Chapter XIV.11. Envenomations, Bites and Stings
Coral W. Yap, DO
July 2015

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The editors and current author would like to thank and acknowledge the significant contribution of the previous author of this chapter from the 2004 first edition, Dr. Todd T. Kuwaye. This current second edition chapter is a revision and update of the original authorís work.

A 6-year-old female was found by her mother to be playing in the yard when she suddenly felt pain in her left ankle. Her ankle became swollen, red, and painful. Her mother took her to the pediatrician's office. Upon careful examination there is a central puncture lesion with a small amount of serosanguinous drainage. No other examination findings are relevant. Her vitals are normal.

Questions to consider when evaluating this patient:
What are the potential causes for this lesion?
What immediate treatment is needed?
What advice should be given to the child and parents?

Many incidents of envenomations, bites and stings occur each year in the United States involving snakes, spiders, scorpions,other arthropods, and marine life. In Hawai'i, venomous snakes are not found although bites and stings from arthropods, spiders, scorpions, and marine life do occur. Patients may present for evaluation and treatment of confirmed or suspected envenomations most commonly in the emergency room or outpatient clinic setting. A clinician's careful assessment of the history, signs and symptoms is important in guiding the diagnosis and therapy.


Animal and human bites are fairly common. The clinical manifestations of infections can often be very serious. Bites occur in 4.7 million Americans yearly and account for 800,000 medical visits, including approximately 1% of all emergency department visits. The microbiology and infectious disease aspects of human, cat, and dog bites are bacteria associated with the environment, the victim's skin flora, or most important, the oral flora of the biter. In cats and dogs the most common bacteria is Pasteurella while in humans it's Staphylococcus, Streptococcus, and Eikenella. Routine wound care consists of wound irrigation to dilute bacterial counts and to cleanse the wound of foreign material. Irrigation solutions such as saline and tap water appear to be just as good as sterile antiseptic solutions. Cat bite wounds tend to be smaller and deeper, rendering these more infection prone than the larger and more open wounds from dog bites that can be more easily irrigated and cleansed. Commonly these do not undergo primary closure due to the concern of raising the risk of infection. First line treatment is with amoxicillin/clavulanic acid and penicillin allergic patients can be treated with clindamycin plus either ciprofloxacin, levofloxacin, or trimethoprim-sulfamethoxazole. Human bites generally have higher complication and infection rates than do animal bites. Infection may be determined based on the extent of tissue damage, depth of the wound and which compartments are entered. Bites to the hands tend to be fairly deep and frequently become infected. A fist to the teeth can result in a penetrating wound into the extensor tendon sheaths that appears small but is highly complication prone. Other considerations include immobilization of the affected area, including splinting if necessary, and elevation of the affected limb.


Snakes are responsible for many envenomations worldwide. There are thousands of species of snakes, although only about 15% of them are venomous. Venomous snakes, usually vipers (rattlesnakes, copperheads, cottonmouths, or water moccasins), bite approximately 8000 people in the United States yearly. Out of those 8000 people, 5 die, usually children or elderly who have delayed or no antivenom therapy. The highest numbers of deaths are reported in North Carolina, Texas, and Arkansas. Globally, there is estimated to be 1.2 million persons bitten by snakes each year. Not all bites by venomous species cause clinical effects. Many of the snakes found in the U.S are non-venomous or only mildly toxic species and these snakes are responsible for the majority of bites. Envenomation can cause extensive tissue destruction and devitalization that predisposes to infection from the snake's normal oral flora.

The largest family of venomous snakes is Viperidae, which includes the subfamily of Crotalinae, otherwise known as pit vipers (e.g., rattlesnakes, copperheads, and cottonmouths). Pit vipers may inflict "dry" bites, where a bite occurs without injection of venom.

The other venomous snake family is Elapidae, (e.g., cobras, coral snakes, and many species of Australian snakes). In this family the only snake indigenous to the United States is the coral snake. The coral snake has vivid bands of red, yellow, and black. A non-venomous snake commonly sold at pet shops has similar bands but in a different arrangement. A popular rhyme to identify the deadly coral snake found in the U.S. is, "Red on yellow, kills a fellow. Red on black, venom it lacks." This means that if red and yellow bands are adjacent to each other, this is a coral snake. But if red and black bands are adjacent to each other, this is a non-venomous snake.

Snakebites are often witnessed and it is most important to identify which type of snake caused the envenomation. Individuals may have different responses to specific venoms, and bites that appear to have caused minimal local effects may have very serious systemic consequences. The venom from the pit viper (family Viperidae) usually causes localized edema and pain that spreads proximally and after a few hours leads, to vesicular lesions and bullae, which are often hemorrhagic. The systemic sequelae include nausea, weakness, muscle fasiculations, changes in taste (metallic), and sensory changes. Envenomation by a coral snake (family Elapidae) classically presents first with ptosis and then progressive neuromuscular weakness including slurred speech, fasiculations, drowsiness, weakness, and respiratory failure. The venom blocks neuromuscular transmission at acetylcholine receptor sites. When death occurs in these cases, it is usually due to progressive paralysis of respiratory muscles.

