Black mamba

Black mamba

The African Black mamba (Dendroaspis polylepis) is a large and highly venomous snake species native to much of Sub-Saharan Africa. It is the second longest venomous snake species in the world and is the fastest moving land snake, capable of moving at 4.32 to 5.4 metres per second (16–20 km/h, 10–12 mph). It is by far the most feared and most dangerous snake species in Africa and it has a legendary reputation as a very fierce and territorial snake. When cornered or threatened, the black mamba can put up a fearsome display of defense and aggression. A black mamba will often mimic a cobra by spreading a neck-flap; exposing its black mouth, raising its body off the ground, and hissing. It can rear up around one-third of its body from the ground, which can put it at about four feet high. When warding off a threat, the black mamba delivers multiple strikes, injecting large amounts of virulently toxic venom with each strike, often landing bites on the body or head, unlike other snakes. Their strikes are very quick and extremely accurate and effective.If the attempt to scare away the threat fails, it will strike repeatedly.  This species of snake often shows an incredible amount of tenacity, fearlessness, and aggression when cornered or threatened, during breeding season, or when defending its territory. They are also known to have a 100% rate of envenomation. The probability of dry bites (no venom injected) in black mamba strikes is almost non-existent. The venom of the black mamba is a protein of low molecular weight and as a result is able to spread extraordinarily rapidly within the bitten tissue. The venom of this species is the most rapid-acting venom of any snake species and consists mainly of highly potent neurotoxins; it also contains cardiotoxins , fasciculins and calciseptine.

Based on the Median lethal dose (LD₅₀) values in mice, the black mamba LD₅₀ from all published sources is as follows:

·         (SC) subcutaneous (most applicable to real bites): 0.32 mg/kg, 0.28 mg/kg.

·         (IV) intravenous: 0.25 mg/kg, 0.011 mg/kg.

·         (IP) intraperitoneal: 0.30 mg/kg (average), 0.941 mg/kg. 0.05 mg/kg (the last quote doesn't make it clear if is either intravenous or intraperitoneal).

It is estimated that only 10 to 15 mg will kill a human adult; however, its bites deliver about 120 mg of venom on average, although they may deliver up to 400 mg of venom in a single bite. If bitten, severe neurotoxicity invariably ensues rapidly. This is due to several factors that include the high potency of their venom, the unique composition of synergistic toxins contained within the venom which bring on severe symptoms of envenomation and death much faster than any other venomous snake in the world. In addition, the species itself possesses the most advanced, evolved, and efficient venom delivery apparatus among all venomous snakes, and the most advanced and evolved dentition of all elapids. Black mambas possess the longest fangs of any elapid, averaging around 13.1 millimeters (0.52 in), but may grow as long as 22 millimeters (0.87 in). Another feature which distinguishes the dentition and the venom delivery apparatus of this species from all other elapids and other species of venomous snake, including those of the family Viperidae is the fact that the fangs are positioned very forward at the most-anterior position possible in its mouth - right up in the front of its upper jaw. The proteins in black mamba venom are of extremely low molecular weight, low viscosity, and the venom's very high activity in terms of hyaluronidases, which is also essential in facilitating dispersion of venom toxins throughout tissue (spreading the venom through the body) by catalyzing the hydrolysis of hyaluronan, a constituent of the extracellular matrix (ECM), hyaluronidase lowers the viscosity of hyaluronan, and Dendroaspin natriuretic peptide (DNP), a newly discovered component of mamba venom, is the most-potent natriuretic peptide and it's unique to the genus Dendroaspis, or mambas. It is a polypeptide analogous to the human atrial natriuretic peptide; it is responsible for causing diuresis through natriuresis and dilating the vessel bloodstream, which results in, among other things, acceleration of venom distribution in the body of the victim, thereby increasing tissue permeability. These advanced and highly evolved physical and biological features combined with this species' large size, explosive aggression, and quickness make the black mamba a terrifying adversary. Neurological, respiratory, andcardiovascular symptoms rapidly begin to manifest, usually within less than ten minutes. Common symptoms are rapid onset of dizziness, drowsiness, headache, coughing or difficulty breathing, convulsions, and an erratic heartbeat. Other common symptoms which come on rapidly include neuromuscular symptoms, shock, loss of consciousness, hypotension, pallor, ataxia, excessive salivation (oral secretions may become profuse and thick), limb paralysis, nausea and vomiting, ptosis, fever, and very severe abdominal pain. Local tissue damage appears to be relatively infrequent and of minor severity in most cases of black mamba envenomation. Edema is typically minimal. Acute renal failure has been reported in a few cases of black mamba bites in humans as well as in animal models. The venom of this species has been known to cause permanent paralysis in some cases. Death is due to suffocation resulting from paralysis of the respiratory muscles. Untreated black mamba bites have a mortality rate of 100%. Antivenomtherapy is the mainstay of treatment for black mamba envenomation. A polyvalent antivenom produced by the South African Institute for Medical Research (SAIMR) is used to treat all black mamba bites from different localities. Due to antivenom, a bite from a black mamba is no longer a certain death sentence. But in order for the antivenom therapy to be successful, vigorous treatment and large doses of antivenom must be administered very rapidly post-envenomation. In case studies of black mamba envenomation, respiratory paralysis has occurred in less than 15 minutes. Envenomation by this species invariably causes very severe neurotoxicity due to the fact that black mambas often strike repeatedly in a single lunge, biting the victim up to 12 times in extremely rapid succession. Such an attack is very fast, lasting less than one second and so it appears to be a single strike and single bite. With each bite the snake delivers anywhere from 100 to 400 mg of a rapid-acting and virulently toxic venom. As a result, the doses of antivenom required are often massive (10–30+ vials) for bites from this species. Although antivenom saves many lives, mortality due to black mamba envenomation is still at 14%, even with antivenom therapy. In addition to antivenom therapy, endotracheal intubation and mechanical ventilation are required for supportive therapy.