STINGS/ ENVENOMATION

TERRESTRIAL ENVENOMATION: Snakes, scorpions, spiders and stinging insects.

(1) Snakes - Snake venom contains a mixture of pharmaceutically active substances  that can affect various body systems. Venom  is usually delivered by fangs located in the upper jaw of the snake. Some (spitting cobra) can spit venom.

Epidemiology - fatal snake bites total  50,000 -100,000 deaths per year worldwide.

Population at risk - native farmers, plantation gatherers, hunters, and field workers. Major risk areas include West Africa (Nigeria 12 % mortality), Indian subcontinent (Sri Lanka 10% mortality), southeast Asia, Latin America, Australia.

Two Medically Significant groups of Snakes - Elapids and Vipers.

Elapids - cobras, mambas, coral snakes, Australasian snakes, adders, kraits.

               - carry neurotoxic venom and can cause respiratory failure.

Vipers   - rattlesnakes, Russell's viper.

               - venom causes severe local effects and changes in the blood with systemic bleeding.

Clinical Features of snake bites - redness, swelling, necrosis.

                                                          *- changes in blood clotting.

                                                          *- paralysis (respiratory).

                                                            - anaphylactoid reactions

                                                                        *main causes of death.

Treatment of Snake Bite -

(1) Calm reassurance.

(2) Remove rings

(3) Immobilize/ splint limb

(4) Crepe bandage or pressure pad if venom is neurotoxic (Elapid bite) but caution if swelling.

(5) Identify snake if possible, in case antivenom required.

Antivenom - can be monospecific or polyspecific.

                     - carries risk of allergic reaction, therefore administered by experienced medical professionals with ability to give adrenaline, do CPR.

                     - indications for antivenom include neurotoxic effects, spontaneous bleeding, cardiovascular abnormalities, loss of consciousness, or rapid swelling and necrosis.

Prevention  - wear socks, boots, long pants,

                      - use flashlight at night, especially after rains.

                      - avoid long grass, sand, wood piles, rock, and overgrown lakes and rivers.

(2) Scorpions and spiders - both belong to the arachnids, which are animals having 8 legs.

Scorpions - have large pincers in front and venomous sting on the tip of their tail which arches over to sting its victim.

Population at risk - residents of all continents, but especially, southwest USA, Mexico, Brazil, Trinidad, North Africa, Near and Middle East, South and Central Africa, Indian subcontinent. In Mexico, scorpions kill 10 times as many people as do snakes. Kids are high risk for death from scorpion stings.

Clinical Features - very painful sting, with venom affecting nervous system, causing sweating, vomiting, diarrhea, low blood pressure, heart +/- respiratory failure.

Treatment  - lidocaine (anaesthetic) block, analgesics for pain.

                      - medical treatment,

                      - antivenom available (controversial).

Prevention  - shake clothes, bedding, shoes.

                       - bed net at night.

                       - wear shoes.

                       - clear sites, wear gloves.

Spiders - deliver venom from small fangs near their mouths. The most dangerous are: (1) Tarantulas (Mediterranean), Black widows (North American) and Red Back (Australia), all from the same genus.

                             (2) Banana spiders from South America.

                             (3) Funnel spiders from Australia.

                             (4) Brown Recluse spiders.

Clinical Features - spider venom can be either

(1) Neurotoxic - causing muscle spasms, or affect autonomic nervous system (anxiety, salivation, high blood pressure) (e.g., black widow, banana and funnel web), or:

(2) Cause local tissue destruction e.g., Brown recluse spider.

Treatment - crepe bandage +/- tourniquet to prevent spread to nervous system.

                     - ice, local anaesthetic to decrease pain.

                     - antivenom may be available.

Prevention - Clear sites, seal holes, use bed nets,

                     - check clothing, bed, bananas.

(3) Hymenoptera -stinging insects include 2 main groups;

(1) Apids - honeybees, bumblebees.

