Postgraduate Medical Journal (December 1975) 51, 830-837.

Bites and stings in travellers

H. ALISTAIR REIDO.B.E., M.D., F.R.C.P.E., F.R.A.C.P., D.T.M. & H.

Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 SQA

SummaryAs a rule, bites and stings in travellers are merely anuisance. But it is sensible to be informed about themore serious possibilities which can result. Systemicdiseases can be transmitted, the skin lesions frominsects can be troublesome and finally, some bites andstings can cause envenoming. Thus, the bather may beharmed by venomous fish stings, sea urchins, jellyfishand in Asian-Pacific waters by sea-snakes. Landhazards include bites or stings by scorpions, spiders,ticks, centipedes, bees, wasps, caterpillars and snakes.The main clinical features of such bites and stings,including treatment and prevention, are outlined.

IntroductionFew, if any, travellers will escape bites or stings,

particularly if they travel to the tropics or sub-tropics. The catalogue of disasters associated withinsect troublemakers should alone be enough tomake one stay at home (Harman, 1971). Othercommon animals potentially noxious to the travellerinclude jellyfish, sea urchins, venomous fish, seasnakes, ticks, mites, scorpions, spiders, centipedes andland snakes. However, the traveller may take heartfrom statistics in Rhodesia where the annual deathrate from road accidents is seventeen times thatcaused by animals (Castle, 1971). Moreover most ofthe deaths caused by animals were provoked by manrather than by the animal. Undoubtedly, thegreatest animal danger to travellers is man (followedin Rhodesia by the crocodile). Bites and stings canharm the traveller, causing (1) trauma, physical andmental (fright), (2) transmission of systemic disease,(3) skin lesions, (4) envenoming.

Transmission of systemic diseaseSystemic disease is the most serious potential

harm to the traveller from bites and stings. Althoughthe diseases in Table 1 would be acquired in thetropics and sub-tropics, symptoms often start afterthe traveller has returned home. The most importantdisease is falciparum malaria, dealt with in theprevious paper.

TABLE 1. Diseases acquired by bites and stingsVector Systemic disease transmitted

Class INSECTAOrder DIPTERA

Mosquitoes Malaria, filariasis, arboviralinfections

Sandflies Leishmaniasis, bartonellosisBlackflies OnchocerciasisMidges FilariasisTsetse flies African trypanosomiasisHorseflies Loaiasis, tularaemia

Order ANOPLURALice Typhus, Q fever

Order SIPHONOPTERAFleas Plague, typhus

Order HEMIPTERABugs American trypanosomiasis

Class ARACHNIDAOrder ACARINA

Mites TyphusSoft ticks Relapsing feverHard ticks Typhus, arboviral infections

Dogs, bats, etc. Rabies

Skin lesionsInsect bites are a world-wide scourge to travellers

who can become rapidly sensitized so that firm itchypapules form within 24 hr of each bite-usuallymultiple bites. After further exposure immediateweals may develop and subsequent bites may provokeboth types of reaction indefinitely. Alternatively,reactions may decrease; first, the delayed and thenthe immediate responses are reduced or lost (Har-man, 1971). For local treatment calamine lotion issuitable; antihistamines can cause sensitization andphoto-sensitization and are not recommended. Butif lesions are widespread, antihistamines by mouthare probably helpful, such as chlorpheniraminemaleate tablets (Piriton) 4-16 mg daily. For moresevere local reactions a steroid such as betamethasonevalerate cream (Betnovate) may be needed-pro-vided there is no sepsis or ulceration. Infection ofscratched lesions must be discouraged, if necessaryby a bandage. If infection has been established,systemic and local antibiotics may be needed.

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Clothing helps to prevent insect bites especiallyround the ankles. A useful repellant is diethyltolu-amide in a liquid evaporating base such as 70%ethanol. An insecticidal aerosol spray is worthtaking on travels.

MyiasisThis is the condition produced by fly larvae in-

vading living tissue. The Tumbu fly, Cordylobiaanthropophaga, is widely distributed in Africa Southof the Sahara. The female fly lays eggs on sand orsoil contaminated by urine or excreta; larvae fromthe eggs can live 1-2 weeks in~the soil before theybecome attached to a host. They burrow just underthe skin, leaving their posterior breathing openingson a level with the surface. The lesions may appearonly on return from travelling and resemble boilsbut do not throb (although they itch), and each hasa small hole in the centre. The larvae grow in theskin for about 2 weeks then wriggle out to form apuparium. The adult flies emerge 10 days later;they resemble bluebottles except for a yellowishcolour. Man may acquire the larvae from con-taminated sand, clothes or bed linen. An adhesiveocclusive dressing kills the larvae which in time areshed naturally from the skin (Radcliffe, 1972).Larvae of several other flies can cause similar lesionsincluding subconjunctival lesions.

