ReviewArticle
oi M crobiologyand mmunology
Sherman A. Minton, Department
nd ana Un versitySchoo of Medicine
nd anapo s lndiana46223
PoisonousSnakesand Snakebitein the U.S.:
A Brief Review
Abstract
T h i s a r t i c l eb r i e f l y . e v i e w ss o m cc u r r c n t i d c a sr e g B r d i n gs n a k e t r i t ien t h e U n i l e d S t a t e sT
. w e n t ys p e c i e so f n a r i v ev € n o n o u s
s n a l e so c c u r a n d i n c l u d e l 5 s p e c i e so f r a t t l e s n a k e st h, e c o p p e r h e a da n d c o t o n m o u r b ,r w o s p e c i e so f c o r a l s n a k c sa, n d o n e
s e a s n a k eS. n a k ev e n o m s . o n t a i na v a r i e t yo f e n z y m e sa n d n o n - e n z y m a t itco x i n s .C o m p o s i t i o nm a y v a r y g e o g r a p h i c a l j yo,n ,
togenetically,and indiridually. As dererminedby nouse loxicity, nost lethal venons are thoseofrhe Mohaveraltlesnske(Crotalus
s.ltrlatrs), tiger ratlesnake (C. t;grn), and pelagic seasnake(Peldn;s pldrrrz.r). Venonous snales mey bite {irhour injecring
venom and rarely inject more than half their available venom. Some colubr;d snakesgenerallr presumednonrenomous,such
a s g a r t e r s n a k e sc, a n i n r a r e i n s t a n c e si n f l i c t y c n o m o u sb i ! c s .
M o s t s n a k e b i t eisn t h e U n i t e dS t a t e sa r e s u s t a i n e d
c l o s ct o t h e v i c l i m ' sh o m ea n d u s u a l l yr e a c hm e d i c a a
l i d w i t h i na n h o u r .
Fishermen,hunters, and l,ackpackersdo nol seen lo be a high risk group. Almost half the biles result fron delibcrate conlact
with a venonous snale. Srmptoms of pit viper envenomationa.e.eviewed. A persistentdrop ;n blood pressureis rhe single
m o s t r e l i a b l ei . d i c a t ; o . o f d a n g e r o u se n y e n o m a t i o nA. b o u t h a l f t h e c o r a l s n a k eb i l e s d o n o l r e s u hi n e n v e n o m a t i o nb,u t i t
i s s e r i o u sw h e n i t o c c u r s .
Snakebitefirst aid neasures and principles of t.eatmenl are reyie$ed. Two relatively ncw procedures,elastic bandaging
of s bitten Iimb and use of a powerful small suction derice are discussed.Proceduresunder developnent include ELISA tests
to improve diagnosisand eyaluatc therBpy,anlivenomsof higher polency and lower allergenicity,and imnunizadon for hieh
risk indiriduah. Becauseof the complexily of evaluaiing snakebireand the chancethat a laynan might altempr a naiye treatrnent more harmful lhan helpful, the enphasis in first aid for snak€bit€is to get the stri.ken individual pronptly to a hospiral.
lntaoduction
The Snakesand Their Venoms
Although venomoussnakebitesare uncommon ln
the United States (6000.7000casesannually), they
generate a disporportionate amount of interest,
anxiety, and controversy. There are several
r e a s o n sf o r t h i s . F i r s t , s n a l , e b i t ei " a s i t u a t i o n
where a complex organism (a snake) injects a
complex secretion(venom)into another complex
organism (a human). This generates a staggering number of variables and allows for outcomes
thal can range from death in less than an hour
to a totally trivial injury. Second, the composi
l i o n a n d a m o u n l o f v e n o ma s n a k ei n j e c t sv a r i e .
with geographic locality, season, and the age,
size, and health of the reptile. Third, there are
no good animal models (aside from monkeys) for
evaluating the action of snake venoms on man
and the effectivenessof treatments. The mouse
is widely used, but it is not a very small human
being. Finally, the unpredictable course of snakebite and the limited knowledge that most physi'
cians have of venomous snakes and their bites
may cause uncritical acceptance of treatment
plans.
Thereare 20 speciesof unquestionably
venomous
snakesknownfrom the United States-15 species
of rattlesnakes,
the copperheadand cottonrnouth,
two other pit vipersthat are closelyrelatedto
eachother,and two speciesof coralsnakes.The
(Pelamisplaturuslis ocr"asionpelagicseasnake
ally reportedin Hawaiianwatersand has been
recordedonceon the coastof extremesouthern
California.Additionallythere are severalsnake
speciesthat are essentially
harmlessbut can,on
rare occasions,
inflict a mildly venomousbite.