(2) Vespids - wasps, yellow jackets, hornets, fire ants.

These insects sting by means of a venom sac and stinger. Honeybees and some vespids leave the stinger at the sting site. The venom sac and stinger must be removed without squeezing.

Epidemiology - 40 people die annually from insect stings in the USA (50 % are from honeybees). Death is usually from an allergic reaction to the venom.

Clinical Features - Sting effects can be local or systemic.

(1) Local effects are due to venom and can be small or large/ immobilizing a limb. 10-15 % of people with large local reactions may develop anaphylactic reactions with future stings.

(2) Systemic Reactions - can be several types:

            (A) Toxic - non-allergic. Death can occur from 500-1500 stings.

            (B) Anaphylactoid - resemble anaphylaxis, but not IgE-mediated.

            (C) Anaphylaxis - occurs in about 1 % of population, due to previous sting sensitization and IgE mediated release of histamine. Often occurs within 10 minutes of sting, and can be associated with flushing, hives, swelling, upper and lower airway symptoms, shock and death.

Treatment of Stings -

(1) Local reactions - remove stinger without squeezing,.

                                  - ice, antihistamine, analgesic.

(2) Systemic reactions - treated as anaphylaxis with adrenaline (SC or IM), antihistamine, emergency transfer and medical management.

Medi-Alert information and an Epipen should be carried by anyone with a large local reaction, previous anaphylaxis, or known allergy to insect venom.

Other Bites - Various other "bites" have not been covered in detail in this study module. These include: bedbugs, fleas, jiggers, lice, mites, ticks, tumbu/botfly, reduvid/kissing bugs, millipedes, centipedes, caterpillars and leeches.

AQUATIC/ MARINE ENVENOMATION  - jellyfish, octopus, sea cones, venomous fish, and sea snakes.

(1)Jellyfish (Coelenterates) - sting by means of stinging cells (nematocysts) located on their tentacles. These discharge on contact with a person. Several species are lethal.

(A) Box jellyfish (cubozoans) - found in warm oceans (Indo Pacific, Atlantic, Caribbean), Thailand (Gulf of Siam/Thailand, Andaman Sea), Australia, Philippines, and Japan.

2 main dangerous box jellyfish are:

(1) Chironex fleckeri - multi-tentacled (chirodropids)

                                      - long tentacles up to 3 metres, leave ladder-like welts.

                                      - "most deadly animal in the world", with 70 deaths in Australia, and estimated 20-50 deaths annually. 2 recent deaths occurred in Thailand (Hat Rin Beach on Ko Phangan and a beach on Ko Samui).

Clinical features - instant severe pain.

                               - cardiac and respiratory arrest (can occur in minutes)

Risk factors - summer, warm water,

                       -  female, kids, (less hair)

                       - swimming after sunset (can't see them).

Treatment - get out of water.

                    - call 911, commence CPR.

                    - pour vinegar over sting for  30 seconds/ or pull tentacles off with fingers.

                    - cold packs to decrease pain.

                    - +/- compression bandages over major sting area.

                    - emergency treatment with oxygen, analgesia.

                    - Chironex Antivenom available in Australia at:

                                    CSL 45 Poplar Rd.,

                                    Parkville 3052,

                                    Victoria, Australia.

                    - also may be available on site in high risk areas, Queensland etc.

(2) Carukia barnesi (Irukandji)- small, thumb size box jellyfish.

Clinical features - "Irukandji syndrome" with mild symptoms followed 30 minutes later with severe unbearable pain, cramps all over, then symptoms of "sympathetic overdrive" (sweating, anxiety, headache, nausea, increased heart rate, and respiratory rate, and increased blood pressure).

Treatment of Irukandji - as with other box jellyfish, but definitive treatment in hospital to reverse catecholamine excess.

(B) Other venomous jellyfish include Portugese Man -0'-War, found world wide, the sand jellyfish (Stomolophus) found in south China seas, and Gonionemus, a small jellyfish found in the Sea of Japan.

