Snakebite in Zimbabwe: Venomous Snakes and Management
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Transcript of Snakebite in Zimbabwe: Venomous Snakes and Management
Toxinological Meal (DDT) 1
A Three Course Toxinological Meal…
By
(Chef) Dr Dexter Tagwireyi BPharm(Hons), MAppSci(Tox), PhD
Senior Lecturer & Toxicologist/PharmacistSchool of Pharmacy, College of Health Sciences
University of Zimbabwe
Menu Menu
Creepy Crawlies for a Starter… Hissy Elongates for the Main Course… Mushy Toxicants for you Desert..
OBJECTIVES OF MEAL◦ To expose participants to important toxinological
delicacies in Zimbabwe [EXPLAIN]
HOPE YOU ENJOY YOUR MEAL….BON APPETITE!
Toxinological Meal (DDT) 2
The Meal…
“But when Paul had gathered a bundle of sticks and laid them on the fire, a viper came out because of the heat, and fastened on his hand…but he shook off the creature into the fire and suffered no harm.” (Acts 28 vs. 3 – 5)
Toxinological Meal (DDT) 4
Now on to the Main Meal…
Dr Dexter TagwireyiBPharm(Hons), MAppSci(Tox) PhD
Senior Lecturer in Toxicology and Drug InformationSchool of Pharmacy
College of Health SciencesUniversity of Zimbabwe
Toxinological Meal (DDT) 5
The Main Meal:Snakes and Snakebite
By the end of this talk, participants should;◦ Have some working knowledge on venomous
snakes in Zimbabwe◦ Have an idea of common signs and symptoms
of snakebite envenomation◦ Have an idea of management and first aid of
snakebite◦ Should not be ‘totally’ lost when someone talks
about venomous snakes in Zimbabwe
Toxinological Meal (DDT) 6
Objectives
Animal envenomation accounts for about a tenth of all admissions to major referral hospitals in Zimbabwe (Tagwireyi, et al., 2002)
Animals involved include◦ snakebite (>80%)◦ scorpion sting◦ spiders and other insects
Toxinological Meal (DDT) 7
Introduction
Over 2500 species of snakes world-wide Only <200 are recorded as being
venomous Australia home to most venomous snake
in the world In Zimbabwe there are about 76 species
of snakes from seven families◦ only between 19 - 22 are thought to be
venomous◦ venomous snakes belong to four families
Toxinological Meal (DDT) 8
Snakebite
Appears to be a “developing” country problem In Britain about 200 hospital admissions annually
due to the common European adder (Vipera berus) (12 deaths by 1993).4
WHO estimates about one million snakebites on the African continent alone ◦ involving 500 000 envenomations with 40% being
hospitalised. Estimated that snakebite causes about 100
deaths per day in India and Pakistan. However, there remains a paucity of reliable data
on the prevalence, incidence, morbidity and mortality of snakebite in developing countries.5,6
Most cases result of agro-based activitiesToxinological Meal (DDT) 9
Snakebite – Some Statistics
“…researchers estimate that 421,000 envenomings and 20,000 deaths occur worldwide from snakebite each year, but warn that these figures may be as high as 1,841,000 envenomings and 94,000 deaths, especially in areas of sub-Saharan Africa and South Asia where antivenoms are hard to obtain. India has the highest estimated annual envenomings and deaths: 81,000, and 11,000 respectively.” http://www.who.int/neglected_diseases/integrated_media_snakebite/en/index.html
Toxinological Meal (DDT) 10
The four families are:◦ Elapids (Elapidae)◦ Vipers (Viperidae)◦ Colubrids (Colubridae)◦ African Burrowing Asps (Actractaspididae)
Bites from venomous colubrids and asps are documented as being rare
Most bites occur from vipers esp. puff adder
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Venomous snake families
These vary from country to country Include;
◦ farming activities◦ time and season◦ occupational activities◦ endemnicity/population◦ types of snakes◦ gender-related activities◦ other
