly intervals till blood coagulability is restored [69]. This dose appears to have been appropriate in a group of Nepalese patients, wherein 71% received less than 6 vials per patient [14]. Theoretically, there does not seem to be an upper dose limit and even 45 vials (4500 units) have been used successfully in a patient [14].

Administration

The freeze dried powder is reconstituted with 10 ml of injection water or saline or dextrose . A test dose is administered on one forearm with 0.02 ml of 1:10 solution intradermally. Similar volume of saline in the other forearm serves as control. Appearance of erythema or wheal greater than 10 mm within 30 min is taken as a positive test [16]. In this event, desensitization is advised starting with 0.01 ml of 1:100 solution and increasing concentration gradually at intervals of 15 minutes till 1.0 ml s.c can be given by 2 hours [16]. Infusion is started at 20 ml/kg per hour initially and slowed down later [16].

Antivenom is administered by the intravenous route [16] and never into fingers or toes [27]. Some authors recommend that 1/3 to 1/2 the dose be given at the local site to neutralize venom there (De Vries) [27]. However, animal experiments have established that absorption begins almost instantly from bite sites. Besides this, systemic administration of antivenom has been shown to be effective at the local site as well. Therefore most experts do not advise local injection of antivenin [27]. Efficacy of intramuscular administration of antivenom followed by standard hospital management has also been evaluated and a definite reduction in the number of patients with systemic envenomation, complications and mortality from Russell's viper toxemia has been noted [71]. This route of administration is likely to have value in a field setting prior to transfer to better facilities.

Timing

There is no consensus as to the outer limit of time of administration of antivenom. Best effects are observed within four hours of bite [16]. It has been noted to be effective in symptomatic patients even when administered up to 48 hours after bite. Reports suggest that antivenom is efficacious even 6-7 days after the bite [72]. This is corroborated by Saini's observations also [73]. In experimental settings, rats injected with antivenom even 3 weeks after the bite showed good response [74]. It is obvious that when indicated, antivenom must be administered as early as possible and data showing efficacy with delayed administration is based on use in settings where patients present late.
Response

Response to infusion of antivenom is often dramatic [16] with comatose patients sitting up and talking coherently within minutes of administration. Normalization of blood pressure is another early response [70]. Within 15 to 30 minutes, bleeding stops though coagulation disturbances may take up to 6 hours to normalize. Neurotoxicity improves from the first 30 minutes but may require 24 to 48 hours for full recovery [8].
If response to antivenom is not satisfactory use of additional doses is advocated. However, no studies establishing an upper limit are available [14] infusion may be discontinued when satisfactory clinical improvement occurs even if recommended dose has not been completed [21]. In experimental settings, normalization of clotting time has been taken as end-point for therapy.

Reactions

Hypersensitivity reactions including the full range of anaphylactic reactions may occur in 3-4% of cases, usually within 10 to 180 minutes after starting infusion. These usually respond to conventional management including adrenaline, anti-histamines and corticosteroids [17].

Availability

Several antivenom preparations are available internationally. In India, polyvalent antivenom prepared by C.R.I., Kasauli is effective against the 4 commonest species [16]. Antivenom produced at the Haffkine Corporation, Parel includes more species as well. This is about 10 times as expensive as the former.
The WHO has designated the Liverpool School of Tropical Medicine as the international collaborating centre for antivenom production and/or testing.

