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ReviewArticle

ShermanA. Minton, Departmentoi M crobiologyand mmunology nd ana Un versitySchoo of Medicine nd anapo s lndiana46223

PoisonousSnakes and Snakebitein the U.S.: A Brief Review

Abstract

This articlebriefly .eviewssomc currcnt idcas regBrding snaketrite in the Uniled States.Twenty species of narivev€nonous snalesoccur and includel5 speciesof ,the copperheadand cotonmourb,rwo speciesof coralsnakcs, and one seasnake. .ontain a varietyof enzymesand non-enzymatictoxins. Composition may vary geographicaljy,on, togenetically,and indiridually. As dererminedby nouse loxicity, nost lethal venons are thoseofrhe Mohaveraltlesnske ( s.ltrlatrs), tiger ratlesnake (C. t;grn), and pelagic seasnake(Peldn;s pldrrrz.r). Venonous snales mey bite {irhour injecring and rarely inject more than half their available venom. Some colubr;d snakesgenerallr presumednonrenomous, such as gartersnakes, can in rare instancesinflict ycnomousbi!cs. Mostsnakebites in the UnitedStates are sustained closc to theviclim's home and usually reach medical aid withinan hour. Fishermen,hunters, and l,ackpackersdo nol seen lo be a high risk group. Almost half the biles result fron delibcrateconlact with a venonous snale. Srmptoms of envenomationa.e.eviewed. A persistentdrop ;n blood pressureis rhe single mostreliable i.dicat;o. of dangerousenyenomation. About half the coralsnake biles do nol resuhin ,but it is seriouswhen it occurs. 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.Procedures under developnent include ELISA tests to improve diagnosisand eyaluatc therBpy,anlivenoms of 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 treat- rnent 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 TheirVenoms Although venomoussnakebites are uncommon ln Thereare 20 speciesof unquestionablyvenomous the United States(6000.7000 cases annually), they snakesknown from the United States-15 species generatea disporportionate amount of interest, of rattlesnakes,the copperheadand cottonrnouth, anxiety, and controversy. There are several two other pit vipersthat are closelyrelated to reasonsfor this. First, snal,ebitei" a situation eachother, and two speciesof coralsnakes. The (Pelamis where a complex organism (a snake) injects a pelagicseasnake platuruslis ocr"asion- complex secretion(venom) into another complex ally reportedin Hawaiianwaters and hasbeen organism (a human). This generates a stagger- recordedonce on the coastof extremesouthern ing number of variables and allows for outcomes California.Additionally there are several snake speciesthat areessentially harmless but can,on thal can range from death in less than an hour rare occasions,inflict a mildly venomousbite. to a totally trivial . Second, the composi Rattlesnakesoccur in at least 45 of the con- and amounlof venoma snakeinjects varie. tiguousstates and four Canadianprovinces, al- with geographic locality, season,and the age, thoughthey are usuallyquite localin distribu- size, and health of the . Third, there are tion, and their numbershave been greatly reduced (aside no good animal models from monkeys) for in the lasthalf century.Species that presentthe evaluating the action of snake venoms on man greatestdanger to man are the easternand and the effectivenessof treatments.The mouse westerndiamondbacks (Crotalus ad,amanteus ar,d is widely used,but it is not a very small human C otro.t),timber (C horridusl,prairie being. Finally, the unpredictable course of snake- rattlesnake(Co. oiridis), northern and southern bite and the limited knowledge that most physi' Pacific rattlesnakes (C.r:. oreganus and C.t. cians have of venomous snakesand their bites helleri), aladMohave rattlesnake (C. scutulatus). may cause uncritical acceptance of treatment The pigmy rattlesnake (Sislrurus miliarius) plans. causesmany bites in the southernstates, but

t30 NorthwestScience, Vol. 61, No. 2, 1987 fatalitiesare unknown.The other species(see and prefers swampsand sluggishwaterways. Tablel),'ither are uncommon or occurin regions Neverthelessit accountsfor a significantnumber wherethey havelittle contactwith man.The cop- of snakebitesin the southeasternstates and perhead(Agkistrodorx contortr;x), with a wide fatalitiesare on record.Coral are highly rangein the easternUnited States and ability to secretiteand seldom scen. The eastern"peci"" survivein wellpopulated areas, probably causes (Micrurus fuhius), which may reach 1.2 m in morebites than any one speciesof rattlesnake, length,is potentiallylethal; the smallerArizona but fatalitiesare virtually unknown. The cotton- species (Micruroid.es eurytanthus) has never mo[th (A. piscioorus)has a more lirnited range causeda human fatality.