Treatment - Do not use vinegar with these jellyfish. Flush off tentacles with sea water for initial treatment.

General Treatment Principles for Jellyfish Envenomation:

(1) Cold pack

(2) Vinegar to prevent more stings (ONLY in box jellyfish).

(3) Compression/ immobilization to decrease spread of venom.

(4) CPR, 1st aid.

Prevention -  Caution in warm weather, known sites, tropical seas.

                    -  avoid swimming in tropical areas after sunset, in calm seas.

                    -  observe warnings, use netted beaches, lycra 'stinger suits'.

Venomous Fish -  Venomous fish include shark, dogfish, stonefish, sting rays, and mantas, which have venom glands in spines on their fins or tails, and are dangerous if stepped on.

Sting rays - have sharp barbs, cause lacerations, death.

                    - found worldwide in tropical and sub tropical waters.

Stonefish - spines on its back, seldom fatal, antivenom available.

Clinical features - Both these fish can cause severe pain, nausea, vomiting and other symptoms.

Treatment - Bring ashore.

                    - hot water immersion (45 degrees) to destroy thermolabile toxin.

                    - lidocaine block for pain control

                    - CPR

Prevention - avoid wading in coral reef or shallow water.

Molluscs - 2 main dangerous ones.

(1) Blue ringed octopus - Indo Pacific area, Australia (including Sydney area).

Clinical features - contains tetrodotoxin.

                               - causes numb lips, tongue, and respiratory failure.

Treatment - CPR, assisted  ventilation up to 12 hours (patient remains alert).

                    - compression bandage.

(2) Cone shell - Indo Pacific area. Conical shell with long slit.

Clinical features -  pain, blanching, numbness, swelling.

                                - muscular weakness, respiratory paralysis, can be fatal.

Treatment - compression bandage, CPR.

Sea Snakes - found in oceans (India, Africa, Persian Gulf, Australia, New Zealand, South America, Pacific Coast) and fresh water (mouths of rivers).

                       - Sea snakes have a flat tail and small fangs.

Risk - fishermens' nets, or wading in shallow water.

Clinical features - initial bite painless,

                              - then muscle paralysis, respiratory failure, renal failure.

                              - 3% fatality rate ( 150 deaths annually).

Treatment - compression bandage,

                    - Antivenom (can use Tiger snake venom if sea snake venom not available).

                    - CPR, dialysis.

Overall Treatmentof Marine Envenomation (Vertebrate and Invertebrate):

(1) Cold packs to decrease pain.

(2) Hot water pack for penetrating barbs (rays etc.)

(3) Vinegar to decrease chirodropid (box jellyfish) venom.

(4) Compression/immobilization to decrease venom spread.

References:

Don't Drink the Water.

J.S.Keystone, M.D.

2000.

Travellers' Health.

Dr. Richard Dawood.

1992.

Dangers in the Ocean: The Traveller and Marine Envenomation I. Jellyfish.

Peter, J. Fenner.

Journal of Travel Medicine.

Vol.5. No.3. Sept. 1998. 135-141.

Dangers in the Ocean: The Traveller and Marine Envenomation II. Marine Vertebrates.

Peter, J. Fenner.

Journal of Travel Medicine.

Vol.5.No.4 Dec.1998..213-216.

Venomous Bites and Stings,

D. A . Warrell,

P. J. Fenner.

British Medical Bulletin.

Vol.49.No.2.1993. 423-439.

Lethal Irukandji Syndrome in Queensland, Australia.

Travel Medicine Advisor Update. P.21.

May/June 2002.

Textbook of Travel Medicine and Health,

2^nd.Ed.

DuPont and Steffen.

2001. 376-389.

Prepared by Dr. Caroline Penn,

Travel Medicine and Vaccination Centre,

314-1030 West Georgia St.,

Vancouver, B.C.

V6E2Y3.

Feb. 2003.

cmpenn@sfu.ca