Rattlesnakes
occur in at least 45 of the contiguousstatesand four Canadianprovinces,althoughthey are usuallyquite local in distribution, and their numbershavebeengreatlyreduced
in the last half century.Speciesthat presentthe
greatestdanger to man are the easternand
(Crotalusad,amanteus
westerndiamondbacks
ar,d
C otro.t),timber rattlesnake(C horridusl,prairie
rattlesnake(Co. oiridis), northern and southern
Pacific rattlesnakes (C.r:. oreganus and C.t.
helleri), aladMohaverattlesnake(C. scutulatus).
The pigmy rattlesnake (Sislrurus miliarius)
causesmany bites in the southernstates,but
t30
NorthwestScience,Vol. 61, No. 2, 1987
fatalitiesare unknown.The other species(see
T a b l el ) , ' i t h e ra r eu n c o m m oonr o c c u ri n r e g i o n s
wherethey havelittle contactwith man.The copperhead(Agkistrodorxcontortr;x), with a wide
rangein the easternUnitedStatesand abilityto
survivein well populatedareas,probablycauses
more bitesthan any one speciesof rattlesnake,
but fatalitiesare virtuallyunknown.The cottonmo[th (A. piscioorus)has a more lirnited range
and prefers swampsand sluggishwaterways.
it accountsfor a significantnumber
Nevertheless
of snakebitesin the southeasternstatesand
fatalitiesare on record.Coralsnakesare highly
. he eastern
"peci""
s e c r e t i t ea n d s e l d o ms c e n T
(Micrurus fuhius), which may reach 1.2 m in
length,is potentiallylethal;the smallerArizona
species (Micruroid.es eurytanthus) has never
causeda human fatality.
TABLE 1. \'enomous snakesof the United States and Canada and their geographic distribution
Distribution
Scientific Name
comnon NameG)
Crotolus adananteus
E a s t € r nD i a m o n d b a c kR a t l t e s n a k e Coastal plain, from se. Nonh Carolina to Lounrana
Western Diamondback Rattlesnake Weslern Arkansas& s. Oklahoma thru mosl of Texas to
se. California'
Southern Arizona & s. California deserts'
Sidewinder
'linber
New England to .. Florida, sesl to central Texas, norlh
Rattlesnake
to se. Nebraska,s. Wisconsin & s€. Minnesola
C a n e b r a k eR a t t l e s n a k e
( s o u r h e r np o p u l a t ; o n s )
Mountains and canyonsfrom s. central Texas lo se.
RockRattlesnake
Speckled Rattlesnake
Pananint Rattlesnak€
Western Arizona, s€. Utah, !. Ne'ada, s. California-
B l a c k t a i lR a t t l e s n a k e
South central Texas lo w. Arizona'
M o u n t a i n so f s e . A r i z o n a '
Tsin-spotted Rattlesnake
South1{este.nCali{ornia'
Trans-PecosTexas to s. Nevada & adjacent Cali{ornia.
Red Dianond Rattlesnake
Crota[usvutulatus
Mohave Rattlesnak€
Crotalus tigris
Tiger Rattlesnake
S o u t h c e n t r a lA r i z o n a '
Vest Texas and New Mexico norlh to {. North Dakota,
t lbetta'
M o n t a n a ,s e . S a s k a t c h e w a&n a d j a c e n A
Most of Cslifornia north ro s. centrnl Bfitisb Colunbia'
Prairie Rattlesnake
Pac;f;c Rattlesnake
Crotalus t. tutosus
Creat Basin Rattlesnake
Sistturus catenLtus
R i d g e - n o s eR
d atllesnake
M a s s a s a u gR
aaltlesnake
N e v a d a ,w . U t a h & o r e g o n ,s . I d a h o . '
Mountains o{ s€. Arizona & adjacent New Mexico.
Southern Onrrrio, i{. New York & nw. Pennsylvania
southsest to se. Arizona & s. Texas"
Eastern Norlh Carolina to e. Texas & Oll:rhoma, s.