ChiggersThe chigger sandflea, Tunga penetrans, occurs in

tropical Americas, Africa and India. The impreg-nated female flea burrows into the skin of the firstwarm-blooded animal she encounters (in man,usually the foot), and grows to the size of a smallpea. A painful boil-like lesion with a central blackdot results, and secondary infection is common. Thebest treatment is to enlarge the entrance orifice witha needle and enucleate the entire insect. Walkingbare-footed should be avoided.

Venomous bites and stingsGeneral considerationsVenomous creatures can secrete venom in a gland

or in specialized cells, and can deliver this venomduring biting or stinging. All venoms contain acomplex mixture of toxins which can be experi-mentally fractionated into enzymes and polypeptideswith widely varying biological and pharmacologicaleffects. Readers interested in details ofvenoms shouldconsult the admirable review by Minton (1974). Thecomplex and sometimes conflicting experimentaleffects of venom fractions are not always relevant tothe clinical problem of envenoming in man. Indeed,some experimental findings can mislead clinicians.In man, the important clinical effects of venomous

bites and stings are fairly simple and may be dividedinto:

(1) Fright effects are present in virtually allvenomous bites and stings. Often there is fear thatrapid, painful death is inevitable.

(2) Venom effects may be summarized:(i) Local, mainly vasculotoxic (pain, swelling,

sometimes necrosis).(ii) Systemic vasculotoxic (bleeding, some-

times shock).(iii) Systemic neurotoxic (autonomic effects;

neuromuscular block of muscles for vision,swallowing, breathing).

(iv) Systemic cardiotoxic or myotoxic effects(less commonly).

Systemic vasculotoxic effects are typical of viperinesnakebite poisoning, and the neuromuscular blockingeffects are typical of elapid snake bite poisoning.Venoms of sea snakes and of some Australian elapidsnakes are mainly myotoxic. The venom effects ofbites and stings other than snake bite chiefly involvelocal vasculotoxic features, autonomic neurotoxicfeatures, and sometimes cardiotoxic effects. Ifpoison-ing is very severe, acute renal failure can occur inmost types of envenoming.Although the effects of venomous bites and stings

in man depend on the type of venom, a much moreimportant factor is the amount of venom injected.Clinicians should realize that, although fatalities andserious poisoning can occur, more commonly (andfortunately) little or no envenoming results fromvenomous bites and stings in man. In the latter cases,fear often dominates the clinical picture.

Venomous bites and stings in the seaFish stingsVenomous fish stings are common in the tropics.

In coastal waters where the sea bed is mud or sand,catfish occur-so called because they have whiskerymouthparts. They have serrated spines in their finswhich can inject venom. Stingrays have a flattriangular-shaped body varying in diameter from afew cm to 3 m. When trodden on they whip forwardtheir tail which has a serrated sting on it. In coralreefs, even more venomous fish are found such asstonefish and scorpion fish. They have multiplevenomous stings along their backs. The main effectsof stings by these fish is an intense and often agoniz-ing local pain. Sometimes the sting becomes de-tached and remains embedded, leading to a chronicdischarge. Local necrosis sometimes occurs withscorpion fish stings.The most effective treatment for the local pain of

venomous fish stings is hot water. The part stung isimmersed in water as hot as the patient can bear.The pain is relieved within seconds and the part

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stung must be quickly removed from the water toavoid blistering. It should be reimmersed as painrecurs (within seconds at first, later within minutes).This procedure should be continued until the painno longer recurs (usually about 30 min). It is im-portant to explain details of this simple but highlyeffective treatment to the patient, who should begiven a can of water recently brought to boilingpoint. This should be added to the immersing waterto keep it as constantly hot as he can bear. If thewater is not hot enough, the treatment is noteffective, but if the stung part is immersed too longin very hot water, blistering will result. If the partstung is unsuitable for immersion in hot water (forexample, the face or trunk), the area should beinfiltrated through the puncture wound with 2-5 mlof 1% lignocaine hydrochloride.

Sea urchinsSea urchins are globular, cushion-shaped, or

discoidal relatives of the starfish and are abundantin shallow tropical waters. They have numeroussharp, brittle, articulated spines, 3-30 cm long. Thespines are used for locomotion, digging and self-protection, and although no venom has so far beendemonstrated, the pain can far exceed that producedby mere mechanical injury. Sometimes generalsymptoms may follow in addition-giddiness, diffi-culty in breathing, weakness of lips, tongue, eyelidsand limbs lasting up to 6 hr. If the spines are notremoved they may cause sepsis and, after 1-3months, small, painless granulomatous nodules mayappear. Penetration of bone may cause cyst forma-tion, and joint injury can provoke severe destructivearthritis.