Supportive Therapy

In cases of bleeding, replacement with fresh whole blood is ideal. Fresh frozen plasma and fibrinogen are not recommended.
Volume expanders including plasma and blood are recommended in shock, but not crystalloids [16]. Persistent shock may require inotrope support under CVP monitoring [16]. Early mechanical ventilation is advocated in respiratory failure though dramatic responses have also been observed with edrophonium followed by neostigmine [29]. Cases of acute renal failure generally respond to conservative management. Occasionally peritoneal dialysis may be necessary. In cases of DIC, use of heparin should be weighed against risk of bleeding and hence caution is advocated [1].
Routine antibiotic therapy is not a must [28] though most Indian authors recommend use of broad spectrum antibiotics [16]. Chloramphenicol has been claimed to be useful as a post bite antibiotic even when used orally since it is active against most of the aerobic and anaerobic bacteria present in the mouths of snakes. Alternatives include cotrimoxazole, flouroquinolones with or without metronidazole or clindamycin for anaerobic cover [62]. A study of the organisms isolated from the mouth of the Malayan pit vipers suggests that crystalline penicillin with gentamicin would also be appropriate antibiotic cover following snakebite [75].
Recent studies have reported the beneficial effects of intravenous immunoglobulin (IVlg) in ophitoxaemia. There are suggestions that its administration may improve coagulopathy, though its effect on neurotoxicity is questionable. A pilot study indicates that IVIg with antivenom eliminates the need to repeat antivenom for envenomations associated with coagulopathy [76].
A compound extracted from the Indian medicinal plant Hemidesmus indicus R (2-hydroxy-4 methoxy benzoic acid [77] has been noted to have potent anti-inflammatory, antipyretic and anti-oxidant properties, particularly against Russell's viper venom [78]. These experiments suggest that chemical antagonists from herbs hold promise in the management of ophitoxaemia; particularly when used in the presence of antivenom.
Four cases of tetanus have been documented following snake-bite [27] hence tetanus toxoid is a must. Early surgical debridement is generally beneficial [16,70] though fasciotomy is usually more harmful than useful [16,70]. There is no role for steroid therapy in acute snake bite [27]. Although it delays the appearance of necrosis, it does not lessen the severity of outcome [29].

Conclusion

Snakes do not generally attack human beings unprovoked. They are reputed to be more afraid of man than vice-versa. Nevertheless once bitten, a wide spectrum of clinical manifestations may result. The emphasis for treatment should be placed on early and adequate medical management. Overemphasis on first-aid can be dangerous because its value is debatable and too much valuable time is wasted in its administration.

COMMON SNAKE MYTHS IN INDIA

The Snake is a powerful symbol in Indian mythology and Hinduism. The 'Nag' is worshipped by people across the country. Some of these mythical snakes are protectors, while others are destroyers. The picture of Lord Shiva is incomplete without the cobra around his neck, and Lord Vishnu rests on a seven headed snake. There are hundreds of references to snakes with mythical powers in stories and epics. This has made snakes a powerful symbol in the Indian culture. But there are thousands of beliefs and myths surrounding snakes, widespread in the country, which are misleading. Most of them are spread by the snake charmers. During our snake rescues, our team members are showered with questions such as "Do snakes drink milk?" or "Is there a two headed snake?"

To know more about the truth continue reading..
Myth: Rat Snakes are poisonous.
Scientific Facts: - Rat snakes are NON POISONOUS, rodent eating reptiles.

Myth: Rat Snakes mate with cobras.
Scientific Facts: - Rat Snakes or any other snakes will not mate with any snake out of its own species. Cobras eat other snakes so a mating between a cobra and a rat snake is not possible.

Myth: Snakes drink Milk
Scientific Facts: - Snakes do not drink milk, neither can they digest it properly. They are reptiles and have no association with milk, only mammals who have mammary glands can produce milk and thus, a liking for milk in non mammals is unlikely. But in a crises when severely dehydrated, a snake might drink any liquid available.

Myth: - Some snakes grow a beard as they get older
Scientific Facts: - Snakes are reptiles and do not have any hair on their bodies let alone a beard. It is impossible for them to have beards for their bodies do not have any ability of growing hair.

Myth: - Snakes carry a diamond in their forehead
Scientific Facts: - It is impossible for a snake to carry anything in its head. The mythological status attached with a snake in India is probably responsible for this myth.