TABLE 1. \'enomous snakesof the United States and Canada and their geographicdistribution

Scientific Name comnon NameG) Distribution

Crotolus adananteus East€rnDiamondback Ratltesnake Coastal plain, from se. Nonh Carolina to Lounrana Western Diamondback Rattlesnake Weslern Arkansas& s. Oklahoma thru mosl of Texas to se. California' Sidewinder Southern Arizona & s. California deserts' 'linber Rattlesnake New England to .. Florida, sesl to central Texas, norlh CanebrakeRattlesnake to se. Nebraska,s. Wisconsin & s€. Minnesola (sourhernpopulat;ons) RockRattlesnake Mountains and canyonsfrom s. central Texas lo se.

Speckled Rattlesnake Western Arizona, s€. Utah, !. Ne'ada, s. California- Pananint Rattlesnak€ BlacktailRattlesnake South central Texas lo w. Arizona' Tsin-spotted Rattlesnake Mountainsof se.Arizona' Red Dianond Rattlesnake South1{este.nCali{ornia' Crota[usvutulatus Mohave Rattlesnak€ Trans-PecosTexas to s. Nevada & adjacent Cali{ornia. Crotalus tigris Tiger Rattlesnake Southcentral Arizona' Prairie Rattlesnake Vest Texas and New Mexico norlh to {. North Dakota, Montana,se. Saskatchewan& adjacentAlbetta' Pac;f;c Rattlesnake Most of Cslifornia north ro s. centrnl Bfitisb Colunbia'

Crotalus t. tutosus Creat Basin Rattlesnake Nevada,w. Utah & oregon,s. Idaho.' Ridge-nosedRatllesnake Mountains o{ s€. Arizona & adjacent New Mexico. Sistturus catenLtus MassasaugaRaltlesnake Southern Onrrrio, i{. New York & nw. Pennsylvania southsest to se. Arizona & s. Texas" Plgny Rattlesnake Eastern Norlh Carolina to e. Texas & Oll:rhoma, s. Missouri, sv. Kentuck) Agkistrodon contontir Copperhead Sourhern Ne* Engiand to Florida penhandle,we* ro Trans'PecosTexas, north to se. Nebraska,cenlral Indiana & 0hio ABkistro.Ionpiscirotus SoutheasternVirginia to cenrral Texas rnostlyat low Water Moccasin elevations,north to cenlral Missouri & sw. Indiana Coasial plain from se. North Carolina to sN. Texas, north Micruroides cu ryxanthus Arizonaor SonoraCotal Snake SourhernAri,ona & sw.New Mexico" Pelagic Sca Snake Hawaii, extreme sr. California coast. Fe{ rccords, prob Yellowbellied ably basedon strals.'

'Speciesalso occurs in Mexico. .'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 Can- yon Rattlesnake).

