Sri Lanka will soon have an anti-venom serum produced locally to treat thousands of snake bite patients.
The Indian Anti venom serum which is available in hospitals at present does not cover for hypnale envenoming.
The first to propose the development of an anti- venom for Hypnale was Dr. Anslem de Silva, better known as Sri Lanka’s father of herpetologists, at the first World Health Organisation (WHO) International seminar on Epidemiology and Medical Treatment of Snake bites, held in Japan, August 1980. Hypnale causes the highest incidence of venomous snake bite in the country but few deaths.
Apart from Dr. de Silva, Professors SAM Kularatne, Kolitha Sellahewa, Ariyarani Ariyaratnam, Kalana Maduwage and Dr. Namal Ratnayake of the teaching hospital in Ratnapura are considered experts in managing hypnale snake bits. Dr. Ratnayake is currently a PhD candidate, studying the Hypnale species.
Two species of hump-nosed vipers (Hypnale hypnale and H. zara) are common even in home gardens, agricultural fields and in coffee and tea plantations etc. Also known as kopi polonga, it is often difficult to spot owing to its cryptic colouring which merges with the undergrowth, resulting in workers being bitten often. Interestingly, local experts now consider Kunakatuwa or Polonthelisa too as deadly species.
This is one reason for the high incidence of hump nose viper bites in the country, however, the mortality rate is two per cent, says Dr. de Silva. While there have been no recorded deaths to date, caused by Green Pit Viper bites, Dr. de Silva stated that studies are ongoing.
Modern medical experts have shown that a victim with serious bites suffers acute kidney injury and many other complications when it involves the Hypnale species.
Of the 105 snakes species found here, more than 50 are endemic to the country. However, this number is expected to change soon.
Of the land snakes only few are medically important or can inflict a bite in which the snake venom could be mild, moderate or highly venomous. It is of interest to note that to date modern medical literature records that human fatalities have been caused by only four species of snakes, namely, Russell’s viper, Cobra, Kraits and the Hump nosed viper.
The Hump-nosed pit viper (Hypnale hypnale, Merrem’s pit viper) is a snake widely found in Sri Lanka and the South Western coastal region of India. It is the commonest snake responsible for venomous snakebite in Sri Lanka, contributing to an estimated 22% to 77% of all snakebites (de Silva, 1981; Seneviratne, 2000). For centuries it was considered to be a relatively innocuous snake. However, in 1821, for the first time, swelling and bleeding due to bites by H. hypnale was reported in animals (Davy, 1821).
Two species of hump-nosed vipers (Hypnale hypnale and H. zara) are common even in home gardens, agricultural fields and in coffee and tea plantations etc. Also known as kopi polonga, it is often difficult to spot owing to its cryptic colouring which merges with the undergrowth, resulting in workers being bitten often.
Of late there has been an increase in the number of Hump nosed vipers, particularly Merrem’s Hump nosed viper bites has increased in the Western Province. It is believed that these reptiles find their way to the Western province with the vegetable, fruits and flower pots that are brought in from rural areas.
The information is corroborated by the National Poison Centre that there have been many Hump nosed viper bite victims in the Western Province. However, it is too early to say whether the actual rate had gone up. Those species thrive on rubber estates.
In Sri Lanka, 97 per cent of the deaths due to snake bites have been caused by the Cobra, Russell’s viper and the Common Indian krait. Apart from the big three, the Sri Lankan krait and Saw scaled viper are also categorized as deadly species though they have not caused many deaths.
It is of interest to note here that traditional literature for the past 1000 years list medicaments for these four snakes, and much less for others, suggesting that our ancestors were aware of the potentially venomous snakes.
The first epidemiological survey of snake bites in the entire island was conducted by Dr. Silva in 1975 and the results published in a prestigious Japanese Journal in 1976. The Pattern of Snakebite in Sri Lanka, the Snake 8(1): 43-51.
He was also one of the first to conduct a detailed study of the snake bite problem in the Anuradhapura district – which was highly praised and reviewed by a world renowned authority on snakebites Prof. David Worrall of Oxford University.
He received an award for his study on Bungarus caeruleus: its ecology and bite in Sri Lanka which was presented at the 10th World Congress on animal, plant and microbial toxins, held at University of Singapore November, 1991.
In early 1980’s the Sri Lanka Medical Association established the Snake bite Expert Committee – and Dr. Silva was a member of the committee since 1983, and actively took part in elevating the hump nose as an medically important snake.
Lowland Hump-nosed Viper Hypnale zara 35cm (Sinhala Mukalan Thelissa)
Description: Body small and stout. Head flat and triangular. Tip of snout distinctly raised compared to snouts of other hump-nosed vipers, and bears large protuberance (larger than that of Millard’s Hump-nosed Viper, Loreal pit between nostril and eye. Body colour dull, and varies from yellowish-brown to dark brown, with two rows of distinct sub oval or sub triangular blotches that meet on dorsal midline. Dark stripe runs across eye to cheek. Belly, much lighter than upper parts.
Distribution: Lowland wet zone at 60–1,000m above sea level. Endemic to Sri Lanka.
Habitat and Habits
Found in primary and secondary forests, and occasionally home gardens. Nocturnal and terrestrial. Occasionally climbs short shrubs and bushes. During day, hides under logs, stones and decaying leaf litter.
When resting, keeps head at 45-degree angle to the ground. Feeds on mice and small reptiles. Ovoviviparous, giving birth to 5–8 young.
Millard’s Hump-nosed Viper Hypnale nepa 30cm (Sinhala Kandukara Mukalan Thelissa)
Description Body small and stout. Head flattened and triangular. Snout pointed upwards with tip that bears small protuberance. Loreal pit between nostril and eye. Body covered with feebly keeled scales. Body colour varies from yellowish-tan to dark brown, with 2 rows of distinct sub oval or subriangular blotches that meet on dorsal midline. Dark stripe runs across eye to cheek. Belly, much lighter than body.
Distribution : Central Highlands at 1,250–1,850m above sea level. Endemic to Sri Lanka.
Habitat and Habits
Occurs in primary and secondary forests, as well as forest edges. Nocturnal and terrestrial.
During day hides under logs, stones and decaying leaf litter. When resting, keeps head at 45-degree angle to the
ground. Feeds on lizards and small snakes. Ovoviviparous, giving birth to 5–8 young. Moderately venomous.
Merrem’s Hump-nosed Viper Hypnale hypnale 40cm (Sinhala Polon Thelissa; Tamil Kopi Viriyan)
Description: Body small and stout. Head flat and triangular, with snout pointed upwards. Loreal pit between nostril and eye. Body dull in colour, varying from light brown, olive or grey, to dark brown with darker scattered lateral spots along it. Neck region lighter, with small spots. Tip of tail lighter. Belly pale, mottled with minute brown or grey spots.
Distribution: Coastal lowlands to 800m above sea level. Common in wet zone. Extra-limital: Western Ghats of India.
Habitat and Habits
Found in home gardens, plantations, grassland and undisturbed forests. Nocturnal and terrestrial, occasionally ascending trees. During day, hides under logs and among leaf litter, which nicely camouflages it. When resting, keeps heads at 45-degree angle to the ground. Feeds on lizards, frogs and mice. Ovoviviparous, giving birth to 3–18 young. Easily agitated and bites viciously when provoked. Highly venomous.