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Echis Carinatus, Saw-scaled viper, is a venomous viper species found in parts of the Middle East and Central Asia, and especially the Indian subcontinent. It is the smallest member of the Big Four snakes (Indian Cobra, Naja naja, Common krait, Bungarus caeruleus; Russell's viper, Daboia russelii; Saw-scaled viper, Echis carinatus) that are responsible to cause the most snakebite cases and deaths, due to various factors including their frequent occurrence in highly populated regions, and their inconspicuous nature. Size ranges between 38 and 80 cm (15-31.5 inches) in total length (body + tail), but usually no more than 60 cm (23.5 in).
E. carinatus is endemic to Asia, it is found in the Indian subcontinent (for example in Pakistan), in the Middle East (i.e. Oman) and In Central Asia (Afghanistan, Uzbekistan, Turkmenistan etc.).
Its prey usually are rodents, lizards, frogs, and a variety of arthropods, such as scorpions, centipedes and large insects.
Venom
This species produces on the average about 18 mg of dry venom by weight, with a recorded maximum of 72 mg. It may inject up to 12 mg, whereas the lethal dose for an adult is estimated to be only 5 mg. Envenomation results in local symptoms as well as severe systemic symptoms that may be fatal. Local symptoms include swelling and pain, which appear in few minutes after its bite. In worst cases the swelling may extend up the entire affected limb within 12–24 hours and blisters form on the skin. The venom yield from individual specimens varies considerably, as does the quantity injected per bite. The mortality rate from their bites is about 20%, and due to the availability of the anti-venom, deaths are currently quite rare.
Hemorrhage and coagulation defects are the most striking among the systemic symptoms. 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.
This venom can be a rich source of protein with various factors affecting the plasma protein and blood coagulation factor. The venom from this species is used in the manufacture of several drugs, for instance Tirofiban.
Induction of blood coagulation in vitro
Blood coagulation induced by Iranian saw-scaled viper (Echis carinatus) venom: identification, purification and characterization of a prothrombin activator, November 2013
This study showed that the fraction which separated from Iranian snake E. carinatus venom can be a prothrombin activators. It can be concluded that this fraction is a procoagulant factor. This study has investigated the venom of Iranian E. carinatus which contains a strong procoagulant factor enabling to activate the prothrombin. In the present study, crude venom from the Iranian snake E. carinatus was selected and assayed with PT test. The PT test was reduced from 13.4 s to 8.6 s when human plasma was treated with crude venom (concentraion of venom was 1 mg/ml). Its venom also displays coagulation properties and increases the blood coagulation cascade.
The purified procoagulant factor revealed a single protein band in SDS polyacrylamide electrophoresis under reducing conditions and its molecular weight was estimated at about 65 kDa. A single-band protein showed fragment patterns similar to those generated by the group A prothrombin activators, which convert prothrombin into meizothrombin independent of the prothrombinase complex.
Mikarin is the first group of IA prothrombin activator identified in the venom of a viperidae snake. In the case of prothrombin activator, it exhibited prothrombin activation, which was similar to the other group IA prothrombin activators, such as ecarin from E. Carinatus, aharin from Agkistrodon halys pallas and prothrombin activator from Bothrops atrox many metalloproteinase have been isolated from snake venom with a wide variety of biological activities, including hemorrhagic, fibrinogenolytic and antiplatelet effects, as well as activation of prothrombin and factor X.
In conclusion protein with coagulation activities was purified from the venom of E. Carinatus. Its venom is one of the coagulation venoms whose function is a pseudothromboplastin action. However, in vitro conditions, this venom will generate high coagulation, caused by the activation of the prothrombin. It’s suggested that this venom contains procoagulant factors with molecular weight of about 56 kDa.