Spines should be removed as soon as possible.Over superficially embedded spines the thick keratinof the sole of the foot is excised and 2% salicylicointment is applied for 24-48 hr. The spines canthen be expelled through the soggy skin by vigorous,and not too painful, squeezing. More deeply em-bedded spines should be removed surgically afterlocal anaesthesia. Antiseptic dressings or antibioticsmay be required for a few days until the woundsheal.

Jellyfish stingsJellyfish have myriads of microscopic stinging

capsules called nematocysts on their tentacles. Whentouched, these capsules extrude a sting which caneject venom. However, only a small number ofjellyfish have stings which can penetrate intacthuman skin. The most dangerous jellyfish, thecubomedusan or box jellyfish, sometimes calledsea-wasp, is confined to tropical waters. Having acuboidal body or float, up to 20 cm in diameter, anda leash of several tentacles growing from each of the

four body corners, it is translucent and difficult tosee in the water. Sea-wasps of the family Chiro-dropidae, have been found in tropical waters of allcontinents in the world. Physalia, or the Portugueseman-o'-war jellyfish, has a coloured float from whichnumerous minor tentacles hang, together with asingle main tentacle which can be very long, up to30 m in length. Although it has an evil reputation,severe poisoning seldom follows the stings of thePortuguese man-o'-war, fatal stings being extremelyrare. In contrast, several deaths following stings bythe box jellyfish, Chironex fleckeri, have been re-corded from Australian waters. Death is due to rapidcollapse within a few minutes of the sting; theserapid deaths appearing to be more due to heartfailure than to respiratory failure. If the victim sur-vives for 30 min, death does not occur but the partsstung become swollen and, later, necrosis can ensue.A smaller cubomedusan causes the Irukandji sting,so-named after an Australian aboriginal tribe. Localsymptoms are minimal, but after 10-20 min, violentgeneralized pains ensue, with restlessness and sweat-ing. These symptoms may continue for 1-2 days.The Irukandji sting is never fatal.

Stings by most jellyfish other than sea-wasps causeonly local wealing with tingling and discomfort,usually lasting a few hours. Only a small proportion(about 10-20%) of the nematocysts discharge theirstings and venom, and this has important implica-tions for treatment. Methylated spirits (or any otheralcohol) should be applied to the stung parts to killthe undischarged nematocysts. If no alcohol isavailable, dry sand or any dry powder should bethrown on the sting and then the tentacles and slimeshould be scraped off. Dry sand is better than wetsand. The sting should not be rubbed with wet hands,cloth, and so on, as this will spread and aggravatethe sting. After the spirits have dried, calaminelotion is a suitable local application. In severe caseswith rapid collapse, the victim should be lain onhis back, methylated spirits poured on the sting,and tourniquets put on affected limbs. If breathingstops, mouth-to-nose artificial respiration should begiven; if the heart stops, closed-chest cardiac massageshould be carried out. A potent sea-wasp antivenomhas recently become available from the Common-wealth Serum Laboratories, Australia, and itsadministration has resulted in dramatic recoveryfrom severe poisoning by C. fleckeri stings (Baxterand Marr, 1974).

Sea snake biteSea snakes have very short fixed fangs and

characteristic flat tails. They are common only inAsian and western Pacific coastal waters, and do notoccur in the Atlantic ocean or the Mediterranean.Although sea snake venom is extremely toxic, one

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'drop' (0 03 ml) being sufficient to kill three adultmen, sea snakes rarely inject venom when they biteman. In a series of 103 patients with unequivocal seasnake bite, 80% had trivial or no poisoning. How-ever, if poisoning were present, the mortality ratewas 50% until effective antivenom became available(Reid, 1975a). It is thus very important for theclinician to distinguish sea snake bite from sea snakebite poisoning.The great majority of victims are fishermen bitten

at their work, but occasionally bathers and skindivers are bitten if they tread on or handle sea snakes.Sea snake bites have no important local effects-there is no swelling or pain and the pinprick marks ofthe bite may be difficult or even impossible to makeout. If venom is injected characteristic generalizedmyalgic pains start 30-60 min after the bite followedin a few hours by the red-brown colour of myo-globin in the urine. In severe poisoning the myalgicpains merge into paresis with inability to move theeyes, open the mouth, protrude the tongue orswallow. Respiratory insufficiency and hyper-kalaemia follow (tall peaked T-waves in chest leadsof the electrocardiogram). Fatal respiratory failuremay occur within a few hours of the bite from inhala-tion of secretions or vomit. In other cases whererespiratory failure is due to weakness of respiratorymuscles, death is usually 12-24 hr after the bite. Inthe absence of effective antivenom, the myotoxiceffects are prolonged and full recovery may takeseveral months. In such cases, acute renal failureis the rule.