PoisonousSnakes and Snakebitein the U.S. l3l Snakevenoms are the mostcomplex of animal TABLE 2. Venom)ields i.om adultsnakes ot areragesize ,containing up to twentyor so biologically and mouselethaldoscs. B.rsed chiefly on daralrom active and polypeptides.Many are en- tbe aothor'slaborrtor_y and from Clenn & Straight (1982). zymes.Those that are most important and wide- spreadinclude phospholipase proteases(en- A and Averase Mouse LD/50 mgrkg dopeptidases)that accountfor someof the hemor- Species Venom Yield intra sub' rhagic and necrotizing activity, arginine ester (md renous cutaneous hydrolasesthat contributeto hypotensiveand anti- coagulant activity, and hyaluronidasethat CrctaLusadamanteus 250-500 1.68 14.55 Crotalus atot INE) 200,400 3.15 t9.52 facilitatesthe spreadof venom in tissues.There Crctalus atrc, (SW) 100250 2.O7 14.16 are also non-enzymaticmyotoxins and neurotox- Crotalus cerates 30-60 2.25 12.35 ins.It mustbe emphasized,however, that the ef- Crctatus horridus 100-200 2.63 9.15 fects of snake envenomationresult from many Croralus tepi.d.us 5-30 I1.55' venomcomponents acting in concert.The classi- CrotaLusnitcheLli 75-150 r0.90, ficationofvenoms as neurotoxic, hemorrhagic, or Crotalus nolossus 150-300 t6.42 myoloricis usuall)an orersimpJification. Crctalus pr;.cei 2l2 0.95 I t.39 Crotalus ruber 200-400 3.72 21.25 Asjudged by mousetoxicity, the mostlethal Crotalus s<:utulatus 40-100 0.16 0.31r rattlesnakevenom is that of the tiger rattlesnake Crotalus tigri 5'15 0.06 0.21 Crotalus t riridis 50-100 l.61 16.15 (Crotalus tigrts)lollowed by that of the Brazilian Crotalus L helleti 75-150 1.29 3.56 rattlesnake(C. durissusterrificus), Mohave rat- Crotalut t. concolor 10-25 0.28 tlesnake,and midget fadedrattlesnake (C. t iridis Crotalus uillard.i 2-15 L6l concolor). All these venomscontain a powerful Sisturus catenatus 15-40 0.25 5.25. .In SouthAmerican rattlesnakes, it Sistrutus nilidrius 7.25 3.65 24.25 is knownas crotoxin;in North Americanrattle- contortrit 40-70 t0.92 25.60 snakesas Mohave . Recent work showsthe two are immunologicallyvery similar (Weinstein piscircrus 100150 5.1t 25.80 et al, l9B5\, Mouse lethal dosesfor some rat- Micrurus fuh,ius 4-16 0.38 r.30 tlesnakeand other snakevenorns are shownin euqxanthus 0.5 3 0.90 Table2. Venomsof manysnake species show in- Pelamisplaturus 0.25'l 0.705 dividual.ontogenic. and geographic rariation in lethalityand other prope ies. Venomsof two 'Based on specimensfrom the Big Bend resion of Terias. gravidtirnber rattlesnakes collected the sameday Eyidenceindicates much variation in loxicit) anone popula- on the samehilltop showeda five-folddifference tions o{ this species. lBased in lethaltoxicity (Minton 1953). In at leastthree on specimensfron San Diego Co., Caiifornia. A rattlesnakespecies, venoms of youngsnakes dif- subspecies{ith much nore toric renom occu6 in Baja California. fer markedlyfrom thoseof adultsin com- rBased (Minton on specinensfrom populationsshos€ v€nomcontains position 1967,Fieroet al. 1972,Minton Mohale toxifl. & Weinstein1986). In all, lethality seemsto peak 'Based on Indiana specinens.Venon ofwesternpopularions in snakes6-9 months of age,then declineto adult appearsto be lesstoxic. levels.Reports of unexpectedlysevere reactions sBasedon specirnensfron the Coral Sea. to bites of youngrattlesnakes indicate this varia- tion may be of clinical significance(Reid & Who GetsBitten and Why Theakstonl97B). Over a largepart of its Arizona range,venom of the Mohaverattlesnake does not Thosewhose work or recreationtakes them containMohave toxin and is much like venon outdoorsand into remoteareas often consider of the western diamondbackrattlesnake in themselvesat specialrisk from snakebite.Unless lethalityand proteolytic and hemorrhagic activity their activitiesinclude hunting snakes, this is not (Glenn el rrt 1983). Venom from western the case.Snakebite throughout the world is diamondbackrattlesnakes from westTexas and largely a matter of contacthours. The snakethat Arizonahas greater lethality but lowerproteolytic bites1ou is mostlikely one lhat livesin your activitythan that of snakesfrom north Texasand gardenor underyour house.Most snakebites in Oklahoma(Minton & Weinstein1986). the UnitedStates, unless they involve deliberate