Missouri, sv. Kentuck)
Sourhern Ne* Engiand to Florida penhandle, we* ro
Trans'PecosTexas, north to se. Nebraska,cenlral Indiana
Plgny Rattlesnake
Agkistrodon contontir
Copperhead
& 0hio
SoutheasternVirginia to cenrral Texas rnostly at low
elevations,north to cenlral Missouri & sw. Indiana
Coasial plain from se. North Carolina to sN. Texas, north
ABkistro.Ionpiscirotus
Water Moccasin
Micruroides curyxanthus
CoralSnake
A r i z o n ao r S o n o r aC o t a l S n a k e
Pelagic Sca Snake
Y e l l o wb e l l i e ds e a s n a k e
S o u r h e r nA r i , o n a & s w . N e w M e x i c o "
Hawaii, extreme sr. California coast. Fe{ rccords, prob
a b l y b a s e do n s t r a l s . '
' S p e c i e sa l s o o c c u r si n M e x i c o .
.'Orher subspeciesof C/ordlus,l/td;s occur in parts ofArizona, Urah, Coloradoand Wvoning. Theseare Ct. cozcolor(Midget
Faded Rattlesnake),C.. nunli&s (Hopi Ra lesnake),Cr. cerDerus(Arizona Black Rartlesnake),and er. c6yszs {Grand Canyon Rattlesnake).
PoisonousSnakesand Snakebitein the U.S.
l3l
Snakevenomsare the mostcomplexof animal
toxins,containingup to twentyor so biologically
active proteins and polypeptides.Many are enzymes.Thosethat are most important and wide(enspreadincludephospholipase
A and proteases
dopeptidases)
that accountfor someof the hemorrhagic and necrotizing activity, arginine ester
hydrolases
that contributeto hypotensive
and anticoagulant activity, and hyaluronidasethat
facilitatesthe spreadof venom in tissues.There
are also non-enzymaticmyotoxinsand neurotoxins.It mustbe emphasized,
however,that the effects of snake envenomationresult from many
venomcomponentsacting in concert.The classificationofvenomsasneurotoxic,hemorrhagic,or
m y o l o r i ci s u s u a l l )a n o r e r s i m p J i f i c a t i o n .
As judgedby mousetoxicity,the mostlethal
rattlesnakevenomis that of the tiger rattlesnake
(Crotalustigrts)lollowedby that of the Brazilian
rattlesnake(C. durissus terrificus), Mohave rattlesnake,and midget fadedrattlesnake(C. t iridis
concolor). All these venomscontain a powerful
neurotoxin.In SouthAmericanrattlesnakes,
it
is knownas crotoxin;in North Americanrattlesnakesas Mohavetoxin. Recentwork showsthe
two are immunologicallyvery similar (Weinstein
et al, l9B5\, Mouse lethal dosesfor some rattlesnakeand other snakevenornsare shownin
Table2. Venomsof manysnakespeciesshowind i v i d u a lo. n t o g e n i ca.n dg e o g r a p h irca r i a t i o ni n
lethality and other prope ies. Venomsof two
gravid tirnberrattlesnakescollectedthe sameday
on the samehilltop showeda five-folddifference
in lethaltoxicity(Minton 1953).In at leastthree
rattlesnake
species,
venomsof youngsnakesdiffer markedlyfrom thoseof adultsin protein composition(Minton1967,Fieroet al. 1972,Minton
& Weinstein1986).In all, lethality seemsto peak
in snakes6-9monthsof age,then declineto adult
levels.Reportsof unexpectedly
severereactions
to bites of young rattlesnakesindicate this variation may be of clinical significance(Reid &
Theakstonl97B).Overa largepart of its Arizona
range,venomof the Mohaverattlesnake
doesnot
containMohavetoxin and is much like venon
of the western diamondbackrattlesnakein
l e t h a l i tayn dp r o t e o l y tai cn dh e m o r r h a gai cc t i v i t y
(Glenn el rrt 1983). Venom from western
diamondback
rattlesnakes
from westTexasand
Arizonahasgreaterlethalitybut lowerproteolytic
activitythan that of snakesfrom north Texasand
Oklahoma(Minton & Weinstein1986).
132
Minton
T A B L E 2 . V e n o m) i e l d s i . o m a d u l t s n a k e so t a r e r a g es i z e
and mouselethaldoscs.B.rsedchieflyon daralrom
tbe aothor'slaborrtor_y
and from Clenn & Straight
(1982).