In treating sea snake bites, adequate reassuranceis most important and a placebo injection shouldbe promptly given unless clear signs of poisoning arealready evident; in this event effective antivenomshould be given. If used correctly antivenom can beeffective even though not given until hours after thebite (Reid, 1962). Both tiger snake antivenom andsea snake antivenom (Commonwealth SerumLaboratories, Melbourne) are effective (Baxter andGallichio, 1974). Antivenom (1000-10,000 u) shouldalways be given by intravenous infusion, which isthe most effective and the safest route. Details ofantivenom administration and supportive treatmentare given elsewhere (Reid, 1972b; 1975a).

Bathers in regions where sea snakes can occurshould follow the example of fishermen and shuffle,rather than walk, on the sea bed. Bathers are quitesafe swimming in the sea, and therefore should keepswimming as far as possible. Divers should ignoresea snakes and on no account attempt 'sportingly' tocatch them. Amateur fishermen should treat seasnakes with great respect; although they may seemdocile most of the time, it would be extremelyfoolish to rely on their reluctance to bite man. Insome regions, sea snakes may be caught by amateur

fishermen using a line and hook, in which case theline should be cut and the sea snake dropped into thewater-without handling. If a sea snake finds its wayby net or line into a boat, no attempt should be madeto kill it. The sea snake should be lifted sharply bythe tail, held at arm's length with regular shaking ofthe hand (this is most effective in keeping the seasnake vertical and stopping it 'climbing up itself' tobite the hand), and then thrown into the sea.

Venomous bites and stings on landScorpion stings

Scorpions have four pairs of legs, a pair of claws,a body with broader front part and a 6-jointed tail-like abdomen. The terminal segment, called thetelson, contains two venom glands connecting withthe curved, needle-sharp sting which is used either indefence or in obtaining food. The tail with its stingis always brought forward in front of the scorpion.Scorpions never sting backwards and this featureenables safe handling of scorpions (provided one isfamiliar with their habits). The length of adultscorpions varies from < 2 cm up to about 20 cm,but the length of the scorpion does not relate to itsdanger to man. Some of the most dangerousscorpions to man are only 2-4 cm long. Mostscorpions are nocturnal, and feed on spiders andinsects. During the daytime, they hide under logsand rocks, in cracks, among debris, clothing, etc.There are some 350 different species of scorpion.Probably the five most dangerous scorpions to manare: Centruroides (southern United States, CentralAmerica), Tityus (South America), Androctonus(Africa), Leiurus (Africa and Middle East), andButhus (Asia). There are no reliable statistics indi-cating the frequency and danger of scorpion stings.In Israel, Efrati (1949) recorded that despite seeingscores of stings by Leiurus scorpions every year, hehad observed only twenty-two cases of seriousgeneralized poisoning during 12 years. In southIndia, no fatal cases were seen at a hospital where800-1000 scorpion sting victims attended each year(Roantree, 1961). However, in some parts of thetropics, scorpion stings appear to be more importantclinically than snake bite. This is said to be so inMexico where Centruroides is alleged to have killedover forty victims each year in Durango, a small cityof only 40,000 inhabitants. In Trinidad and SouthAmerica, stings by Tityus are common and aresometimes fatal.The clinical features depend mainly on the amount

of venom injected relative to the weight of thevictim. Local pain and fright are the most commonresults and this is all that happens in the great majorityof stings. Pain can be severe and may last some hours,even 1-2 days. Local redness and swelling are un-usual. General symptoms are exceptional but are

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more common in younger victims. They suggest an'autonomic storm' and include rapid breathing,salivation, sweating, vomiting, abdominal andgeneralized pains, and, in very severe poisoning,falling blood pressure and pulmonary oedemaprobably due to cardiotoxic effects. The latter canbe fatal in children. In such cases various electro-cardiographic abnormalities have been recorded.Evidence of acute pancreatitis is common withTityus stings-abdominal pain, glycosuria, raisedblood sugar and raised serum amylase. In India,evidence of intravascular coagulation has beenreported in Buthus stings.