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Factors associated with snakebite
These are varied and include:◦ Snake characterisics
date of last bite or feeding size of snake age of snake (?) type of snake other
◦ Patient characteristics age, sex of victim bite site e.g., foot vs neck nutritional status of patient medical status of patient incl. Drugs other
Toxinological Meal (DDT) 17
Factors affecting severity of bite
These are normally big snakes and include all cobras, mambas, rinkhals
all have large, hollow, non-hinged fangs situated in front of the mouth
Toxinological Meal (DDT) 18
Elapids
Fangs
Figure 21: Eastern Green Mamba Dendroaspis angusticeps © David A. Warrell
Pictures from. WHO (2008), Guidelines for the Prevention and Clinical Management of Snakebite in Africa, WHO Publications, Geneva
Cobras include Egyptian Cobra (Naja haje) Forest Cobra (Naja melanoleuca) Mozambique Spitting Cobra (Naja mossambica)
Mambas include Black mamba (Dendroaspis polylepis) Green mamba (Dendroaspis angusticeps)
Rinkhals (Hemachatus haemachatus) Shield nosed snake (Aspidelaps sculatus)
Toxinological Meal (DDT) 19
Elapids - Representative species
Toxinological Meal (DDT) 21
http://www.kostich.com/black%20mamba.JPG
http://animals.nationalgeographic.com/animals/enlarge/black-mamba_image.html
The Black Mamba
Toxinological Meal (DDT) 22
Picture from. WHO (2008), Guidelines for the Prevention and Clinical Management of Snakebite in Africa, WHO Publications, Geneva
Toxinological Meal (DDT) 23
Picture from. WHO (2008), Guidelines for the Prevention and Clinical Management of Snakebite in Africa, WHO Publications, Geneva
Black Mamba Dendroaspis polylepis Gede, Kenya Kakamega, Kenya © David A. Warrell
Toxinological Meal (DDT) 25
http://cache.eb.com/eb/image?id=92719&rendTypeId=4
The Mozambique Spitting Cobra
Produce large quantities of venom containing potent neurotoxins
Little or no local damage spitting cobras are an exception - extensive tissue
damage venom in eyes leads to severe pain, ulceration of
cornea within 24 hrs and blindness Typical clinical presentation of bites:
dizziness, sweating, muscular weakness and paralysis ptosis, respiratory distress, facial palsy death from respiratory depression
Toxinological Meal (DDT) 26
Elapids - Clinical Presentation
Toxinological Meal (DDT) 27
Picture from. WHO (2008), Guidelines for the Prevention and Clinical Management of Snakebite in Africa, WHO Publications, Geneva
Toxinological Meal (DDT) 28
Black mamba bite Dendroaspis polylepis Ngwelazana, South Africa: showing ptosis, external ophthalmoplegia and facial paralysis recovering on the day after the bite. © Iain Thirsk
Pictures from. WHO (2008), Guidelines for the Prevention and Clinical Management of Snakebite in Africa, WHO Publications, Geneva
Toxinological Meal (DDT) 29
http://cache.eb.com/eb/image?id=92719&rendTypeId=4
The Mozambique Spitting Cobra
Toxinological Meal (DDT) 30
Elapids – Spitting Cobra
Spitting Cobra Naja nigricollis spit Zaria, Nigeria: showing intense conjunctivitis© David A. Warrell
Figure 95: Blindness from dense corneal opacity resulting from untreated Black- Necked Spitting Cobra Naja nigricollis spit 5 years previously © David A. Warrell
Pictures from. WHO (2008), Guidelines for the Prevention and Clinical Management of Snakebite in Africa, WHO Publications, Geneva
Have large hollow fangs in front of mouth Fangs are hinged - move forward in
preparation for a bite Have large heads - ace of spades normally
Toxinological Meal (DDT) 31
Vipers
Puff adder (Bitis arietans)◦ most dangerous snake in Africa, stubborn◦ distributed throughout Zimbabwe
Gaboon adder (Bitis babonica)◦ very large fangs (4 - 5 cm), also inject very
large volume of venom deep into tissue◦ beautiful snake, rarely bites, very big (20 kgs!)
