Rabu, 11 Februari 2009

Eastern Brown Snake (Pseudonaja textilis), dangerous snake

The Eastern Brown Snake (Pseudonaja textilis), often referred to as the Brown Snake, is an elapid snake native to Australia. It is one of the world's deadliest snakes. This, combined with a native habitat which includes the well-populated east coast of Australia, has resulted in fatalities. There is a subspecies (Pseudonaja textilis pughi) in parts of New Guinea.

Adult Eastern Brown Snakes are highly variable in colour. Whilst usually a uniform shade of brown, they can have various patternings including speckles and bands, and range from a very pale fawn colour through to black, including orange, silver, yellow and grey. Juveniles have a black head, with a lighter band behind, a black nape, and numerous red-brown spots on the belly. Occasionally they have dark cross-bands. They have 17 rows of mid-body scales, a divided anal scale and 45–75 divided subcaudal scales. Most specimens reach around 1.5 metres in length, with very rare animals exceeding two metres.

Large Eastern Brown Snakes should not be confused with "King Brown" snakes (Pseudechis australis), whose habitat they share, in many areas.

The Eastern Brown Snake is found all the way along the East coast of Australia, from the tip of Cape York, along the coasts and inland ranges of New South Wales, Victoria and South Australia. They are also found in arid areas of the Northern Territory, the far east of the Kimberley in Western Australia and, in very limited numbers, in Papua New Guinea. Due to their mainly rodent diet, they can often be found near houses and farms.

It occupies a varied range of habitats from wet to dry sclerophyll forests (Eucalypt forests) and heaths of coastal ranges, through to savannah woodlands, inner grasslands and arid scrublands. It is not found in rainforests or other wet areas.

The Eastern Brown snake is diurnal (meaning it is active during the day). When highly agitated, they hold their necks high, appearing in an upright S-shape. But despite their fearsome reputation, brown snakes are reluctant to bite and react only to movement; standing still when in close proximity to one will result in it ignoring you. They are attracted to rural and farming areas, probably due to the large numbers of associated rodents. Such areas also normally provide shelter in the form of rubbish and other cover.

Being an opportunistic feeder, the Eastern Brown will consume almost any vertebrate animal, including frogs, lizards, snakes, birds and rodents.

The Eastern Brown Snake is the second most venomous land snake in the world after the Inland Taipan. Although Eastern Browns will seek to avoid confrontation, their venom is very toxic, and can be fatal; even juveniles have caused human fatalities. The venom contains both neurotoxins and blood coagulants.

Despite the potency of the venom, the pressure immobilisation first-aid technique is highly effective (as it is for all Australian venomous snakes). If correct first-aid and safety protocols are followed, the chances of death from Eastern Brown Snake are minimal.

Bites from Pseudonaja affinis (Dugite) most often produces coagulopathy, with other clinical signs including:, abdominal pain, breathing and swallowing difficulty, convulsions, ptosis, hemolysis, hypotension from depression of myocardial contractility, renal failure or rhabdomyolysis. The specific procoagulant involved is a serine protease with a sialic acid component which also contributes to the coagulant action that has a different specific activity than the procoagulants from P. inframacula, P. nuchalis, and P. textilis but has a homologous primary structure.

The ringed-brown snake P. modesta has been reported to cause systemic envenomation but, in contrast with other, more toxic members of the genera, there was a clinical absence of coagulopathy or paralysis with general symptoms being mild.

In direct contrast, P. nuchalis (Gwardar) is an acutely venomous snake capable of causing coagulopathy, hypotension from myocardial damage and renal failure but without neurotoxic symptoms. As previously discussed, the procoagulant is a serine proteases with a sialic acid component, which also contributes to the coagulant action, that has a specific bioactivity but shares sequential homology.

Pseudonaja textilis (Eastern brown snake) is the most toxic member of the genera and, at 12 times the toxicity of the Indian cobra Naja naja, it is the second most toxic land snake in Australia. However, due to the greater range, occurrence in urban areas and aggressive temperament, the eastern brown snake is the most dangerous and clinically important snake in Australia. The venom of the Eastern Brown snake is slow to produce effect, but once symptoms emerge they proceed with terrifying rapidity with death being sudden and unexpected. Part of the problem is that the early signs of the bite pathology closely resemble that of the occurrence of psychological shock and thus may be misdiagnosed. Symptomology of envenomation include: cardiorespiratory failure, disseminated intravascular coagulation accompanied by very active secondary fibrinolysis which contributes to the acute bleeding, renal failure, and severe thrombocytopenia. The coagulant component of the venom is a powerful complete prothrombinase that makes up over 30% of the total venom protein and converts prothrombin to alpha-thrombin which ultimately results in the clinically seen disappearance of fibrinogen and accompanying rise in fibrin in the blood.

Bites are treated with brown snake antivenom.

Eastern Brown Snake (Pseudonaja textilis), dangerous snake Rating: 4.5 Diposkan Oleh: Mel_anie

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