If local pain is severe, the area should be infiltratedthrough the puncture wound with 2-5 ml of 1%lignocaine hydrochloride. Alternatively, intramus-cular or intravenous pethidine should be given,100 mg for an adult, 2 mg per kg for children. Localinjection of emetine hydrochloride has been reportedas successful in relieving pain but is not recommendedbecause it sometimes causes local necrosis (Cutting,1963). For the general systemic symptoms, specificscorpion antivenom is available in a few parts of thetropics (Reid, 1975b). When antivenom is not avail-able, general supportive treatment is indicated. Sub-cutaneous atropine (for adults 2 mg; 6-12 years0-5-1 mg; 1-5 years 0-25-0-5 mg; up to 1 year0-25 mg), and intravenous calcium gluconate (1-2 gfor adults; 06-1 g for 6-12 years; 0-3-0-6 for under6 years) have been reported as effective by someclinicians.

Spider bitesSpiders have a pair of horny fangs (chelicerae)

through which venom can be injected. But fewspiders can pierce human skin, and most are re-luctant to bite man. As with scorpions and manysnakes, the harmfulness of a spider cannot be judgedfrom its appearance. Many of the large browntarantula-like spiders are harmless to man. Per-haps the most dangerous are the widow spidersof the genus Latrodectus found in most tropical andsub-tropical countries. Adult Latrodectus bodiesmeasure only about 1 cm in length. Another bitinggenus, Loxosceles, is brown and about the same sizeas Latrodectus; it is common in the Americas. Bothsexes are venomous.Man encounters spiders in dark, neglected places

such as barns, stables and unused buildings. Black-widow spiders may spin webs across latrine seats,and it is reported that in Texas 90% of spider bitesoccur in outside privies. Latrodectus poisoning causesexcruciating cramp-like pains in the limbs, chest, andabdomen. Sweating, breathing difficulty, salivation,nausea, and vomiting may follow. Ptosis has beenrecorded, and in severe poisoning an itching rashmay erupt over the trunk or around the site of the

bite. Symptoms usually start within a few minutesof the bite, and within 30 min the victim may beunconscious. Abnormalities in the electrocardiogramhave been observed, and death may be due to cardiacor respiratory failure. Recovery is usually completewithin 24 hr but may take up to a week. The clinicalpicture following Loxosceles bites is quite different.Local pain is severe, and a white, intensely ischaemicarea at the site of the bite is surrounded by rednessand extravasated blood. The white area turnsviolaceous, then black and dry. The eschar separates,leaving a deep ulcer. In severe cases. haemoglobin-uria, intravascular coagulation, and acute renalfailure may occur.Treatment of spider bites is similar to that of

scorpion stings. A multitude of remedies has beenproposed but controlled studies are notably lacking.Latrodectus antivenom (available from Common-wealth Serum Laboratories, Melbourne; Merck-Sharp and Dohme, Philadelphia, U.S.A., and fromthe South African Institute for Medical Research,Johannesburg) has been reported as clinically useful,but the results were not as dramatic as with calciumgluconate. Other measures advocated for latrodectisminclude muscle relaxants, adrenaline, atropine, andchlorpromazine. Steroids have received favourableand unfavourable comment. In Loxosceles poisoning,no benefit was noted with prednisone. Antibacterialmeasures including early excision of eschars andskin grafting are helpful. If renal failure develops,dialysis might be needed. Loxosceles antivenom isavailable in Brazil, but clinical reports of effective-ness are lacking.

Tick paralysisHard ticks have a neurotoxic saliva which can

cause a rapid progressive flaccid paralysis in manand certain other mammals. Human tick paralysishas been reported from Canada, United States,south-east Europe, South Africa, Somaliland, andAustralia. Symptoms start 4-6 days after attach-ment of the causative tick and may therefore notdevelop until the traveller has returned home.Anorexia and ataxia are followed by flaccid paralysisof legs, trunk, arms, and neck in that order. Tendonreflexes are decreased or absent; sensory changes areminimal or lacking. Fatal bulbar or respiratoryparalysis may develop, mortality in some series oftick paralysis being 10-12%. Removal of the tick,which is usually attached to the scalp or neck, iscurative, and improvement may begin within anhour, recovery usually being complete within 48 hr.Travellers to tick-infested areas who are likely tointrude on tick habitats by camping, picnicking andso on, should look for ticks at the end of each day,especially where children are concerned.

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Centipede bitesThe body of a centipede has a series of similar

segments each possessing a pair of legs. The head hasa pair of antennae and associated mouth parts. Thesegment immediately behind the head has a pair ofclaws through which venom is injected when thecentipede bites. Numbers of leg pairs vary fromfifteen to over a hundred; in the tropics somecentipedes exceed 25 cm in length. Bites can causeintense pain and treatment is similar to that forscorpion stings.