Myth: -Snakes remember you if you hurt it.
Scientific Facts: - Snakes are not vengeful animals and do not have the necessary intelligence to remember people or places for getting revenge. Hindi Movies have a lot to do with the creation of this myth

Myth: -If one snake is killed its partner will trace you (no matter wherever you are)
Scientific Facts: - Once again snakes are not vengeful animals and are not interested in chasing or tracing people who hurt them. They do not have the necessary memory and intellect to remember people to trace them back. Neither do snakes have a feeling of camaraderie or pair for life. Once again bollywood is responsible for this myth.

Myth: -Flying snakes can pierce somebody’s forehead or put out their eyes.
Scientific Facts: - A flying snake does not actually fly but only glide through the air by extending ribs and pulling in the underside. It can glide a distance of 330 Ft or 100 mt. It has an elongated head, which gives the scary feeling that it can pierce a person’s head or eyes.

Myth: - Snakes found in India can spit venom.
Scientific Facts: - No snake found in India can spit venom. Only spitting Cobras can spit venom and they are not found in India.

Myth:-There are “Two- headed” snakes.
Scientific Facts: - The snake charmers spread the myth about the two headed snakes only to maintain the mythological status of the snakes in India so they can continue attracting large crowds to their snake shows. In reality nothing as a two headed snake exists.

FATHER OF INDIAN OPHIOLOGY - Dr. Patrick Russell

Dr Patrick Russell (6 February 1726, Edinburgh - 2 July 1805) was a Scottish surgeon and naturalist who worked in India. He studied the snakes of India and is considered the 'Father of Indian Ophiology'. The Russell's viper, Daboia russelii, is named after him.

Russell travelled to Vishakapatnam, India in 1781 at the age of 54 to look after his brother who worked with the East India Company. He took a great interest in the plants of the region leading to his appointment in 1785 as the company's 'Botanist and Naturalist' in the Government of Madras. This post, according to Ray Desmond (1992, European Discovery of Indian Flora) was:

The Company's expectations of their Naturalist were excessively optimistic. He was presumed to be a linguist, demographer, antiquarian, meteorologist, mineralogist and zoologist (in addition to being a botanist).

He was a keen observer and skilled in clinical practice and he applied his medical skills in Aleppo, Syria, during an outbreak of the plague. He wrote about the plant and animal life of Aleppo as well as the Madras Province of India. As a physician as well as Naturalist to the East India Company in the Carnatic he was concerned with the problem of snakebite. His aim was to find a way for people to identify poisonous snakes.

Russell spent six years in the Madras presidency. He sent a large collection of snakes in 1791 to the British Museum. He wrote a two volume work An Account of Indian Serpents Collected on the Coast of Coromandel which included drawings done by him. Part of the work was published posthumously. He also made a large collection of plants.

Blind pink snake discovered in Madagascar

A pink worm-like snake has been rediscovered in Madagascar more than 100 years after it was first found. The snake, which is blind and measures about ten inches long, is described in the February 1, 2007 edition of Zootaxa, a leading taxonomic journal.

The snake was captured during a 2005 expedition in the arid northern part of the country. It was collected by Vincenzo Mercurio from the Forschungsinstitut und Naturhistorisches Museum Senckenberg in Germany and described as a new species by Dr. Van Wallach from the Museum of Comparative Zoology Harvard University.

"The finding of this new typhlopid species indicates, once more, that most of the Malagasy herpetofauna is highly secretive, and in general difficult to be detected. It is amazing that the genus Xenotyphlops remained unconfirmed for more than one century, despite the many field surveys conducted in Madagascar," wrote the authors. "More surprising was that the newly found individual belonged to a different species."

The snake, named Xenotyphlops mocquardi, is one of 15 blind snakes species known from Madagascar. Blind snakes live underground or beneath a layer of rocks, sand, or leaves and rarely emerge from their hideouts. They have poor eyesight and rely primarily on smell and heat detection to locate their prey consisting of insects and insect larvae.