Treatment of snakebites includes local wound care, which means washing the site, irrigation, providing analgesia, and resting the extremity. The affected extremity should be closely examined for edema and signs of compartment syndrome while also assessing the ABC's. Generally any patient who shows moderate to severe signs and symptoms after a venomous snakebite is a candidate for treatment. Poison information centers can provide information about antivenom availability and other management recommendations. In Hawai'i anti-venom is not needed because there are no venomous snakes in the environment.


Arthropods are animals without backbones and have at least a partly segmented body and stiff external skeleton. This is the largest group of organisms with more species than all other groups combined in both Hawai'i and the world. The class Arachnida includes spiders, mites, scorpions, and its relatives are all present in Hawai'i. Class Chilopoda includes centipedes with the rock centipede (family Lithobiidae) being native to Hawai'i. The scolopendra is the largest centipede reaching up to 12cm in length and is capable of inflicting a painful bite.

There are over 40,000 species of spiders that have been identified and many more are not yet classified in the world. Most bites cause minor and local skin irritation, which can lead to infection if not treated appropriately. In the United States, the black widow (Latrodectus spp.) and brown recluse (Loxosceles spp.) constitute the majority of medically significant envenomations. The black widow species is found throughout the U.S. and identified by their shiny black bodies and red markings, which resembles a red hourglass on their ventral aspect. The brown recluse spider (Loxosceles reclusa) inhabits the South and Midwest. They may be colloquially referred to as "fiddleback" or "violin" spiders due to the dark fiddle or violin shaped marking on their dorsal aspect.

Unlike snakebites, spider bites often are difficult to identify since puncture marks are uncommon and often the patient may not have felt a bite. It is important to recognize the toxidrome (signs and symptoms associated with a medically significant spider bite) and obtain a detailed history especially when suspicious of spider envenomation. The black widow is a non-aggressive spider, which bites in self-defense. Its neurotoxic venom initially causes local, radiating pain proximally to cause regional lymph node tenderness within the first 30 to 120 minutes. Its appearance might be target-like (concentric circls) but it is more often circular and red with a raised central area. Severe muscle cramping and spasms may occur because of neurotoxin acting at the presynaptic membrane causing the release and decreased uptake of acetylcholine. Dysautonomia manifested with nausea, emesis, sweating, hypertension, tachycardia, and malaise, can occur. The symptoms may last 36 to 72 hours. Treatment is supportive and includes analgesia and treatment of hypertension and tachycardia. Antivenom derived from horse serum is available but reserved only for the most severe cases due to the adverse effects and anaphylaxis that can occur from horse serum administration. Dantrolene treatment is often mentioned but it does not shorten the duration of symptoms.

Other types of spiders known to have necrotic venom are those found in the Sicariidae family, which includes both the brown recluse and six-eyed sand spiders. These bites can cause a central blister and develop into a necrotic center. Systemic reactions are infrequent and usually can be treated with supportive care. These symptoms can include fever, chills, arthralgias, nausea, and emesis. Very rarely, severe complications such as shock, renal failure, disseminated intravascular coagulation, and even death may occur.

Scorpions are related to spiders. They have four pairs of legs and a long curling tail with a stinger at the end. Scorpions primarily inhabit the Southwestern U.S. Most species are not dangerous to humans; however, the bark scorpion (C. exilicauda formerly sculpturatus) found in Arizona and New Mexico harbors a poisonous venom. Scorpions are found in Hawai'i but their venom is not significantly toxic. These envenomations tend to result in a simple painful and very localized reaction that can be treated supportively with analgesics and antihistamines. The more severe cases can result in neurologic compromise with respiratory and cardiovascular collapse.

In general, scorpions are not aggressive and tend to hide in crevices, under footboards, and burrow outside during the day to avoid the light. They are nocturnal creatures. Humans get stings to their hands and feet usually due to touching the scorpions in their hiding places.

Stings from the Arizona bark scorpion may require antivenom therapy if there are signs of systemic neurotoxicity. The antivenom currently lacks FDA approval and patients should be counseled regarding the risk of anaphylaxis and other potential side effects. The antivenom is only available in Arizona.