Berg adder (Bitis atropos)◦ weak neurotoxic venom
Toxinological Meal (DDT) 32
Vipers - Representative species
Toxinological Meal (DDT) 33
http://www.popularpets.net/snakes/pictures/african-puff-adder.php
The African Puff Adder
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http://www.africanreptiles-venom.co.za/gaboon_adder.html
The Gaboon Adder/Viper
http://www.lowdown.co.zm/2007/2007-04/kalimba.jpg
http://photos.mg.co.za/citj/photos/0.84051200%201189615352.jpg
Medically important species have cytotoxic venom leading to tissue damage
Typical symptoms include pain and swelling at bite site localised tissue necrosis formation of blood blisters (puff adder) Death results from disseminated intravascular
coagulopathy heamaturia, heamorrhagic oedema (gaboon
viper) Dyspnoea
Toxinological Meal (DDT) 35
Vipers - Clinical Presentation
Toxinological Meal (DDT) 36
http://www.popularpets.net/snakes/pictures/african-puff-adder.php
The African Puff Adder
Toxinological Meal (DDT) 37
Vipers - Clinical Presentation
Untreated Puff Adder Bitis arietans bite Zaria, Nigeria: showing local necrosis at the site of the bite 20 days after the bite. © David A. Warrell
7-year old patient: showing blistering of bitten hand. © David A. Warrell
Pictures from. WHO (2008), Guidelines for the Prevention and Clinical Management of Snakebite in Africa, WHO Publications, Geneva
Very large family of snakes ◦ most non-venomous snakes in this family
Long thin snakes, back fanged Medically important ones have very toxic
venom - chew on victim
Toxinological Meal (DDT)
38
Colubrids
Two medically important colubrids Boomslang (Dispholidus typus) Savannah vine snake (Thelotornis
capensis) both are tree snakes
Toxinological Meal (DDT) 39
Colubrids - Representative species
Toxinological Meal (DDT) 40http://www.africanreptiles-venom.co.za/boomslang.html
http://www.tigerhomes.org/animal/pictures-boomslang.cfm
The Boomslang
Toxinological Meal (DDT) 41
http://www.africanreptiles-venom.co.za/southern_vine_snake.html
The Savannah Twig/Vine Snake
Bites from these snakes are very rare - ‘shy’ venom contains haematoxin
◦ affects blood clotting snake bite victims ‘bleed’ to death
latent period of 1 - 24 hours after bite bleeding from gums, GIT, urinary tract bleeding from old wounds, mucous membranes fang punctures normally exude blood stained serum Progressive intravascular coagulopathy leads to
death
Toxinological Meal (DDT) 42
Colubrids - Clinical Presentation
Toxinological Meal (DDT) 43
Pictures from.by David Warrell WHO (2008), Guidelines for the Prevention and Clinical Management of Snakebite in Africa, WHO Publications, Geneva
All are burrowers, most are harmless Are back fanged - partially hinged with
unusual toxic venoms: cardiotoxins, also cytoxic
Bibron’s burrowing asp (Actractaspis bibronii) only species found in Zim
medium-sized, slow moving, moderately thick snake - widespread in Zimbabwe
Toxinological Meal (DDT) 44
Asps
Bites normally in snake-handlers stabs victim - normally with one fang Symptoms include
immediate (intense) pain local swelling joint stiffness occasionally blistering and necrosis at bite site regional lymphadenopathy no neurological symptoms have been reported,
but may be minor haematological symptoms
Toxinological Meal (DDT) 46
Asp - Clinical Presentation
DO NOT ◦ cut and suck bite site◦ apply ice packs◦ apply torniquet (?)◦ make incisions at site◦ chop off limb
DO◦ calm patient◦ apply torniquet (?)◦ wash site with soap and water◦ apply pressure bandaging with immobilisation (?)◦ rush to hospital
Toxinological Meal (DDT) 47
First aid therapy
ABCs - supportive therapy ATT Antivenin (polyvalent) should be given is
evidence of envenomation look out for anaphylaxis: give adrenaline,
hydrocortisone test dose no longer recommended
Special (monovalent) antivenin for boomslang: flown from South Africa
No antivenin for vine snake Role of antibiotics? (Tagwireyi et al., 2001)
Toxinological Meal (DDT) 49
Management at hospital
Snakebite (DDT) 50
Prevention of Snakebite - Tips Give a snake a chance to “run away”
Most snakes prefer not to confront larger animals Try to know venomous snakes in your area
Stay out of its bite range if you have to chase away Snakes can enter house to hide or for food
Avoid keeping chickens, livestock in house Store food in “rat-proof” containers Avoid sleeping on floor – raise beds above floor Cut all tree branches that are close to or make contact
with your house Keep granary away from houses
Snakebite (DDT) 51
Prevention of Snakebite - Tips Outside the house
◦ Shine a light on you foot path at night◦ Avoid walking barefooted esp. in bushy areas◦ Where gum-boots when working in snake areas◦ Keep grass short, clear rubbish, etc.,◦ Avoid handling ‘dead’ snakes with bare hands◦ Avoid trying to run over snakes with car◦ Be careful where you step or sit◦ Heavy rains ‘move’ snakes to roadsides
Toxinological Meal (DDT) 55
Hope you had a pleasant meal…heee, heee, heeee, heeeee, heeeeee {Evil laugh!}