132 Minton contactwith venomoussnakes, occur within a includingthe most dangerousspecies, may in- half-mileof thevicrim's home. Writing of his ex' ject little or no venomwhen they bite. According tensiveexperience in California,Russell (1980 p. to one study, only about half the bites by the 269).u1" "gon,.rry lo popularopinion. mosl nidell-fearedAsian resull in snakebitesin the United Statesoccur within a (Reid1964). In 16 of 3l coralsnake bites in the shortdistance from medicalcare. In California, southeasternU.S., no poisoningdeveloped (Neill orpr g0 percenlof the rattlesnakebiles occur 1957,Parrish & Khan 196?).Rattlesnakes, cop- within city limits or within 2 milesof city limits perheads,and cottonmouthsappear to be more in foothill area.., Felr bites occur in efficientbiters with about 75 percentof bites backpackers,serious hunters, or fishermen. . . In resulting in envenomation.Experirnents in lab- the past 20 years,there has been only one oratoriesin severalparts of the world agreethat backpackerin the Sierras of California, who I snakesrarely inject more than half their available knowof, who hasbeen bitten by a rattlesnake, venomin a singlebite. There is somesuggestion andthis happened when he rnaschanging a tire that a defensivebite directed againsta predator at the end of his hike." or an animal too large to seNe as food results in lessvenom than a bire intended to Until about 1950,most snakebitesin the kill prey. However,rattlesnakes attacking prey United Stateswere associated with what could may alsodeliver relatively ineffective strikes (Kar- broadlybe calledagricultural activities. When dong l986). The degreeto which snakescontrol I wasgrowing up in southernIndiana, the first the amounlof venominjected in varioussilua- snakebiteof the seasonmight occurwith mush- tions remainsessentially unknown. room hunting in late April but was more likely other pit viper delivers to be associatedwith strawberryor blackberry When a rattlesnakeor an effectivebite, pain is usually immediateand picking in late May or June.Other biteswere sus- and usually with tainedwhile lifting rocks,clearing weeds or rub- intense,although occasionally, severebite, there may be numbnessaround bish,or doingother chores about the farm. To- a very bite lastingas long as 30 minutes. daythere aremany fewer small farms where most the areaof the Puncturewounds are obviousand bleed longer of thework is doneby hand,and therehas been and more freely than a nonvenomousltound. a great increasein large scale mechanized usuallybegins within a few minutesand .0n the other hand, there has also Swelling peripherallyand centrally. Discol- beena decidedincrease in permanentor seasonal spreadsboth oration around the bite usually is evidentwithin rural living. Rural children ages5-12 have always few minutes.If pain,swelling, and discoloration beena comparativelyhigh risk group if rhey live a are absenl 15-30minutes after a pit viper bite, wherevenomous snakes are relatively plentiful. the odds are very good no venom was injected. Children of this age are more likely to go Important exceptionsare individuals bitten by barefootand be lessthan carefulwhere they step rattlesnakeswhose venoms are low in thosetox- or where they put their hands. Many small ins that are responsiblefor local swelling and childrenare insatiably curious about snakes and discoloration.This includessome populations of todayare more likely to try to catchreptiles their the Mohaverattlesnake, speckled rattlesnake, rock grandparentsat the sameage would have killed rattlesnake,and tiger rattlesnake.Swelling and forthright.Today a much higherpercentage of discolorationmay alsobe minimal in the rare in- bitesinvolve deliberate contact with venomous stancewhen most of the venomis injectedintra- snakes.Snake catching, snake handling, and the venously.However, the individual who sustains keepingof venomoussnakes in captivityattract such a bite quickly showssigns of generalized peoplewhose motives vary from seriou" scien. poisoning,and the diagnosisof envenomationis tific interestto exhibitionismand religiousfer- rarely in doubt. Individualsunder the influence vor. With a few,abuse of alcoholand drugs may of or drugs may not have normal pain contributeto the risk. perceptionand may displaybizarre symptoms.A sign of envenomation,usually seen within The Bite and lts Effects reliable the first hour after a bite, is painful swellingof An important fact not always appreciated by lymph nodesin the groin if the bite is on the foot physicians or laymen is that venomous snakes, or leg and in the axilla if on the hand or arm.