Species
CrctaLusadamanteus
Crotalus atot INE)
Crctalus atrc, (SW)
Crotalus cerates
Crctatus horridus
Croralus tepi.d.us
CrotaLusnitcheLli
Crotalus nolossus
Crctalus pr;.cei
Crotalus ruber
Crotalus s<:utulatus
Crotalus tigri
Crotalus t riridis
Crotalus L helleti
Crotalut t. concolor
Crotalus uillard.i
Sisturus catenatus
Sistrutus nilidrius
contortrit
piscircrus
Micrurus fuh,ius
euqxanthus
Pelamisplaturus
Averase Mouse LD/50 mgrkg
Venom Yield
intra
sub'
(md
renous cutaneous
250-500
200,400
100250
30-60
100-200
5-30
75-150
150-300
2l2
200-400
40-100
5'15
50-100
75-150
10-25
2-15
15-40
7.25
40-70
100150
4-16
0.5 3
0.25'l
1.68
3.15
2.O7
2.25
2.63
0.95
3.72
0.16
0.06
l.61
1.29
0.28
L6l
0.25
3.65
14.55
t9.52
14.16
12.35
9.15
I1.55'
r0.90,
t6.42
I t.39
21.25
0.31r
0.21
16.15
3.56
5.25.
24.25
t0.92
25.60
5.1t
0.38
25.80
r.30
0.90
0.705
'Based on specimensfrom the Big Bend resion of Terias.
Eyidenceindicatesmuch variation in loxicit) anone populations o{ this species.
lBased on specimensfron San Diego Co., Caiifornia. A
subspecies{ith much nore toric renom occu6 in Baja
California.
rBasedon specinensfrom populationsshos€ v€nomcontains
Mohale toxifl.
'Based on Indiana specinens.Venon ofwesternpopularions
a p p e a r st o b e l e s st o x i c .
sBasedon specirnensfron the Coral Sea.
Who GetsBittenand Why
Thosewhosework or recreationtakesthem
outdoorsand into remoteareasoften consider
themselvesat specialrisk from snakebite.Unless
their activitiesincludehuntingsnakes,
thisis not
the case.Snakebitethroughoutthe world is
largely a matter of contacthours.The snakethat
b i t e s1 o u i s m o s tl i k e l yo n e l h a t l i v e si n y o u r
gardenor underyour house.Most snakebites
in
the UnitedStates,unlessthey involvedeliberate
contactwith venomoussnakes,occur within a
half-mileof the vicrim'shome.Writing of his ex'
in California,Russell(1980p.
tensiveexperience
2 6 9 ) . u 1 " " g o n , . r r y l o p o p u l a ro p i n i o n .m o s l
in the United Statesoccur within a
snakebites
shortdistancefrom medicalcare.In California,
l f t h e r a t t l e s n a kbei l e so c c u r
orpr g0 perceno
within city limits or within 2 milesof city limits
in foothill area.., Felr bites occur in
backpackers,
serioushunters,or fishermen. . . In
the past 20 years, there has been only one
backpackerin the Sierras of California, who I
knowof, who has beenbitten by a rattlesnake,
d h e nh e r n a sc h a n g i n ga t i r e
a n d t h i sh a p p e n ew
at the end of his hike."
Until about 1950,most snakebitesin the
with what could
United Stateswere associated
broadlybe calledagriculturalactivities.When
I wasgrowingup in southernIndiana,the first
snakebiteof the seasonmight occurwith mushroom hunting in late April but was more likely
with strawberryor blackberry
to be associated
picking in late May or June.Other bitesweresustainedwhilelifting rocks,clearingweedsor rubbish,or doing other choresaboutthe farm. Todaythere are many fewersmallfarmswheremost
of the work is doneby hand,and therehasbeen
a great increasein large scale mechanized
agriculture.0n the other hand, there has also
beena decidedincreasein permanentor seasonal
rural living. Rural children ages5-12havealways
beena comparativelyhigh risk group if rhey live
where venomoussnakesare relatively plentiful.
Children of this age are more likely to go
barefootand be lessthan carefulwherethey step
or where they put their hands. Many small
childrenare insatiablycuriousaboutsnakesand
today are more likely to try to catchreptilestheir
grandparents
at the sameagewouldhavekilled
forthright.Todaya much higherpercentageof
bites involvedeliberatecontactwith venomous
snakes.
Snakecatching,snakehandling,and the
keepingof venomoussnakesin captivityattract
p e o p l ew h o s em o t i v e sv a r y f r o m s e r i o u "s c i e n .
tific interestto exhibitionismand religiousfervor. With a few,abuseof alcoholand drugsmay
contributeto the risk.