THIS RESULTS ARE CONFIRMED BY IN VIVO EVIDENCES
In vivo evaluation of homeostatic effects of Echis carinatus snake venom in Iran, February 2013
Inhibition muscle contraction
Pharmacological and biochemical studies on the venom of a clinically important viper snake (Echis Carinatus) of Pakistan, January 2014
Crude venom showed the presence of disintegrin, PLA2, C-type lectin/lectin-like components, CRISP, Serine protease, l-amino acid oxidase and very high concentrations of SVMPs. E. carinatus venom (1, 10, 30, 50, 100 μg/ml) inhibited the active tension/force of muscle contraction in a time and concentration dependent manner.
| E. Carinatus venom (μg ml−1) | Time to 50% blockadea (min) | Maximum % inhibition (at 120 min) |
| 1 | ≥108.75 ± 8.2601 (4) | 50 |
| 10 | 93.571 ± 9.0444 (7) | 66 |
| 30 | 64.000 ± 4.3012 (5) | 79 |
| 50 | 30.000 ± 3.873 (5) | 86 |
| 100 | 22.000 ± 6.633 (5) | 90 |
Time taken to cause 50% inhibition (t50) and maximum percent inhibition values at 120 min time point of rabbit intestinal active tension induced by different concentrations of E. carinatus snake venom.
The observed effects abolished when the venom was heated at 100 °C for 5 min. However, a decrease in bath temperature from 37 °C to 26 °C or an increase in CaCl2 concentration to 5 mM did not prevent the inhibition of contractile activity. The contractile response elicited by exogenous application of 50 mM KCl and 1 μM acetylcholine (ACh) was also significantly inhibited by all venom concentrations. Prior administration of commercially available polyvalent anti-venom partially neutralized and prevented the effect of E. carinatus venom whereas addition of anti-venom at t50 failed to reverse the inhibitory effect. Studies on isolated intestinal muscle indicate involvement of myotoxic and apoptotic components in E. carinatus venom for irreversible damage to muscle tissue. The different concentrations of E. carinatus venom (1, 10, 30, 50, 100 μg ml−1, n = 5–7) used to monitor contractile activity of rabbit ileum showed significant time and dose dependent inhibition (P < 0.05) in amplitude of active tension (Fig. 2A) when compared with saline. Also significant effect was observed between the groups at higher concentrations from 10 to 120 min. The time point for 50% and maximum percent inhibition at 120 min in the spontaneous active tension of ileum (t50), was also found to be concentration dependent. The response for all venom dilutions was irreversible as spontaneous contractions could not be restored after washing. The active tension decreased slightly (15%) in the control preparation where no venom was added at least for 120 min. The frequency or rate of intestinal contraction by most of the E. carinatus venom concentrations (1, 10, 30, and 50 μg ml−1, n = 5–7) was found to be insignificant ( Fig. 2B) when compared with control experiment. However at concentration of 100 μg/ml the contraction rate was enhanced significantly between the groups after 80–120 min of incubation. In control experiments this parameter was slightly decreased (15%) with increase in time ( Fig. 2B).
E. carinatus venom contains potent bioactive protein components capable of altering both the neuronal and muscular cell membrane properties and causes significant inhibition of active tension. The inhibition of ACh and KCl contractures also depict the presence of both neurotoxic and myotoxic components in the venom of this clinically important snake of Pakistan. This is the first step towards the rational approach in identifying the bioactive principals with a particular effect from any snake species present in the South Asia. Moreover, this study provides the first report of the effect of E. carinatus venom on neuromuscular activity of rabbit intestine and it is further proposed that RINM could also be used as standard preparation for screening the snake venom.
Compliment activation and hemoglobin
In vitro effects of Echis carinatus venom on the human plasma proteome, August 2010
In summary, this study provides insight into the EV proteases active on human plasma proteins. It has been demonstrated that this proteolysis causes a decrease in entire proteins or physiological fragments and generates multiple proteolysis products. The consequences of this protein fragmentation indicate that the coagulation process is most affected by EV poisoning. However, other physiological processes are involved, such as complement activation, hemoglobin metabolism, and molecular transport. The attack of protease inhibitors seems to be a mechanism through which the venom neutralizes the body's defenses. The simultaneous activation of many specific pathological processes contributes to venom toxicity, leading to the death or decay of the entire organism.
