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!


The Meal…


The Starter…Creepy Crawlies

Snakebite (DDT) 3

“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)


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


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


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


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


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


http://www.who.int/neglected_diseases/integrated_media_snakebite/en/index.html





No accurate figures A handful of epidemiological studies


In Zimbabwe


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


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


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


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


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)


Elapids - Representative species


The Egyptian Cobra


http://www.kostich.com/black%20mamba.JPG

http://animals.nationalgeographic.com/animals/enlarge/black-mamba_image.html

The Black Mamba




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


The Green Mamba

http://www.africanreptiles-venom.co.za/green_mamba.html


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


Elapids - Clinical Presentation




Black mamba bite Dendroaspis polylepis Ngwelazana, South Africa: showing ptosis, external ophthalmoplegia and facial paralysis recovering on the day after the bite. © Iain Thirsk



http://cache.eb.com/eb/image?id=92719&rendTypeId=4

The Mozambique Spitting Cobra


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


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


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


Vipers - Representative species


http://www.popularpets.net/snakes/pictures/african-puff-adder.php

The African Puff Adder


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


Vipers - Clinical Presentation


http://www.popularpets.net/snakes/pictures/african-puff-adder.php

The African Puff Adder


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


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


Colubrids - Representative species

Toxinological Meal (DDT) 40http://www.africanreptiles-venom.co.za/boomslang.html

http://www.tigerhomes.org/animal/pictures-boomslang.cfm

The Boomslang


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


Colubrids - Clinical Presentation


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


Asps


The Burrowing Asp

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


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


First aid therapy


Immobilisation Technique© David A. Warrell (WHO, 2008)

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)


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


And For Dessert…Mushroom




Hope you had a pleasant meal…heee, heee, heeee, heeeee, heeeeee {Evil laugh!}


May God Bless You All!!!

Snakebite in Zimbabwe: Venomous Snakes and Management

Health & Medicine