The Bite and lts Effects
An important fact not always appreciated by
physicians or laymen is that venomous snakes,
includingthe most dangerousspecies,may inject little or no venomwhenthey bite. According
to one study, only about half the bites by the
A s i a nc o b r ar e s u l li n p o i s o n i n g
nidell-feared
(Reid 1964).In 16 of 3l coral snakebitesin the
(Neill
southeastern
U.S.,no poisoningdeveloped
cop1957,Parrish& Khan 196?).Rattlesnakes,
perheads,
appearto be more
and cottonmouths
efficientbiters with about 75 percentof bites
resulting in envenomation.Experirnentsin laboratoriesin severalparts of the world agreethat
snakesrarelyinject more than half their available
venomin a singlebite. There is somesuggestion
that a defensivebite directed againsta predator
or an animal too large to seNe as food results
in lessvenom injection than a bire intended to
kill prey. However,rattlesnakesattacking prey
may alsodeliverrelativelyineffectivestrikes(Kardong l986). The degreeto which snakescontrol
t h e a m o u n lo f v e n o mi n j e c t e di n v a r i o u s i l u a unknown.
tions remainsessentially
When a rattlesnakeor other pit viper delivers
an effectivebite, pain is usually immediateand
intense,although occasionally,and usually with
a very severebite, theremay be numbnessaround
the areaof the bite lastingaslong as 30 minutes.
Puncture wounds are obvious and bleed longer
and more freely than a nonvenomousltound.
Swellingusuallybeginswithin a few minutesand
spreadsboth peripherallyand centrally. Discoloration around the bite usually is evidentwithin
a few minutes.If pain, swelling,and discoloration
are absenl 15-30minutes after a pit viper bite,
the odds are very good no venom was injected.
Important exceptionsare individuals bitten by
rattlesnakeswhosevenomsare low in those toxins that are responsiblefor local swelling and
discoloration.This includessomepopulationsof
rock
speckledrattlesnake,
the Mohaverattlesnake,
rattlesnake,and tiger rattlesnake.Swelling and
discolorationmay alsobe minimal in the rare instancewhen most of the venomis injected intravenously.However,the individual who sustains
such a bite quickly showssigns of generalized
poisoning,and the diagnosisof envenomationis
rarely in doubt. Individuals under the influence
of alcohol or drugs may not have normal pain
perceptionand may displaybizarre symptoms.A
usuallyseenwithin
reliablesign of envenomation,
the first hour after a bite, is painful swellingof
lymph nodesin the groin if the bite is on the foot
or leg and in the axilla if on the hand or arm.
PoisonousSnakesand Snakebitein the U.S.
133
Tingling of the face and metallic taste in the
mouth are commonsymptomsof rattlesnakebite.
Nausea,
vomiting,chills,sweating,
andrhirstare
commonsymptomsof pit viper biteswithin the
first hour. Hemorrhagicblebsmay appearwithin
two hoursafter a bite or be delayedmuch longer.
Thesesymptomsdefinitelyindicatepoisoningbut
not necessarily
a seriousor life-threatening
bite.
A persistentfall in blood pressureis probably
t h em o s tr e l i a b l e
i n d i r " a t i oonf a s c r i o u p" i t v i p e r
bite. This may manifestitself as faintnessor loss
of consciousness
with pallor and a weak,rapid
pulse. Other ominous signs are generalized
musculartwitching,videspreadappearance
of
large hives(angioneuroticedema),diarrhea,contractedpupils,and sensation
ofyellowvision.All
may developwithin an hour after the individual
is bitten.
Coralsnakebitesare not very painful;there
is little or no swellingand no discoloration.Fang
puncturesbleedlittle and may be almostundetectablea few hours after the bite. Characteristicallythere is an asymptomaticperiod that can
last up to sevenhours.In fact, in abouthalf the
cases,no definitesignsof poisoningeverdevelop.
Not many casesof coral snakebiteshave been
reportedin detail,but symptomsseemto be quite
variable.Sometimes,
there are pains radiating
from the locationof the bite or in the abdomen.
Seriousmanifestations
includedroopingof the
eyelids, difficulty in speaking and swallowing,
generalized
muscularweakness
and incoordinalion, drowsiness,
and difficulty in breathing.This
can progressto a completeand fatal paralysis.
A curiousand not well understoodphenomenon is thal of venomousbites by presumably
nonvenomous
snakesof the family Colubridae.
