1. Poisonous snakes and
envenomation in
Sri Lanka
Dr. Devika Iddawela
Department of Parasitology
Faculty of Medicine
Peradeniya.
Y2S2 – 09/10 batch

2. Objectives
to be able to-
 State how snakes are classified into poisonous and non-
poisonous
 Name the poisonous snakes found in Sri Lanka
 Name the common non-poisonous snakes in Sri Lanka
 Recognize these if shown a specimen/image
(to be achieved in the demonstration)
 State the major effects of snake venom in the different
groups of poisonous snakes in Sri Lanka
 State the principles underlying the treatment and
management of snake bites
 State how snake bites can be prevented.

3. SNAKES
Free living organisms
Limbless, scaly, reptiles
Medically important as
bites of some cause systemic poisoning

4. Medically important snakes of Sri Lanka
Snakes are elongate, limbless
reptiles with bodies covered in
scales
Sea snakes
13 species in
Sri Lanka
Land snakes
83 species in
Sri Lanka

5. SNAKE FAUNA OF SRI LANKA
 SEA SNAKES
 LAND SNAKES
-Elapids
-Viperids
-Colubrids- ground, burrowing,
arboreal,aquatic
- Earth snakes (primitive)
- Wart snakes (aquatic)
- Constrictors (crush prey)

6. POISONOUS OR VENOMOUS SNAKES
Cephalic gland (below & behind the eye)
secretes venom (poison) which is ejected
through a specialised tooth- the FANG

7. grooved canalized
Elapids,vipers &
Sea snakes have
Venom glandsFang

8. short, fixed-
elapid

10. Some colubrids have small venom
gland located posterior with posterior
fangs
-Duvenoy’s gland

11. Depending on venom toxicity to humans,
snakes are grouped as
 HIGHLY (DEADLY) venomous
 MODERATELY venomous
 MILDLY venomous

12. WHO , 2010
Medically important snakes : two
categories
Category 1 – Highest medical importance
Highly venomous snakes which are
common or widespread, cause numerous
snake bites
Resulting high level of morbidity and
mortality

13. Include: Common Krait,
Ceylon cobra, Russell’s viper
Hump nosed viper( Hypanale
hypanale)
Category 2: secondary medical importance
Highly venomous snakes capable of causing
morbidity, disability and death BUT for which
exact clinical and epidemiological data are
lacking or less frequently implicated because
of their behaviour or habitat preferences

14. Include:
Elapidae:Ceylon krait
Viperidae: Saw scaled viper,
Green pit viper,
Hypananale nepa
Hypanale walli

15. Identification of Poisonous Snakes
of Sri Lanka: on their habitat
 SEA SNAKES
 LAND SNAKES

16. SEA SNAKES
13 species in the Indian ocean
cases of poisoning reported in SL
most common sp. Palamis
Features: flat, rudder –like tail
laterally compressed
tail
body

17. SCALATION- arrangement of scales
Head scales if enlarged are called SHEILDS
costals
sub caudals
Important in identification
vertebrals
ventrals

18. Scalation important in
differentiating venomous from non
venomous
• head scales,
• ventrals,
• vertebrals and
• subcaudals

19. kraits
• The head scales and vertebrals
are enlarged.
• The subcaudals are single and
NOT divided
vipers (except in hump nosed viper)
head scales are small and equal in
size.

20. Body form and shape: Of the
poisonous snakes elapids and
vipers can be differentiated on
the shape and form
Elapids Vipers
Form:slender Thick&stout
Tail: Long Short
Head: spatula shaped Triangular
Neck Not distinct Distinct

21. ELAPIDS
characteristics:
Slender body; long tail; head spatula
shaped; no distinct neck
Scalation: head scales enlarged
Vertebrals enlarged, sub caudals single
 Ceylon Cobra
 Kraits- Common krait, Ceylon krait
 Ceylon Coral snake

22. CEYLON COBRA
Naja naja naja
Only snake in with a hood (loose fold
of skin behind head)
Hood has characteristic markings
dorsal
‘spectacle’
variations seen
ventral
2 dark spots

23. common around human habitations
largest elapid in SL average length 1200 m
slow moving, usually not aggressive
unless
provoked. If provoked assumes
characteristic postureyoung cobras very aggressive
and equally poisonous
colour varies

24. Defense posture: raises forebody
(usually 1/3) remains 5-10 min
with hood expanded and hiss
strikes with raised part of the body
cobras are shy, run and hide
when people are around.

25. Many snake charmers remove the fangs or the
venom sacs from their snakes, because it is too
dangerous. This practice is illegal, and is
considered inhumane to the snake.