Bee, wasp and hornet stingsHoney bees have a barbed sting which is left

behind together with the venom sac, but wasp andhornet stings are not barbed and are therefore notleft behind. Bee venom contains many toxic fractions,the most important being mellitin which alterscapillary permeability, causes local pain and inflam-mation, haemolyses erythrocytes, and lowers bloodpressure. Local pain is the commonest clinicalfeature of these stings but with multiple stings, generalsymptoms with haemoglobinuria or myoglobinuria,and acute renal failure may develop. Deaths havebeen reported after only 30-60 stings by the honeybee, but usually 400-500 stings are necessary toproduce death in an adult, and survival after 2243stings has been reported (Murray, 1964).The most serious aspect of wasp and bee stings is

allergic reaction (Barr, 1974). In the United Statesthere are more deaths from anaphylaxis followingwasp or bee stings than from all other venomousbites or stings combined together. In very susceptiblepatients symptoms start after a few seconds withtingling of the scalp, vasodilatation, hypotension,and death within 1-2 min. In most patients, however,the reaction begins in 1-2 min with generalizedurticaria, followed during the next hour by oedemaof the glottis, bronchoconstriction, hypotension, andcoma. Once an immediate reaction has occurred,the response to further stings starts progressivelysooner and the severity of the shock increases.Delayed allergic reactions may also occur, comingon 1-7 days after the sting-fever, urticaria, enlargedlymph nodes, joint pains and leucocytosis. Theseepisodes usually last 1-2 weeks.The bee sting should be removed. It is a tiny black

shaft with the white poison sac attached to its freeend. It should not be grapsed by forceps or fingers asthis can express more venom from the sac. The stingshould be scraped from the flesh with the finger-nailor the blade of a knife. Local antiseptic is thenapplied; pethidine may be needed for pain. It hasbeen claimed (Arnold, 1972) that meat tenderizer,available in most kitchens, applied in a dilute solution(quarter-teaspoonful of tenderizer mixed with ateaspoonful of tap water) rubbed into the skin

relieves all pain within seconds. The effect presumablydepends on the content of papain which breaks downvenom and kinins at the sting site. Adrenaline isindicated for anaphylactic reactions, either byinjection or by inhalation. Inhalation ofan adrenalineaerosol (Medihaler EPI, Riker) from a pressurizedcan similar to that used for asthma is more rapidthan administering an injection. Five inhalations ofthis aerosol are equivalent in effect to 0 5 ml ofinjected 1: 1000 adrenaline. People who are knownto be allergic to bee or wasp stings should alwayscarry such a can. Desensitization can be done butthis is usually temporary unless maintenance de-sensitizing injections every 1-4 months are continuedindefinitely.

Caterpillars, moths and beetlesSome caterpillars and moths have sharp hairs

or spines which contain venom. Examples arepine caterpillars (Thaumatopoea) and processionarycaterpillars (Ctenocampa) in Europe and the Mediter-ranean area, puss caterpillars (Megalopyge oper-cularis) in the United States, Hylesia moths andcaterpillars in South America. Outbreaks of cater-pillar dermatitis usually occur in the summer months.Symptoms produced by contact with urticarialspecies may be restricted to reddening and itchingbut may include burning pain, swelling, blistering,conjunctivitis, vomiting, headache, paralysis andshock. Prompt application of scotch tape can removemany spines; lotions or creams with steroids relievethe skin reactions. Antihistamines are of little value.

Blister beetles of the Meloidae family can exude avesicant on injury. Small rove beetles (Paederus) flyduring the evening and are common in humidclimates. When crushed or rubbed on the skin,erythema results about 10 hr later followed by acrop of small blisters which persist for about twodays.

Land snake bitesSnake bite as a holiday hazard in Europe, the

Near East, North Africa and the West Indies(Reid, 1971) and snake bite in the tropics (Reid,1972a, b) have been considered elsewhere and thehazard of land snake bite to the traveller will onlybe summarized in this paper. Snake bite is a ruraland occupational hazard and travellers, even to thetropics, can be reassured that they are most unlikelyto see, let alone be bitten by snakes. If a travellerdoes get bitten it is usually his own fault (e.g. bypicking a snake up).