Somecolubridshaveenlarged,groovedfangsin
the rear of the upperjaw, and at leasttwo African
speciesare unequivocallydangerous.A few
s p e c i e sw i l h t h i s t y p e \ e n o m a p p a r a t u sj u s t
enter the United States along the Mexican
border,and a few casesof mild venomousbites
by them havebeenreported.The most serious
casesreportedin the United Stateshaveresulted
from bites of Asian snakessuch as the yamakagashi (Rhabdophis tigrinus) and red-necked
keelback(R. subminiatus\pvchased as rnnocuous pets (Mittleman & Goris 1974, Cable et al.
l9B4).Thesesnakeshaveenlargedbut ungrooved
teeth in the rear of the upper jaw. Poisoningby
thesesnakesresultsin a dramaticdecreasern cer134
Minton
tain blood clotting factors with resultant internal
and external hemorrhages and related complications. Rhabd,ophis is closely related to the North
American garter snakes (Thamnophis\ ard water
snakes(flerodla), so it is not surprising that a few
cases of envenomationscharacterized by pain,
swelling, and ecchymosis have been reported
following bites of garter snakes.Two plentiful
and r,videlydistributed species, the wandering
garter snake (7. elegans ,a€,.o/rs) and common
garter snake (7. sirtalis\ have been implicated.
Similar cases have been reported following bites
by hognose snakes (Heterodon). However,
perhaps only one in several thousand bites by
thesepresunably nonvenomouscolubrids results
in poisoning. The answer may be in the nature
of the colubrid venom apparatus. Duvernoy's
gland, roughly the equivalent of the pit viper
v e n o m g l a n d .h a s a h i g h l y t o x i c s e c r e l i o ni n a l
least some colubrid snakes.But it has a very small
lumen for venom storage. And a solid tooth is
not so effective for introducing venom into a
wound as one that is grooved or hollow. When
a colubrid snake feeds,it often holds and chews
its prey. This gives time for Duvernoy's gland
to secrete venom which is worked into wounds
made by the teeth. It probably is significant that
a majority of human envenomations by colubrids
involve snakesthat hung on for severalseconds.
And in some cases,a captive snake bit when being offered food.
FirstAid and DefinitiveTreatment
Statedsimply,the objectivesof snakebitetreat,
ment are:(l) Removevenombeforeit can combine with targettissues.(2)Neutralizevenomthat
cannot be removed.(3) Counteracteffectsof
(4) When all
venomthat cannotbe neutralized.
the abovefail, repair the damage.
Snakebite
treatmentin the UnitedStateshas
seen a number of colorful and downright
dangerous
procedures
advocated,
sometimes
by
scientists
and physicians.
In southern[ndianain
the 1920's and 30's, whiskeywas a popular
remedylnearlyeveryfarmerkepta bottleor two
"just in case." Other popular
treatmentswere
applicationof the split body of a freshly-killed
chickento the bite or soakingthe bitten pan in
keroseneor turpentine.First aid techniquesinvolvingligature,incision,and suctionhavebeen
widelyadvocated
and are soundin principlebut
of dubiousvaluein practice.Ligaturesincrease
pain andhavelittle effectin rctardingspreadof
venom. Incision followed by suction does
facilitateremovalof somevenom.However,innenes,
cisionsmay damagelargebloodvessels,
or tendons,provideentry for infection,and be
follovedby seriousbloodlossparticularlysince
many snake venoms markedly impair blood
coagulation.Excision-cutting out the entire
areaarounda bite-is almostcertainto do more
harm than good and cannotbe recommended.
Chillingthe areaarounda bite by useof ice or
chemicalspraywith or withouta ligatureis ineffective and can do seriousdamageif continued
for a prolongedperiod.Recently,electricshock
using high voltage,low amperagecurrent from
an outboardmotor, lawn mower'or othet source
hasbeensuggestedasfirst aid for snakebite.The
methodis underinvestigationbut cannotcurentIy be advocated.
