SNAKES OF MEDICAL IMPORTANCE
Bites by green pitvipers (Cryptelytrops erythrurus and other species), cobras (Naja species) and kraits (Bungarus) are the most commonly identified ones in Bangladesh. Neurotoxic envenoming by kraits and cobras is the principal cause of snake bite mortality in Bangladesh.
Recent studies revealed that at least five different species of krait contribute to snake bite mortality in Bangladesh and Nepal (unpublished data). Based on their frequencies among proven krait bites in Bangladesh and their geographical distribution, we presently estimate that Wall’s Krait (Bungarus walli) causes about 40% of all krait bites in the country, the Greater Black Krait (Bungarus niger) and the Common Krait (Bungarus caeruleus) about 28% each, and the Banded Krait (Bungarus fasciatus) and Lesser Black Krait (Bungarus lividus) about 2% each. In Bangladesh, Bungarus lividus is so far known only from the northwest. Bungarus walli and B. caeruleus are not known to occur in southeastern Bangladesh. Bungarus fasciatus and B. niger occur throughout the country.
Among the cobras, Naja kaouthia is expected to occur throughout the country and to cause the majority of cobra bites. It is the only species of Naja found in southeastern Bangladesh (here defined to include Chittagong District, Cox’s Bazar District, and the three Chittagong Hill Tract Districts). Naja naja is known from the area around Dhaka and expected to be continuously distributed at least to the west and north of the capital. Its southern and eastern distributional limits are not known. King Cobras (Ophiophagus hannah) occur wherever relatively undisturbed bamboo stands and forests remain in Bangladesh, but have not been documented to have caused envenoming bites in recent years.
Russell’s Viper (Daboia russelii) appears to be rare and its distribution patchy and/or restricted to western and northern parts of the country. There have been no recent reports of proven cases of Russell’s Viper envenoming in Bangladesh. Anecdotal notes (Banerji 1929) suggest that envenoming by Russell’s viper used to occur in the southwest (Assasuni and Shamnagar in Satkhira District; Koyra and Paikgacha in Khulna District) and possibly around Rajshahi and Dinajpur in the west and northwest of Bangladesh. There is no evidence to suggest that Saw-scaled Vipers (Echis species) occur anywhere in Bangladesh.
Sea snakes also constitute an occupational hazard for fishermen in Bangladesh but the incidence of their bites is unknown.