PoisonousSnakes and Snakebitein the U.S. 133 Tingling of the face and metallictaste in the tain blood clotting factors with resultant internal mouth are commonsymptoms of rattlesnakebite. and external hemorrhages and related complica- ,, chills, sweating, and rhirst are tions. Rhabd,ophis is closely related to the North commonsymptoms of pit viper biteswithin the American garter snakes (Thamnophis\ ard water first hour. Hemorrhagicblebs may appearwithin snakes(flerodla), so it is not surprising that a few two hoursafter a bite or be delayedmuch longer. casesof envenomationscharacterized by pain, Thesesymptoms definitely indicate poisoning but swelling, and ecchymosishave been reported not necessarilya serious or life-threateningbite. following bites of garter snakes.Two plentiful A persistentfall in bloodpressure is probably and r,videlydistributed species,the wandering themost reliable indir"ation of a scriou"pit viper garter snake (7. elegans ,a€,.o/rs) and common bite. This may manifestitself as faintnessor loss garter snake (7. sirtalis\ have been implicated. of consciousnesswith pallor and a weak,rapid Similar caseshave been reported following bites pulse. Other ominous signs are generalized by hognose snakes (Heterodon). However, musculartwitching, videspread appearance of perhaps only one in several thousand bites by large hives(angioneurotic ), , con- thesepresunably nonvenomouscolubrids results tractedpupils, and sensation ofyellow vision. All in poisoning. The answer may be in the maydevelop within an hour afterthe individual of the colubrid venom apparatus. Duvernoy's is bitten. gland, roughly the equivalent of the pit viper Coralsnake bites are not verypainful; there venomgland. has a highly toxic secrelionin al is little or no swellingand no discoloration.Fang least some colubrid snakes.But it has a very small puncturesbleed little and may be almostunde- lumen for venom storage.And a solid tooth is tectablea few hours after the bite. Character- not so effective for introducing venom into a isticallythere is an asymptomaticperiod that can as one that is grooved or hollow. When lastup to sevenhours. In fact,in abouthalf the a colubrid snakefeeds, it often holds and chews cases,no definitesigns of poisoningever develop. its prey. This gives time for Duvernoy's gland Not manycases of coralsnake bites have been to secretevenom which is worked into reportedin detail,but symptomsseem to be quite made by the teeth. It probably is significant that variable.Sometimes, there are painsradiating a majority of human by colubrids from the locationof the bite or in the abdomen. involve snakesthat hung on for severalseconds. Seriousmanifestations include drooping of the And in some cases,a captive snakebit when be- eyelids, difficulty in speaking and swallowing, ing offered food. generalizedmuscular weakness and incoordina- lion, drowsiness,and difficulty in breathing.This FirstAid and DefinitiveTreatment can progressto a completeand fatal paralysis. Statedsimply, the objectivesof snakebitetreat, A curiousand not well understoodphenom- mentare: (l) Removevenom before it cancom- enon is thal of venomousbites by presumably bine with targettissues. (2) Neutralize venom that nonvenomoussnakes of the family . cannot be removed.(3) Counteracteffects of Somecolubrids have enlarged, grooved fangs in venomthat cannotbe neutralized.(4) When all the rear of the upperjaw, and at leasttwo African the abovefail, repair the damage. speciesare unequivocallydangerous. A few specieswilh this type \enom apparatusjust Snakebitetreatment in theUnited States has enter the United States along the Mexican seen a number of colorful and downright border,and a few casesof mild venomousbites dangerousprocedures advocated, sometimes by by them havebeen reported. The most serious scientistsand physicians. In southern[ndiana in casesreported in the United Stateshave resulted the 1920's and 30's, whiskeywas a popular from bites of Asian snakessuch as the yama- remedylnearly every farmer kept a bottleor two "just kagashi ( tigrinus) and red-necked in case."Other populartreatments were keelback(R. subminiatus\pvchased as rnnocu- applicationof the split body of a freshly-killed ous pets (Mittleman & Goris 1974, Cable et al. chickento the bite or soakingthe bittenpan in l9B4).These snakes have enlarged but ungrooved keroseneor turpentine.First aid techniquesin- teeth in the rear of the upper jaw. Poisoningby volvingligature, incision, and suction have been thesesnakes results in a dramaticdecrease rn cer- widelyadvocated and are sound in principlebut