Vipers and elapids. Medically important landsnakes have fangs at the front of their mouths whichenable them to inject venom. These are the'poisonous' snakes of which there are two families

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-elapids (neurotoxic), and vipers (vasculotoxic).Elapids have short fixed fangs (covered by a gum-fold, the vagina dentis). Vipers have long, erectilefangs, triangular heads, and, usually, short fatbodies. Vipers are subdivided into crotaline or pitvipers, having a thermosensitive pit between eyeand nose, and viperine vipers, without pits. The pitdetects warm-blooded prey in the dark. All snakevenoms are highly toxic, but when a venomoussnake bites man it is a defensive or warning bitewhen little or even no venom is usually injected,hence most human victims do not have seriouspoisoning. Only about 25% will develop systemicpoisoning. Therefore poisonous snake bite is notnecessarily the same as snake bite poisoning. Fear invarying degrees is present in all victims bitten bysnakes and often dominates the clinical picture.

Early effects of envenoming. Local swelling startswithin a few minutes of a viper bite if venom isinjected. It is a valuable clinical sign, because ifswelling is absent and one knows the biting snake wasa viper then poisoning can be immediately excluded.Local swelling is also a feature of poisoning byAsian cobra bites and African spitting cobra bites,though it may not appear for 1-2 hours. Otherelapids (such as mambas and kraits) have no localeffects. Local pain almost invariably follows cobraand viper bites if venom is injected, and it may besevere for several days. But local pain may be mini-mal or absent in severe poisoning, and considerablein bites not involving poisoning; thus local pain isextremely variable and of no help in diagnosis.The important early signs of systemic poisoning

are: viper-blood-stained spit, later non-clottingblood; elapid-ptosis, glossopharyngeal palsy. Non-clotting blood is best detected using a capillary tubewith blood taken from a finger prick. The tube shouldbe kept horizontal at room temperature for 20-30min and then raised vertically. Non-clotting bloodruns out of its own accord or can easily be blown out.There are exceptions to these generalizations. Thetropical rattlesnake has neurotoxic, not haemor-rhagic, effects although it is a pit viper. SomeAustralian elapid snakes have myotoxic, vasculo-toxic, and coagulation effects although they areprincipally neurotoxic. Some vipers (such as thepuff adder and the gaboon viper in Africa) do notaffect clotting in human victims.

Later effects of envenoming. Blisters around thesite of the bite are common in cobra and viperenvenoming, and blisters extending up the limbsuggest a large dose of venom and often precedenecrosis. Local necrosis is characteristic of poisoningfrom Asian and African spitting cobra bites andsome viper bites (such as the African puff adder).It becomes evident a few days after the bite and isshown by a darkening of the skin together with an

offensive 'putrid' smell, which is particularly markedin cobra bite necrosis. Necrosis can be extensive butit is usually superficial; involvement of tendons,muscle and bones is exceptional. Bacterial infectionfollows necrosis and may spread to joints. But inthe absence of necrosis or meddlesome localmeasures such as incision, application of dressings,etc., bacterial infection virtually never occurs.

Prognosis. Viperine poisoning is severe if within1-2 hr of the bite swelling is above the knee orelbow, shock is evident, or haemorrhagic signs be-sides haemoptysis develop (gum bleeding, ecchy-moses, positive tourniquet test and so on, do notusually appear for 4-5 hr). Elapid poisoning issevere if neurotoxic signs start within 1 hr or lessof the bite and rapidly progress to respiratoryfailure. Mental confusion strongly suggests respira-tory failure, although ptosis and glossopharyngealpalsy can make assessment of mental awaremessdifficult. Shock may also be a feature of severe elapidpoisoning. The laboratory findings in snake bite aredetailed elsewhere (Reid, 1974). Polymorph leucocy-tosis indicates serious poisoning. Even withoutspecific treatment the mortality in snake bite is low.Generally speaking, deaths are most rapid afterelapid bites, especially cobra bites (average deathtime is about 5 hr after the bite) and more protractedafter viper bites (average is 2-3 days after the bite).In elapid bite, death is mainly due to cardiorespiratoryfailure; shock, and haemorrhage into vital organsare the main causes of death in viper bites.

Clinical course of envenoming. In the absence ofnecrosis, pain after viper bites rarely exceeds 2 weeks.Swelling usually resolves completely in 2-3 weeks,rarely in 2-3 months, and in exceptional cases thelimb may remain permanently swollen. If blisters areleft alone and no dressing is applied, they rupturespontaneously about two weeks after the bite anddry up in another 1-2 weeks. If dressings are applied,infection usually follows and greatly prolongs heal-ing. Healing of local necrotic lesions varies accord-ing to the extent of the lesions and the treatmentgiven, but requires at least a month, and may take5-6 months or longer even with expert surgicalattention. In patients who recover without receivingspecific antivenom, systemic symptoms generallysubside quickly. Neurotoxic features of elapidsystemic poisoning resolve in 2-3 days as a rule, butexceptionally may persist as long as 2 weeks. Insystemic viper bite poisoning shock and haemor-rhagic features generally resolve within a week, butin bites by some vipers coagulation changes maypersist for 2-3 weeks or even longer if specific anti-venom is not given. Complications of systemicpoisoning are rare. Renal failure may occur withbites by all types of poisonous snake-vipers, elapids,or sea snakes. Neglected local necrosis can result in

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Bites and stings in travellers 837

chronic osteomyelitis with sinuses discharging foryears. Scarring may be extensive.