Xenotyphlops mocquardi, Photo by Vincenzo Mercurio
The authors said they hope the snake's habitat is incorporated into a planned protected area.

"We hope that more individuals of Xenotyphlops mocquardi will be found in the future," they wrote. "Taken into consideration the high reptile endemism detected at the latter locality... it is suggested that Montagne des Français / Ambodivahibe should be included in the forthcoming protected area network for the safeguard of his rocky forested slopes and of the dry bushy savannah hosting an unique herpetofauna."

A Few Notes on Sea Snakes(taken from the Oceana Network)

One of the greatest threats to the health of marine ecosystems and the viability of many marine species is the commercial discarding of species that are deemed to have little or no economic value.

One group of marine animals that are too often given short shrift by marine managers, academics, and the public at large, could be considered invisible victims of commercial fishing operations in the Indo-Pacific oceans, where significant levels of bycatch and discarding occurs.

Sea snakes are the most abundant and widely dispersed group of poisonous reptiles in the world. Approximately 70 species of sea snakes live throughout the warm tropical waters of the Indo-West Pacific (they are not found in the Atlantic Ocean or Caribbean Sea) and account for 86 percent of marine reptile species alive today.

Rattlesnakes

Representative Sonoran Desert species:

western diamondback (Crotalus atrox)
mohave rattlesnake (Crotalus scutulatus)
tiger rattlesnake (Crotalus tigris)
blacktail rattlesnake (Crotalus molossus)
sidewinder (Crotalus cerastes)

Order: Squamata
Family: Viperidae (moveable front-fang venomous snakes)
Spanish names: víbora de cascabel (rattlesnake), víbora de cuernitos (sidewinder)
Distinguishing Features

Western diamondback: Dark, diamond-shaped or hexagonal blotches along the center of the back, light eye stripe from eye to upper lip, bold black and white tail banding, small scales on head.

Mohave rattlesnake: Difficult to distinguish from western diamondback; tail generally has narrower black bands than white, 2 to 3 enlarged scales on top of the head between the eyes.

Tiger rattlesnake: Small head and large rattle, 35 to 52 distinct closely-spaced crossbands on back and sides. Blacktail rattlesnake: Black tail and snout.

Sidewinder: Horn-like projection over each eye.
Habitat

The western diamondback is a generalist which can be found in diverse habitats from below sea level to 6500 feet (2000 m). The Mohave rattlesnake prefers open areas with grasses, creosote bush, palo verde, mesquite and cactus; most common at lower elevations; also common in desert grasslands of southeast Arizona; usually not present in rocky areas or areas with heavy vegetation. The tiger rattlesnake is strictly a Sonoran Desert region species; most common in very rocky canyons and foothills or arid desert mountains up to 4800 feet (1460 m); usually restricted to cactus and mesquite of the rocky foothills; seldom encountered in flat, sandy areas devoid of rocks. The blacktail is primarily a mountain snake found in pinyon-oak woodland or coniferous forests up to 9600 feet (2900 m) near rocky areas; also resides in saguaro-covered desert uplands. The Sidewinder is a common resident of sand dunes and other loose, sandy areas where vegetation is sparse and composed primarily of creosote bush; rarely seen in rocky areas.

Click here to hear rattlesnake sounds
Blacktail rattlesnake
Feeding

• Diet: Rodents make up the majority of the diet for all of these snakes. Birds, lizards and other small animals are also taken.
Life History

Western diamondback: This snake is active at night during the warm months and during the day in spring and fall; it returns to rocky cliffs for a winter hibernation period, but may exit to bask in the sun on warm days.

Mohave Rattler
The Mohave rattlesnake may be the most dangerous venomous snake in the Sonoran Desert. Quick to go on the defensive, the Mohave has very toxic venom that has caused human fatalities. Venom toxicity varies among different populations. The seriousness of a bite from this rattlesnake, as from any rattlesnake, depends on many factors, including, but not limited to, the amount of venom injected and the health and size of the victim. A person bitten by a Mohave rattlesnake should seek medical attention immediately.