26. CEYLON KRAIT
Bangarus ceylanicus
single bands all round belly
Kraits- dark banded snakes
Nocturnal
Found in low country
wet zone
Fully grown adult –
2-3 feet

27. COMMON KRAIT -Indian krait
Bangarus caeruleus
narrow double bands, clear belly
active at night and relatively
passive during the day.

28. Kraits- distribution
Common krait : dry & intermediate zones
Ceylon krait : Wet & parts of intermediate zone
Enters houses, usually in the night, found hiding
under furniture,mats etc.
Human bites caused due to accidental
crushing/trampling
little or no pain at the site of a
krait bite

29. contain neurotoxic venom
that is 16 times more potent
than cobra venom
extremely powerful and
quickly induces muscle
paralysis

30. Ceylon Coral Snake
(slender coral snake)
small snake , highly poisonous
but rare,
Habitat: under fallen leaves,logs
bites not reported in Sri Lanka

31. VIPERS
 TRUE VIPERS
 PIT VIPERS- loreal pit (thermoreceptor)
between eye & nostril
Short tail; stout body
Head- triangular, distinct neck
Head scales usually not enlarged
viviparous
It is sensitive to IR (Infrared)
radiation, thus allows the snake to
locate warm-blooded prey.

32. LOREAL PIT

33. Vipers
True vipers Pit vipers
Based on the presence or absence of a loreal pit, one on
Each side of the head between the nostril and the eye
TV
Russell’s viper
Saw-scaled viper
PV
Green pit viper
Hump-nosed viper

34. TRUE VIPERS
Russell’s viper- Vipera russelli pulchella
Body: 3 rows of oval, chain-like markings
Head-inverted ’V’ mark
;s;a fmd<.d odrfmd<.d

36. widely distributed
in all climatic zones
thick snake average
length of 900 mm
sluggish, nocturnal
Attacks readily in defense
hisses loudly, strikes
from a coiled position,
hurling whole body

37. Saw scaled viper- Echis carinatus
Bird’s foot or dagger marking on head
Scales saw- like edge
Habitat: under sand, coastal areas
Grating noise due to scales rubbing
against each other
Smallest viper –200 mm
Active, very aggressive
Confined to Jaffna
peninsula

38. PIT VIPERS
GREEN PIT VIPER
m<d fm<.d
arboreal, common in highland areas
medium/large snake, 750- 1300 mm

39. Stout snake
arboreal,nocturnal
sluggish
well camouflaged
with the surroundings
Grouped as highly
Venomous

40. HUMP NOSED VIPER
common, Viperine head with enlarged head
Scales,snout acutely
pointed & upturned- 300 mm
Hypnale hypnale; H h nepa
l+klgQjd" fmdf<dka f;,siaid
Human bites from this
snake is common and
fatal bites have been
reported in Sri Lanka.

41. COLUBRIDS
 Non poisonous-majority
 Mildly poisonous
(11 species)
Duvernoy’s gland & rear,grooved fangs
vertebrals NOT enlarged,
sub caudals -biserial (twinned)
comprise the majority of snakes
Arboreal,aquatic,land, burrowing

42. Posterior fanged colubrids (Mildly
poisonous)
Aquatic- water snakes
diyabariya
Arboreal (8 spp.)-
whip (vine) snakes
cat snakes
blossom snake
flying snake Polmal karawala

43. CAT SNAKE (Mapila )
Pupil slit vertical, head triangular shape
mildly poisonous, several colour variations
no human fatalities caused
Wrongly identified as
a hump nosed viper
but can be
differentiated by the
absence of a loreal pit
and humped snout

44. Polmal karawala- flying snake
tree snake
Common in dry zone, can glide, back -fanged
WATER SNAKE- dog-faced water snake
osh nßhd

45. Whip (Vine) SNAKE
Pupil transverse,
long slender
Common green, brown colour variation
Arboreal, aggressive, vicious biter

46. Non-venomous colubrids
Majority of snakes in Sri Lanka
eg. common kukri snake
many diurnal, active, small snakes
frequents houses, hides
under masonry
light-dark brown with black
markings

47. Flying snake

48. RAT SNAKE
Long slender, dorsal
olive green/brown dark edged scales
.erähd
very common, enters houses, in search of prey
feed on rats

49. CEYLON WOLF SNAKES
WOLF SNAKES
very common, banded snakes
mistaken for kraits
Ceylon wolf snake single banding
as in Ceylon krait but vertebrals
NOT enlarged

