ENVENOMATION Flashcards
Snakebite envonoming is a …… disease
Neglected tropical disease
Snakebite envenomation is a ————- medical emergency
Life threatening
Which regions of the world experience snakebites the most
Tropical and Subtropical
Vast majority of deaths due to snakebites occur in ………
Sub Saharan Africa and south east Asia
Country with the highest snakebite mortality
India
Why do children suffer more severe effects from snakebites than adults
Due to their smaller body mass
Why do children suffer more severe effects from snakebites than adults
Due to their smaller body mass
Epidemiology of snakebites
Males are bitten more than females
Agricultural workers and children are most affected
Elderly are at a greater risk of mortality
Number of snake species considered venomous
600 out of the 3500 species
Classification of snakes to their suborder
Class Reptilian
Order Squamata
Suborder Serpentes
Venomous snakes are in ——- families
Five
Largest and second largest venomous snake families
Viperidae and Elapidae
Five families of venomous snakes
Colubridae
Atractaspididae
Elapidae
Viperdae- Viperinae
Crotalidae
Examples of Colubridae
Boomslang
Bird snake
Examples of atractaspididae
Burrowing asps
Examples of elapidae
Cobras, kraits, coral snakes , mambas, death adder, tiger snake, most Australian snakes
Examples of Hydrophiidae
Hydrophiidae are in the family Elapidae
Examples are Sea snakes and Sea kraits
Examples of Viperinae ( True/Pitless vipers)
Vipers
Adders
Asps
Examples of Crotalidae or pit vipers
Rattlesnakes
Bushmaster
Copperhead
Types of snake fangs
fangless (aglyphous),
rear-fanged (opisthoglyphous),
front fanged and fixed maxilla (proteroglyphous),
Front fanged and mobile maxilla (solenoglyphous)
Anatomical classifications of snakes based on fangs
Colubridae- Opisthoglyphous
Elapidae- Proteroglyphous
Viperidae- Solenoglyphous
Atractaspididae- All types of fangs
Which family of snakes contain species capable of spraying their venom
Elapidae
Two examples of cobras
Common cobra- Naja naja
King cobra- Ophiophagus hannah
Examples of kraits
Common krait: Bangarus caeruleus
Banded krait: Bangarus fasciatus
Most venomous snake based on the murine LD50
Western or Inland taipan from the family Elapidae
Examples of true cobras (Najas)
Common cobra - Naja naja
Black necked spitting cobra- Naja nigricollis
Egyptian cobra- Naja heje
Key identification feature of the common cobra
Well marked hood
Monocellate or Binocellate spectacle mark
Key identification feature of the common krait
Paired white bands
Two examples of mambas
Green mamba - Dendroaspis angusticeps
Black mamba - Dendroaspis polyplepis
Features of pit vipers
Pit between eye and nostril
Flat triangular shaped head
Vertical pupils
Curved fangs
Examples of true or pitless vipers
Russell’s Viper - Daboia russelii
African saw scaled viper or carpet viper - Echis ocellatus
African puff adder - Bitis arietans
Examples of pit vipers /Crotalidae
Rattlesnakes
Cottonmouth or Water moccasin
Copperhead
Bushmaster
Key identification feature of the Russell’s viper
Black edged almond or chain shaped marks on the back
Examples of rattlesnakes
Sidewinder
Diamondback
Key venomous snakes in Ghana
West African saw scaled / carpet viper - Echis ocellatus
Puff adders- Bitis arietans
Black necked spitting cobra- Naja nigricolis
Senegales cobra - Naja senegalensis
Western green mamba -Dendroaspis viridis
Identification features of venous and nonvenomous snakes
Venomous
Triangular head or arrowhead head
Elliptical pupil
Fangs
Single row of subcaudal anal plates
Harmless
Oval head or egg shaped head
Round pupil
Double row of subcaudal anal plates
Difference between poison and venom
Venom must be injected into the body by mechanical means however poisons must be ingested inhaled or absorbed
Venoms are generally nontoxic if swallowed
Functions of snake venom
Prey immobilization
Assist in or start the digestive process
Self defense
Causes of difference in snake venom composition
Geographical distribution
Seasons of the year
Age or ontogenic variation
Two main classes of snake venoms
Proteins and Peptides
Non enzyme and Enzymes
Non proteinaceous components
Effect of 3FTX neurotoxin
Selective inhibition of nAchR
Effect of 3FTX cardiotoxin
Membrane perturbation by electrostatic and hydrophobic interactions with the cell membranes
Effect of Disintegrin peptide components
Inhibit platelet aggregation
.
Effect of kurnitz type inhibitors
Inhibition of serine proteases (e.g., plasmin, kallikrein, trypsin).
Interferes with the blood coagulation cascade and fibrinolysis
Effect of natriuretic peptide components
Vasodilation
Hypotension
Increase NO production
Cardiprotective action
Effect of BPP( Bradykinin potentiating peptides) protein components
Inhibit the function of ACE and raise the level of bradykinin.
Hypotension
Effects of Crotamine peptide components
Interacts electrostatically with DNA.
Penetrates membranes via heparan sulphate proteoglycans binding.
Effects of safarotoxin
Vasoconstriction via endothelin receptors
Effect of waglerin
nAChR antagonist.
Effect of CRISPs
Inhibit high K induced contraction
Effects of PLA2
Hypotension
Vasorelaxation
Antiatgetogenic activity
Effects of 3FTXs
Hopotension
Vasorelaxation
Inhibition of platelet aggregation
Effect of fibrinolytic enzymes
Inhibit platelet aggregation
Fibrinolytic activity
Which snakes produce neurotoxic venoms
Elapidae- cobras, kraits, coral snake
Hydrophiidae
Small Bitis vipers
Russell’s viper
Which snakes produce cytotoxic venoms
Black necked spitting cobra
Bothrops asper
Saw scaled/ Carpet viper
Snakes that produce haemotoxic venoms
Viperidae, spitting cobra, certain Colubridae
Snakes that produce myotoxic venoms
Hydrophiidae
Snakes that can produce venoms with combined toxicities
Spitting cobra
Saw scaled or carpet viper
Signs of neurotoxic venoms
Descending muscular paralysis
Predominant neurotoxic toxins
PLA2
3FTX
Sign of cytotoxic venoms
Swelling at the bite site which can develop into blistering and bruising and hypovolaemic shock
Predominant cytotoxic toxins
Hydrolytic enzymes eg: Snake Venom Metalloproteinases (SVMPs)
PLA2s
Non enzymatic cytotoxic 3FTs
Signs of myotoxic envenoming
Negligible local swelling
Myalgia
Associated features of neurotoxic venoms and progressive descending paralysis
Rhabdonyolysis and renal failure