134 Minton of dubiousvalue in practice.Ligatures increase the bite and extendedup the bittenlimb to the painand have little effectin rctardingspread of trunk if thereis enoughbandage. I am told that venom. Incision followed by suction does pantyhose make an acceptablesubstitute. The facilitateremoval of somevenom. However, in- limb is thenimmobilized with a splint.The ban- cisionsmay damage large blood vessels, nenes, dagesare left in placeuntil the victirnreaches or tendons,provide entry for infection,and be the hospitaland preparations for beginningin- follovedby seriousblood loss particularly since travenousadministration of antivenomhave been many snake venomsmarkedly impair blood made.Both experimentaland clinicalevidence coagulation.Excision-cutting out the entire indicate the techniqueis quite effectivein areaaround a bite-is almostcertain to do more preventingabsorption of venomfrom a bitten harm than good and cannotbe recommended. limb (Sutherland1983, pp. 22'32).The rnethod Chillingthe areaaround a bite by useof ice or wasdeveloped in Australiawhere the important chemicalspray with or withouta ligatureis inef- snakeshave venoms that are highly lethal but not fective and can do seriousdamage if continued very destructivelocally. If usedfor treating bites for a prolongedperiod. Recently, electric shock by rattlesnakesand other pit vipers whose using high voltage,low amperagecurrent from venomscause significant local damage, it must an outboardmotor, lawn mower'or othet source be with the realizationthat generalizedpoison- hasbeen suggested as first aid for snakebite.The ing maybe preventedal lhe coslof increasing methodis underinvestigation but cannotcurent- local darnage.It is the recomrnendedprocedure Iy be advocated. for bites by coral snakeswhose venoms are more like thoseof Australiansnakes. As alreadymentioned, most persons bitten by snakescan reach definitive medical care within Another new technique is use of a trlo- 30-50minutes. Realizing this, I havemaintained charnberedsuction devicethat producesone at- for the last decadeor so that the most useful mospherenegative pressure. This is appliedto snakebitefirst aid kit consistsof car keys and the bite as quicklyas possible@itlro&, making somecoins for a call to a hospital.If at all pos' any incisions and left in place about three sible,the actualdriving to the hospitalshould minutes.Suction can be repeatedas necessary. be entrustedto someoneelse. The stressof driv- Preliminary animal experimentsindicate up to ing in traffic doesnot help a snakebiteand vice half an injecteddose of rattlesnakevenom can versa.Calling ahead is important.It givesthe be removed.The devicewas also tested on three emergencyroom time to pfeparefor the patient's personsbitten during a rattlesnakeroundup in arrival,and the physicianon duty can consull the Southwestwith apparentlygood results with colleaguesor call a PoisonInformation (Bronsteine, oL l9B5).Sawyer Products of Long Centerif he wishes.The snakeshould be brought Beach,California, markets the devicein a small, to the hospitalwith the victim if possibleso its light, durable kit suitable for field use. identitycan be verified.It is betterif the reptile Scientific evaluationof theseand other first is dead.A live snakein a hospitalemergency aid measureshas been possible through develop- roomis a ncpdlessdistra.tion and somelimes a ment of very sensitiveand specificenzymeJinked hazard.Identification is especiallyimportant if immunoassay(ELISA) for snake venoms.Af a coralsnake is suspected,for harmlessmimics thoughthese tests are not generallyavailable in ofcoralsnakes occur in manyparts of theUnited the United States,enough experimental work has States.In casesof bitesby exoticsnakes kept as been done to demonstratetheir valueboth in pets.idenlification of thereptile is v"ry impor' diagnosisof snakebiteand evaluationof treat' tant also. ment.Since the test can be donein abouttwo Tworelatively new procedures seem to be ef- hours,determining presence of venomin blood fectiveand safeenough that their use can be and urine can be helpful in distinguishinga cautiouslyadvocated for the small number of relativelyminor bite from a potentiallyserious snakebitesthat occurunder circumstances such one.These assays have also contributed to bet' that a delayof 30 minutesor more in reaching ter understandingthe pathophysiologyof snake a medicalfacility can be anticipated.0ne is the cnvenomation.One inlerestingohserration ic useof elasticbandages such as are widelyused that venomsof somesnakes can be detectedat to treatsprains w.apped snugly over the areaof the site of a bite after severaldays.