50. EARTH SNAKES
Lives underground, harmless, very small
blind snakes
WART SNAKES
Water, rough skin
eg. Pipe snake
-depath kaluwa
Diya goya

51. CONSTRICTORS
Kills pray by coiling around
pray and constricting
Python, Sand boa
Quadrate markings on body
msUQrd" je,s msUQrd

52. Poison (venom)
composition complex
MYOTOXIN-myalgia, myoglobinuria
NEUROTOXIN- ptosis, dysarthria,alteration in
level of conciousness, respiratory failure
VASCULOTOXIN- non clotting of blood
haemotytic, haemorrhagic
intravascular thrombosis

53. Sea snakes: neurotoxin+ myotoxin
necrosis of muscle Loss of myoglobin
muscle enzymes
potassium
myalgia, myoglobinuria
Kraits: post synaptic + pre synaptic toxin
minimal local reaction,muscle paralysis
mortality high
Cobra:Post synaptic neuro toxins;local reaction+
muscle paralysis

54. Enzymes:
Russell’s viper venom- proteases
activate mammalian blood clotting cascade
Hyaluronidases- spread of venom in tissue
Proteolytic enzymes- local changes in vascular
permeability oedema, blisters, necrosis
Sri lankan russell’s viper: both
vascular and neuro toxins

55. Systemic effects
Early effects –specific symptoms & signs
vary with the type of snake
Viper bites – blood stained sputum,
ecchymoses,bleeding from gums and bite
wound, prolonged clotting time, ptosis,
dysphagia, external ophthalmoplegia,
dysarthria
Elapid bites -ptosis, dysphagia, dysarthria,
mental confusion, respiratory failure
Sea snake bites – myalgia
myoglobinuria, respiratory failure

56. Severe envenomation – rapid death after
elapid bites
Most protracted after viper bites
Management
Trivial envenoming – Aches, stiffness, pain
in limbs , neck
• No treatment needed.
• In doubt – admit, observe
Serious envenoming –
• Respiratory failure
• Electrolyte disturbances –hypokalaemia
• Renal failure

57. Management contd.
Start tetanus prophylaxis & antibiotics
(cloxacillin)
Monitor:
• Pulse rate
• Blood pressure
• Respiratory rate
• Temperature
• Urine output
• Fluid balance

58. FIRST AID
 Treat shock & fright, reassure
 Wash wound with soap and water/clean cloth
to prevent/limit entry of pathogens
 Immobilise as for fracture (if limb)
to minimize dissemination (spread) of poison
 Remove rings, bangles etc. on bitten limb
to minimize tissue damage that could arise from effects of
envenomation
 Paracetamol for pain no alcohol,aspirin, narcotic drugs
or nasal instillations
 Transport patient to hospital
? Venous tourniquet if available.

59. Transport victim to the nearest
hospital
• Send killed snake to hospital for
identification
• avoid - alcohol, aspirin, incision,
suction, cauterization
do not panic. It is better to do
nothing than to do harm

60. Specific antisera
Polyvalent antivenin
(VINS Bioproducts Ltd. India in current use)
Not effective against
sea snakes/ hump nosed viper
Sea snake antivenin-Commonwealth
Serum Laboratories, Australia
Supportive therapy:
Tetanus toxoid,antibiotics
renal./respiratory failure

61. PREVENTION
 use bright light in the dark
 use foot wear
 look where you tread& warn
them by treading heavily as
snakes are relatively deaf but are
Sensitive to ground vibration
Snakes bite only in defense
when & if provoked.

62. Do not handle or keep snakes
unless you are an expert
Snakes are cold blooded and an
apparently dead snake may well be
alive. Reflex biting can occur

63. Do not put your hand into
ant hills, cavities in trees
and thick under growth and
under logs
Keep your dwelling free of
rats, mice, frogs, lizards
which attract snakes

64. Information on snake bites: incidence
morbidity, case fatality not very accurate
Only 30-40% seek hospital care
Based on few hospital based studies confined to
geographical areas.
Very important health problem in Sri Lanka
2002- 37,200 treated at government
hospitals
Hambantota District 10th
leading cause of
hospitalization

65. Over 80 land snakes in Sri Lanka only
6 are known to cause fatalities.
Only ½ snake bites are by deadly
poisonous snakes and only ¼ of these
cause systemic poisoning
Russell’s viper-30%
Cobra 17%
Kraits 15%
Recent studies: Hump nosed viper bites 27%
of the snake bites and 2% fatality reported

66. Take home massage
Not All snakes bite
Not all snake bites are
venamous
Not all venamous snake
bites are fatal