As alreadymentioned,most personsbitten by
snakescan reach definitive medical care within
30-50minutes.Realizingthis, I havemaintained
for the last decadeor so that the most useful
snakebitefirst aid kit consistsof car keys and
somecoinsfor a call to a hospital.If at all pos'
sible,the actualdriving to the hospitalshould
else.The stressof drivbe entrustedto someone
ing in traffic doesnot help a snakebiteand vice
versa.Callingaheadis important.It givesthe
emergencyroom time to pfeparefor the patient's
arrival,and the physicianon duty can consull
with colleaguesor call a Poison Information
Centerif he wishes.The snakeshouldbe brought
to the hospitalwith the victim if possibleso its
identitycanbe verified.It is betterif the reptile
is dead.A live snakein a hospitalemergency
r o o mi s a n c p d l e sdsi s t r a . t i o na n d s o m e l i m eas
importantif
hazard.Identificationis especially
for harmlessmimics
a coralsnakeis suspected,
ofcoralsnakesoccurin manypartsof the United
States.In casesof bitesby exoticsnakeskept as
p e t s .i d e n l i f i c a t i oonf t h e r e p t i l ei s v " r y i m p o r '
tant also.
seemto be efTwo relativelynewprocedures
fectiveand safe enoughthat their use can be
cautiouslyadvocatedfor the small number of
such
that occurundercircumstances
snakebites
that a delayof 30 minutesor more in reaching
a medicalfacilitycan be anticipated.0ne is the
useof elasticbandagessuchas are widelyused
to treat sprainsw.appedsnuglyoverthe areaof
the bite and extendedup the bitten limb to the
trunk if thereis enoughbandage.I am told that
substitute.The
panty hosemake an acceptable
limb is then immobilizedwith a splint.The bandagesare left in placeuntil the victirnreaches
int h e h o s p i t aal n d p r e p a r a t i o nf os r b e g i n n i n g
travenousadministrationof antivenomhavebeen
made.Both experimentaland clinicalevidence
indicate the technique is quite effective in
preventingabsorptionof venomfrom a bitten
limb (Sutherland 1983, pp. 22'32).The rnethod
in Australiawherethe important
wasdeveloped
snakeshavevenomsthat are highly lethal but not
very destructivelocally.If usedfor treating bites
by rattlesnakesand other pit vipers whose
venomscausesignificantlocal damage,it must
poisonbe with the realizationthat generalized
i n g m a y b e p r e v e n t eadl l h e c o s lo f i n c r e a s i n g
local darnage.It is the recomrnendedprocedure
for bites by coral snakeswhosevenomsare more
like thoseof Australiansnakes.
Another new technique is use of a trlocharnberedsuction devicethat producesone atmospherenegativepressure.This is appliedto
the bite as quicklyas possible@itlro&,making
any incisions and left in place about three
minutes.Suctioncan be repeatedas necessary.
Preliminary animal experimentsindicate up to
half an injecteddoseof rattlesnakevenomcan
be removed.The devicewasalsotestedon three
personsbitten during a rattlesnakeroundupin
the Southwestwith apparentlygood results
(Bronsteine, oL l9B5).SawyerProductsof Long
Beach,California,marketsthe devicein a small,
light, durable kit suitable for field use.
Scientific evaluationof theseand other first
throughdevelophasbeenpossible
aid measures
ment of very sensitiveand specificenzymeJinked
immunoassay(ELISA) for snake venoms.Af
thoughthesetestsare not generallyavailablein
the United States,enoughexperimentalwork has
been done to demonstratetheir value both in
diagnosisof snakebiteand evaluationof treat'
ment. Sincethe test can be done in about two
hours,determiningpresenceof venomin blood
and urine can be helpful in distinguishinga
relativelyminor bite from a potentiallyserious
havealsocontributedto bet'
one.Theseassays
of snake
the pathophysiology
ter understanding
ic
cnvenomation
ohserration
O.n e i n l e r e s t i n g
that venomsof somesnakescan be detectedat
the site of a bite after severaldays.
PoisonousSnakesand Snakebitein the U.S.
135
Althoughit is not the purposeof this review
to discusshospital managementof snakebite,
somethingshouldbe saidaboutantivenom.This
is the only clinically effectiveantidote for snake
venompoisoningand is producedcommercially
by hyperinmunizationof horses with snake
venoms.The product commonlyused in the
United Statesis madeagainstvenomsof three
speciesof rattlesnakes
and a large neotropical
pit viper of the genus Bothrops. lt is at least
somewhateffectivein neutralizingvenomsof all
North American pit vipers and the most important neotropicalspeciesaswell asthoseof a few
O l d W o r l d r i p e r s .A c o r a ls n a k ea n t i v e n o mi s
availablein limited quantity in thosestaieswhere
coral snakesoccur.Antivenomsare by no means
ideal therapeutic agents. Their neutralizing
capacityis relativelylow, hencelarge doses-400
ml or more-sometimesmust be givenin a very
severeenvenomation.Not all venOmsand venom
fractions are equally well neutralized. Antivenomshave little effect against the factors in
pit viper venomsthat causelocal swellingand
necrosis.Being foreign proteins,antivenoms
commonlycauseserumsickness,lessfrequently
anaphylaxis
and otherformsof immunologicinjury. Significantimprovementin antivenomscan
be anricipated.Experimentalantivenomprepared by affinity chromatographyhasmuch better neutralizingcapacityand is lesslikely to cause
(Russellet al, 1985).A commercial
anaphylaxis
product could be availablein a relatively short
time. Monoclonalantibodieshavebeenproduced
against several snake venom toxins, but their
therapeuticuse has not been explored.