PoisonousSnakes and Snakebitein the U.S. 135 Althoughit is not the purposeof this review Exceptin mostunusual situations, to discusshospital management of snakebite, shouldbe givenin a hospital.This is but oneof somethingshould be saidabout antivenom. This numerousreasons why hospitalization ls recom- is the only clinically effectiveantidote for snake mendedfor all but obviouslytrivial snakebites. venompoisoning and is producedcommercially Blood pressureand other vital signsare more by hyperinmunizationof horseswith snake easilymonitored, and hypovolemicshock, the venoms.The product commonlyused in the commonestcause of deathin pit viperbites, can United Statesis madeagainst venoms of three be detectedearly and corrected,0ther dangerous speciesof rattlesnakesand a large neotropical complicationsof snakebitesuch as , pit viper of the genus . lt is at least renal failure, , and infection somewhateffective in neutralizingvenoms of all can alsobe detectedearly and dealtwith more North American pit vipers and the most impor- effectively,In a seriesof 9 fatal rattlesnakebites tant neotropicalspecies as well as those of a few in Arizona, two individuals refusedto go to the Old World ripers.A coralsnake antivenom is hospitaland three othersreached the hospital availablein limited quantity in thosestaies where after delaysof 1.5 to 29 hours(Hardy 1986). coral snakesoccur. are by no means A singlenonfatal snakebite confers no effec- ideal therapeutic agents. Their neutralizing liveimmunill. and eridenre of immu n ity in pro- capacityis relativelylow, hencelarge doses-400 fessionaland religioussnake handlers who have ml or more-sometimesmust be givenin a very survivedmany bites is equivocal.Some have died severeenvenomation. Not all venOmsand venom of snakebiteafter surviving len or moreprevious fractions are equally well neutralized. Anti- bites.Immunization with toxoid,a strategyhighly venomshave little effect against the factors in successfulin infections such as diptheria and pit viper venomsthat causelocal swellingand tetanus, has been attempted with detoxified .Being foreign proteins,antivenoms snakevenoms. The only large scaletrial, in the commonlycause serum sickness, less frequently Ryukyu Islands,was not particularly successful anaphylaxisand other forms of immunologicin- (Sawaiet al- 1969),but the procedureis being jury. Significantimprovement in antivenomscan consideredin someother regionsof very high be anricipated.Experimental antivenom pre- snakebiteincidence. In the United Statesit would pared by affinity chromatographyhas much bet- be appropriateonly for a very small number of ter neutralizingcapacity and is lesslikely to cause individuals.The bestsingle preventative measure (Russell et al, 1985).A commercial is to avoid deliberatecontact with veromous product could be availablein a relatively short snakes."Illegitimate" snakebites,those sus- time. Monoclonalantibodies have been produced tained by individualswho knowinglyplace them- against several toxins, but their selvesat risk, make up roughly half the snake- therapeuticuse has not beenexplored. bites reportedin the United States.

Literature Cited Clenn, J. L., R. C. Straighi, M. C. Wolfe, and D. L. Ha.dy. 1983.Geographical variariot in Crotdlusscututatus Bronstein,A. C., F. E. Russell,J. B. Sulliran,N. B. Egen, andB. R. Rumac\.1q85. Negarire pre*urp.u.rinn (Mojave rattlesnake) venom properties. Toxicon in field lrealneni of rattlesnakebite. Vet. Hun. Tox 2l:119-130. icol. 28:297,185. Hardy,D. L. 1986.Fslal rattlcsnakeenvenonation in Arizona. Cable,D., W. McCehee,W. A. Wingert, and F. E. Russell. J. Tox. Clin. Tox. 24:l 10. 1984. Prolonged defibrination after a bite fron a Kardong, K. V. 1986.Th€ predatorystrike ofthe rauiesnale: lnale. 251:925-926. JAMA when thinss so amiss.Copeia 1986:816-820. Fiero, K., M. W. M. Seifert,T. J. Weaver,and C. A. Bonilla. Minron, S. A. 1953.Variation in venom samplesfron cop- 1972.Conparative study ofjuvenile and adult prairie perheads and timber ratllesnakes.Copeia rattlesnake(Croralrs li'idrr !,r.d6) venoms.Toxicon t9531212-2].5. 10:81-82. t96?. Observationson tonicity and anligenic Ctenn,J. L. and R. C. Srraight.1982. The rattlesnakesand juvenile their venon yi€ld and lethal toricity. 1l[ Tu, A. T. makeup of venons of snakes.1N Russell, (ed.) RattlesnakeVenons: their Actions and Trear- F. E. and P. R. Saundere(eds.) Animal Toxins 0x- ment.New York. MarcelDekker. Pp. 3 119. ford. PergamonPress. Pp. 211222.

136 Minton