Prior to copulation in the spring, male diamondbacks (as well as males of at least some other rattlesnake species) perform well-documented, ritualized “combat dances.” When two males encounter each other they raise their bodies off the ground—as much as one-third of their lengths. Belly-to-belly, they begin an intense wrestling contest. Occasionally one snake or the other falls to the ground, only to rise up to continue the contest anew. This wrestling match may continue for thirty minutes or more. At some point, one snake finally gives up and crawls away, often with the victor in hot pursuit. Victors have even been observed climbing into shrubs several feet off the ground, apparently to make sure the loser does not try to return to the females. There are occasions when a third male is present. He does not join the duo at battle, but instead copulates with the females while the other two males are battling. Biologists have termed this the “sneaky male strategy.” The inseminated female will give birth to as many as 23, 9- to 14-inch-long (23-36 cm) young in the late summer. Young diamondbacks feed on rodents, and adults also eat rabbits and ground-dwelling birds.

Mohave rattlesnake: The Mohave is active primarily at night from February to November. Unlike most rattlesnakes, which usually hibernate in larger groups, the Mohave hibernates singly or in pairs or trios in rodent burrows. Courtship and copulation occur in the spring or, occasionally, in the fall. Following fall copulation, sperm may be viably retained for several months, resulting in births during the next year’s warmer seasons. As many as 13, 9-inch-long (23 cm) young are usually born in late summer and early fall. Rodents comprise the bulk of the diet.

Tiger rattlesnake: While this snake is active from spring through late fall, its peak of activity correlates with the summer monsoons. Though not rare, it is rarely seen; it is primarily nocturnal. Mating occurs in April, with 4 to 6, 9-inch-long (23 cm) young born late June through September. The tiger rattlesnake fang is proportionately shorter than that of other rattlesnakes; the venom is strong. Tiger rattlesnakes eat lizards and rodents; juveniles generally favor lizards more than do adults. Though these are small rattlesnakes, they have been known to eat fairly large prey, including kangaroo rats, packrats, and even spiny lizards!
Sidewinder

Blacktail rattlesnake: This snake often climbs into the lower branches of trees and shrubs several feet off the ground to bask in the sun or to feed on birds. It also readily eats mammals and lizards. Born in mid-summer, the young number 3 to 16, about 1 foot long (30 cm). Like many rattlesnakes, the blacktail is not aggressive nor easily alarmed and may not rattle if approached.

Sidewinder: Where it is warm throughout the year, the sidewinder is active year-round. During the summer the sidewinder seeks shelter during the day, retreating to animal burrows or burying itself in the sand under the shade of a creosote bush. It ventures out at night to eat lizards, small snakes, birds and mammals. During cooler seasons sidewinders may be diurnal (active during the day) or crepuscular (active at dusk or dawn). In areas where hibernation does occur, the sidewinder hibernates singly in a rodent burrow, or occasionally in a desert tortoise burrow. Copulation occurs in the spring, and 5 to 18 young, 6¼ to 8 inches (16-20 cm) long, are born in late summer and fall.
Sidewinding

While many snakes use the method of locomotion called “sidewinding, ”the sidewinder is particularly adept at it. Sidewinding is a method of locomotion adapted for areas with loose, hot, sandy soils where traction is difficult. To sidewind, the snake throws a loop of its body forward and then pulls itself up on the loop. As the loop is thrown forward, the head and neck of the snake push down into the sand. In this way much of the snake’s body is held up off the hot surface. To the observer, the sidewinding snake appears to be going sideways with respect to the direction in which the body points. While sidewinding is the primary form of locomotion for a sidewinder, it can also use all other methods of locomotion characteristic of snakes.