<P> The common krait (Bungarus caeruleus) is often considered to be the most dangerous snake species in India . Its venom consists mostly of powerful neurotoxins which induce muscle paralysis . Clinically, its venom contains pre synaptic and postsynaptic neurotoxins, which generally affect the nerve endings near the synaptic cleft of the brain . Due to the fact that krait venom contains many presynaptic neurotoxins, patients bitten will often not respond to antivenom because once paralysis has developed it is not reversible . This species causes an estimated 10,000 fatalities per year in India alone . There is a 70 - 80% mortality rate in cases where there is no possible or poor and ineffective treatment (e.g., no use of mechanical ventilation, low quantities of antivenom, poor management of possible infection). Average venom yield per bite is 10 mg (Brown, 1973), 8 to 20 mg (dry weight) (U.S. Dept . Navy, 1968), and 8 to 12 mg (dry weight) (Minton, 1974). The lethal adult human dose is 2.5 mg . In mice, the LD values of its venom are 0.365 mg / kg SC, 0.169 mg / kg IV and 0.089 mg / kg IP . </P> <P> Russell's viper (Daboia russelii) produces one of the most excruciatingly painful bites of all venomous snakes . Internal bleeding is common . Bruising, blistering and necrosis may appear relatively quickly as well . The Russell's viper is irritable, short - tempered and a very aggressive snake by nature and when irritated, coils tightly, hisses, and strikes with lightning speed . This species is responsible for more human fatalities in India than any other snake species, causing an estimated 25,000 fatalities annually . The LD in mice, which is used as a possible indicator of snake venom toxicity, is as follows: 0.133 mg / kg intravenous, 0.40 mg / kg intraperitoneal, and about 0.75 mg / kg subcutaneous . For most humans, a lethal dose is approximately 40--70 mg . However, the quantity of venom produced by individual specimens is considerable . Reported venom yields for adult specimens range from 130--250 mg to 150--250 mg to 21--268 mg . For 13 juveniles with an average length of 79 cm, the average venom yield was 8--79 mg (mean 45 mg). </P> <P> The Saw - scaled viper (Echis carinatus) is small, but its unpredictability, aggressive temper, and lethal venom potency make it very dangerous . This species is one of the fastest striking snakes in the world, and mortality rates for those bitten are very high . In India alone, the saw - scaled viper is responsible for an estimated 5,000 human fatalities annually . However, because it ranges from Pakistan, India (in rocky regions of Maharashtra, Rajasthan, Uttar Pradesh and Punjab), Sri Lanka, parts of the Middle East and Africa north of the equator, is believed to cause more human fatalities every year than any other snake species . In drier regions of the African continent, such as sahels and savannas, the saw - scaled vipers inflict up to 90% of all bites . The rate of envenomation is over 80% . The saw - scaled viper also produces a particularly painful bite . This species produces on the average of about 18 mg of dry venom by weight, with a recorded maximum of 72 mg . It may inject as much as 12 mg, whereas the lethal dose for an adult human is estimated to be only 5 mg . Envenomation results in local symptoms as well as severe systemic symptoms that may prove fatal . Local symptoms include swelling and intense pain, which appear within minutes of a bite . In very bad cases the swelling may extend up the entire affected limb within 12--24 hours and blisters form on the skin . Of the more dangerous systemic symptoms, hemorrhage and coagulation defects are the most striking . Hematemesis, melena, hemoptysis, hematuria and epistaxis also occur and may lead to hypovolemic shock . Almost all patients develop oliguria or anuria within a few hours to as late as 6 days post bite . In some cases, kidney dialysis is necessary due to acute renal failure (ARF), but this is not often caused by hypotension . It is more often the result of intravascular hemolysis, which occurs in about half of all cases . In other cases, ARF is often caused by disseminated intravascular coagulation . </P> <P> The Fer - de-lance or Terciopelo (Bothrops asper) has been described as excitable and unpredictable when disturbed . They can, and often will, move very quickly, usually opting to flee from danger, but can suddenly reverse direction to vigorously defend themselves . Adult specimens, when cornered and fully alert, should be considered dangerous . In a review of bites from this species suffered by field biologists, Hardy (1994) referred to it as the "ultimate pit viper". Venom yield (dry weight) averages 458 mg, with a maximum of 1530 mg (Bolaños, 1984) and an LD in mice of 2.844 mg / kg IP . This species is an important cause of snakebite within its range . It is considered the most dangerous snake in Costa Rica, responsible for 46% of all bites and 30% of all hospitalized cases; before 1947, the fatality rate was 7%, but this has since declined to almost 0% (Bolaños, 1984), mostly due to the Clodomiro Picado Research Institute, responsible for the production of antivenom . In the Colombian states of Antioquia and Chocó, it causes 50 - 70% of all snakebites, with a sequelae rate of 6% and a fatality rate of 5% (Otero et al., 1992). In the state of Lara, Venezuela, it is responsible for 78% of all envenomations and all snakebite fatalities (Dao - L., 1971). One of the reasons so many people are bitten is because of its association with human habitation and many bites occur indoors (Sasa & Vázquez, 2003). </P>

Which is the most poisonous snakes in the world