First-aid treatment. This comprises the measurestaken by the victim or associates before receivingmedical treatment. Recommendations (it will berare indeed for the doctor to have to apply thempersonally) should be short, simple, practicable andmore helpful than harmful. Reassurance is mostimportant, as the danger of snake bite is greatlyexaggerated. The site of the bite should not be in-cised, as this frequently introduces infection, delaysrecovery and aggravates bleeding. A firm, but nottight ligature should be applied just above the bite,using cloth, handkerchief or grass. The victim shouldthen go to the nearest hospital. If available, aspirinor alcohol in moderation is helpful. If the snake hasbeen killed it should be taken to hospital; otherwiseit should be left alone, since attempts to find or killit often result in further bites. Antivenom shouldplay no part in first-aid treatment.

Hospital treatment. Details of the hospital treat-ment of snake bite are given elsewhere (Reid, 1974)but it must be emphasized that antivenom is indicatedonly to counteract systemic poisoning (and ifcorrectly used, antivenom is very effective in doingthis) and to prevent or to minimize local necrosis inbites by known necrotizing snakes such as the puffadder when the patient presents within two hours ofthe bite.

Prevention. This is a matter of common sense.Boots give more protection than shoes. Whenwalking in the dark, a torch should be used. Camp-ing should be on open ground and, preferably,trenches should be dug around the tent and filledwith lime. Food should be kept separate from thesleeping area-it attracts rodents which in turnattract snakes. If a snake is encountered it is saferto keep perfectly still; the snake will then be unable

to strike toward the movement it requires, and canbe distracted by throwing down some object.

ReferencesARNOLD, H.L. (1972) Immediate treatment of insect stings.

Journal of the American Medical Association, 220, 585.BARR, S.E. (1974) Allergy to Hymenoptera stings. Journal of

the American Medical Association, 228, 718.BAXTER, E.H. & GALLICHIo, H.A. (1974) Cross-neutralisa-

tion by tiger snake (Notechis scutatus) antivenene and seasnake (Enhydrina schistosa) antivenene against several seasnake venoms. Toxicon, 12, 273.

BAXTER, E.H. & MARR, A.G.M. (1974) Sea-wasp (Chironexfleckeri) antivenene: neutralising potency against thevenom of three other jellyfish species. Toxicon, 12, 223.

CASTLE, W.M. (1971) A survey of deaths in Rhodesia causedby animals. Central African Journal of Medicine, 17, 165.

CUTTING, W.A.M. (1963) Treatment of scorpion sting.British Medical Journal, 1, 475.

EFRATI, P. (1949) Poisoning by scorpion stings in Israel.American Journal of Tropical Medicine, 29, 249.

HARMAN, R. (1971) Insect bites and stings. Practitioner,206, 595.

MINTON, S.A. (1974) Venom Diseases. Charles C. Thomas:Springfield, U.S.A.

MURRAY, J.A. (1964) A case of multiple bee stings. CentralAfrican Journal of Medicine, 10, 249.

RADCLIFFE, W. (1972) Tumbu fly. British Medical Journal, 2,164.

REID, H.A. (1962) Sea snake antivenom: successful trial.British Medical Journal, 2, 576.

REID, H.A. (1971) Snake bite as a holiday hazard. Practi-tioner, 206, 603.

REID, H.A. (1972a) Snake bite. Part I: Clinical features.Tropical Doctor, 2, 155.

REID, H.A. (1972b) Snake bite. Part II: Treatment. TropicalDoctor, 2, 159.

REID, H.A. (1974) Venomous bites and stings. In: Medicinein the Tropics. Ed. A. W. Woodruff; chapter 33, p. 541.Churchill Livingstone, Edinburgh and London.

REID, H.A. (1975a) Antivenom in sea snake bite poisoning.Lancet, i, 622.

REID, H.A. (1975b) Venomous bites and stings. TropicalDoctor, 5, 12.

ROANTREE, W.B. (1961) Scorpion stings. British MedicalJournal, 1, 1395.

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