The Western
Ghats of southwestern India is a biodiversity hot spot. The western slopes of
the mountains experience heavy annual rainfall (with most precipitation occurring
from June to September) but the eastern slopes are drier. Rainfall also varies
from north to south producing a wide variation in rainfall patterns and thus a
pattern of vegetation that ranges from scrub forest to tropical
rainforest. Sawant et al. (2010a) examined the distribution and abundance of
pit vipers in five wildlife sanctuaries in Goa using seasonal and day-night
transects to determine habitat use in three pit vipers: the Bamboo Pit Viper (Trimeresurus gramineus), the Malabar Pit
Viper (Trimeresurus malabaricus) and
the Humped-nosed Pit Viper (Hypnale
hypnale). They found specific habitat preferences for each species and note
snake abundance changes with the seasons. The Malabar Pit Viper, Trimeresurus malabaricus, predominantly
occupied tropical semi-evergreen forests and rarely used moist deciduous
forests while the Bamboo Pit Viper, Trimeresurus gramineus and the Humped-nosed Viper, Hypnale hypnale were
mostly in cane brakes, wet bamboo brakes, tropical semi-evergreen, and moist
deciduous forests. Unexpectedly, the Hump-nosed Viper made a remarkable change
in their habitat use. After the monsoon and
into the winter they occupy the cashew plantations adjoining the wildlife sanctuaries.
Hump-nosed Vipers are terrestrial and semi-arboreal and Sawant et al (2010b)
examined its ecology, threats, and conservation. This little pitviper prefers
cool and moist microhabitats. Females using the cashew plantations were more
susceptible to human activity. The authors point out that this preference for a
particular micro-habitat emphasizes the need for conservation despite the fact
most suitable habitat in the Western Ghats, for this species is included in areas
already protected.
Bites
from the Humped-nosed Vipers are also turning out to be a more serious problem
than previously thought. Hypnale
hypnale
and H. nepa can cause renal failure and haemostatic dysfunctions.
Several fatalities due to H. hypnale envenoming, for which there is no
specific antivenom, have been reported in India and Sri Lanka. One reason the
bites are particularly troublesome is that the snakes are frequently
misidentified as Saw-scale Vipers (E. carinatus) in Kerala, India.
Consequently, many H. hypnale bite victims end up receiving ineffective
antivenom (Alirol et al. 2010; Joseph, et al. 2007). Tan et al. (in Press 2010) report clinical studies indicate the
locally available polyvalent antivenoms produced in India are not effective
against Hump-nosed Pit Viper venom. Therefore, there is a need for an effective antivenom. Tan et al. examined the ability of the Malaysian
Pit-Viper, Calloselasma rhodostoma, monovalent antivenom and the Hemato
polyvalent antivenom, both produced by Thai Red Cross Society (TRCS) to
neutralize the lethality and toxic effects of H. hypnale venom. They
chose this antivenom because C. rhodostoma is considered a sister of H.
hypnale. In vitro neutralization studies of Hemato polyvalent
antivenom effectively neutralized the lethality of H. hypnale venom
(1.52 mg venom/ml antivenom), as well as the hemorrhagic, procoagulant and
necrotic activities of the venom. The monovalent C. rhodostoma antivenom
also neutralize the lethality and toxic activities of the venom, but the
potency was lower. Experiments with Hemato
polyvalent antivenom effectively protected mice from the lethal and local
effects of H. hypnale venom. Thus the Hemato polyvalent antivenom may be
beneficial in the antivenom treatment of H. hypnale envenoming.
Literature
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J. K., I. D. Simpson, N. C. Menon, M. P. Jose, and K. J. Kulkarni. 2007. First
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(Hypnale hypnale) in India. Transactions
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N.S., T. D. Jadhav and S. K. Shyama 2010a. Distribution and abundance of pit
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N. S., T. D. Jadhav and S. K. Shyama . 2010b. Habitat suitability, threats and
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Cross neutralization of Hypnale hypnale
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antivenoms in vitro and in a rodent model. Acta
Tropica In Press, Accepted
Manuscript;doi:10.1016/j.actatropica.2010.11.001