Exceptin most unusualsituations,antivenom
shouldbe givenin a hospital.This is but one of
numerousreasonswhy hospitalization
ls recommendedfor all but obviouslytrivial snakebites.
Blood pressureand other vital signsare more
easilymonitored,and hypovolemicshock,the
commonest
causeof deathin pit viper bites,can
be detectedearlyand corrected,0ther dangerous
complicationsof snakebitesuchascoagulopathy,
renal failure, respiratory failure, and infection
can alsobe detectedearly and dealt with more
effectively,In a seriesof 9 fatal rattlesnakebites
in Arizona, two individuals refusedto go to the
hospitaland three othersreachedthe hospital
after delaysof 1.5 to 29 hours(Hardy 1986).
Literature Cited
Clenn, J. L., R. C. Straighi, M. C. Wolfe, and D. L. Ha.dy.
B r o n s t e i nA
, . C . , F . E . R u s s e l lJ, . B . S u l l i r a n ,N . B . E g e n ,
a n dB . R . R u m a c \ .1 q 8 5N
. e g a r i r ep r e * u r p . u . r i n n
in field lrealneni of rattlesnakebite. Vet. Hun. Tox
icol. 28:297,185.
Cable, D., W. McCehee,W. A. Wingert, and F. E. Russell.
1984. Prolonged defibrination after a bite fron a
lnale. JAMA 251:925-926.
Fiero, M. K., M. W. Seifert,T. J. Weaver, and C. A. Bonilla.
1972.Conparative study ofjuvenile and adult prairie
rattlesnake(Croralrs li'idrr !,r.d6) venoms.Toxicon
10:81-82.
C t e n n ,J . L . a n d R . C . S r r a i g h t .1 9 8 2 .T h e r a t t l e s n a k easn d
their venon yi€ld and lethal toricity. 1l[ Tu, A. T.
(ed.) RattlesnakeVenons: their Actions and Trearm e n t . N e w Y o r k . M a r c e l D e k k e r .P p . 3 1 1 9 .
136
Minton
A singlenonfatalsnakebiteconfersno effecl i v ei m m u n i l l .a n de r i d e n r eo f i m muni t y i n p r o fessionaland religious snakehandlerswho have
survivedmany bitesis equivocal.Somehavedied
of snakebite
aftersurvivinglen or moreprevious
bites.Immunizationwith toxoid,a strategyhighly
successfulin infections such as diptheria and
tetanus, has been attempted with detoxified
snakevenoms.The only large scaletrial, in the
Ryukyu Islands,was not particularly successful
(Sawaiet al- 1969),but the procedureis being
consideredin someother regionsof very high
snakebiteincidence.In the United Statesit would
be appropriateonly for a very small number of
individuals.The bestsinglepreventativemeasure
is to avoid deliberatecontactwith veromous
snakes."Illegitimate" snakebites,those sustained by individualswho knowinglyplacethemselvesat risk, make up roughly half the snakebites reportedin the United States.
1983.Geographicalvariariot in Crotdlus scututatus
(Mojave rattlesnake) venom properties. Toxicon
2l:119-130.
Hardy, D. L. 1986.Fslal rattlcsnakeenvenonationin Arizona.
J. Tox. Clin. Tox. 24:l 10.
Kardong, K. V. 1986.Th€ predatorystrike ofthe rauiesnale:
when thinss so amiss. Copeia 1986:816-820.
Minron, S. A. 1953.Variation in venom samplesfron copp e r h e a d s a n d t i m b e r r a t l l e s n a k e s .C o p e i a
t9531212-2].5.
t96?. Observationson tonicity and anligenic
makeup of venons of juvenile snakes.1N Russell,
F. E. and P. R. Saundere(eds.)Animal Toxins 0xf o r d . P e r g a m o nP r e s s .P p . 2 1 1 2 2 2 .