Tuesday, October 5, 2010

The Bite of the Greater Black Krait

The Greater Black Krait (Bungarus niger) was previously known from India, Nepal, Bhutan and Burma, but it is now known to be widespread in Bangladesh. It was described by Frank Wall in 1908 from Assam and Darjeeling, but it has been found to be widespread in northeast India where it uses a variety of habitats ranging from grassland to forest and leaf litter to rock outcrops. The Greater Black Krait  occurs at elevations of 200 to 1450 m. No known bites from this snake were previously reported. Now,  Faizet al. (2010) describe five cases of envenomation from Bangladesh. The index case presented symptoms of typical neurotoxic envenoming produced by all kraits, descending flaccid paralysis. But the patient later developed generalized rhabdomyolysis (the breakdown of muscle fibers) with the associated presence of myoglobin in his urine (myoglobinuria) and acute renal failure  which resulted in death. Of the other four patients, one died of respiratory paralysis and three recovered after developing paralysis, requiring mechanical ventilation in one patient. One patient suffered severe generalized muscle pain and painful swallowing associated with increased creatine kinase concentration in his serum. These are the first reported cases of rhabdomyolysis resulting from envenoming by any terrestrial Asian elapid snake. However, the literature suggested that venoms from some populations of Bungarus candidus and Bungarus multicinctus in Thailand and Vietnam may also have this effect in human victims. The authors investigated this unexpected property of Bungarus niger  venom from a snake responsible for one of the human cases. Venom was injected into one hind limb of rats and saline into the other under an analgesic. All animals developed paralysis of the venom-injected limb within two hours. Twenty-four hours later, the soleus muscles were compared and the results showed the pre-synaptic action (β-bungarotoxins) of Bungarus niger venom at the neuromuscular junctions. This resulted in loss of synaptophysin and the degeneration of the motor innervation of the rat's skeletal muscle. Swelling and necrosis confirming the myotoxic effect of the venom, attributable to phospholipases A2.

Md Abul Faiz, Aniruddha Ghose, Md Farid Ahsan, Md Ridwanur Rahman, Md Robed Amin, Md Mahtab Uddin Hassan, Md A. Wahed Chowdhury, Ulrich Kuch, Thalita Rocha, John B. Harris, R. David G Theakston, and David A. Warrell. 2010. The greater black krait (Bungarus niger), a newly recognized cause of neuro-myotoxic snake bite envenoming in Bangladesh. Brain, A Journal of Neurology doi:10.1093/brain/awq265

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