Arthropod stings more commonly occur from bees, wasps, ants and other arthropods. All of these arthropods contain mild venoms. Systemic allergic reactions occur more frequently from insect stings compared to insect bites in children. Stinging insects belonging to the order Hymenoptera (bees, wasp, and ants) are responsible for 40 to 50 deaths per year in the United States. Reactions to arthropod sting can be classified as usual, large local, anaphylactic, and toxic reactions. The usual arthropod sting causes local pain, swelling, and erythema, which resolves in a few hours. Large local reactions involve more extensive symptoms of extreme erythema and increased swelling to the site of the sting that continues to spread over 24 to 48 hours. Anaphylaxis is potentially life threatening and requires emergent treatment. Anaphylaxis is more common with envenomations by bees and wasps. Signs and symptoms include skin reactions in other parts of the body other than the site of envenomation, difficulty breathing, swelling of the tongue or throat, nausea, vomiting, signs of shock (lightheadedness, weak and thready pulse, hypotension). A toxic reaction occurs from envenomation from multiple stings due to an accumulation of the venom in the body. This can cause headache, vertigo, fainting, convulsion, fever, vomiting, and diarrhea.

The initial management is to remove the stinger. The stinger of the bee is barbed and detaches after being imbedded into the victim's skin. Since wasps can sting repeatedly, one may find grouped lesions without any visible stinger. The bee stinger contains venom sacs which if pinched can increase the level of envenomation. It is recommended to brush the stinger out of the skin. The usual and local reactions of insect stings require control of pain, pruritus, and swelling, as well as local wound care to prevent infections. Localized hypersensitivity reactions can be treated with topical corticosteroids and urticaria can be treated with antihistamines. Anaphylactic reactions are treated aggressively with injected epinephrine and other anaphlylaxis measures.

Repeat anaphylactic reactions to insect stings are more common in adults than in children. Children under 16 years old, who have isolated allergic reactions (urticaria and angioedema) after stings have a 10% incidence of subsequent systemic reactions and <0.1% incidence of a life threatening respiratory or cardiovascular allergic reaction. Children's sensitivity to insect venom is expected to diminish over time. An allergist should evaluate any child with an anaphylactic reaction to insect stings. Immunotherapy for insects can be used on children depending on the severity of the allergic reaction. Any child with a history of anaphylaxis and a positive skin test or in vitro assay for venom specific IgE could benefit from immunotherapy for 4 to 5 years. In children with large localized reactions who are at risk for future frequent or multiple stings, immunotherapy is an option. These children should also be given a self-administered epinephrine kit with instructions and a demonstration of its use. Patients should also obtain a medical alert bracelet.


Marine envonmations are very common in Hawai'i. They can occur from jellyfish, Portuguese man-of-war, and venomous fish. Jellyfish and Portuguese man-of-war envenomate using stinging cells called nematocysts that produce a protein-based venom. Stingrays have venomous spines on their long tails. As a general rule, these venoms tend to optimized for cold water and are thus heat labile and can be denatured with heat. These types of stings cause severe pain to the skin and can leave whip like erythematous welts that can last 24 to 72 hours after the initial insult. Most often the pain subsides quickly especially if application of hot water is used to the affected area for 15 to 30 minutes which is thought to the denature the protein-based venom. Commonly used treatments with vinegar and meat tenderizer (papain) are less effective than heat. More severe allergic reactions can cause fever, shock, and cardiopulmonary compromise, although this is extremely rare.

There are about 1,200 types of venomous fish, including lionfish, catfish, scorpionfish, weeverfish, toadfish, surgeonfish, rabbitfish, stargazers, and stonefish. They have spines on their dorsum that release the venom. In the case of the stonefish and possibly other types of venomous fish they may be stepped on and release venom into the victim's feet. They cause localized reactions similar to jellyfish and Portuguese man-of-war and can be treated using the application of hot water.


1. A ten-year-old male is stung by a bee. Upon examination of the sting site, a stinger is still embedded in the skin. What should you do?
. . . . . A. Pinch it off
. . . . . B. Brush it off
. . . . . C. Wait till you seek medical attention

2. A twelve-year-old male moving boxes in the basement experienced a pinprick sensation on his right hand followed by muscle cramps and swelling in his right axilla. On presentation to the ER a target lesion is noted on his right hand. The patient is noted to be nauseated, sweating, hypertensive, and tachycardic. What is the probably culprit?
. . . . . A. Centipede
. . . . . B. Scorpion
. . . . . C. Yellow jacket
. . . . . D. Black widow
. . . . . E. Brown violin spider

3. True/False: Ticks, flies and mosquitoes can cause anaphylaxis.

4. True/False: Repeat anaphylactic reactions to insect stings are more common in adults than in children.

5. What two spiders in the U.S. can inflict a serious and potentially deadly envenomation?

6. A teenage boy fishing is accidentally poked by a spiny fish. The site becomes red and painful. Which is NOT a reasonable step in the approach to management?
. . . . . A. Local wound care
. . . . . B. Epinephrine
. . . . . C. Application of heat to sting site
. . . . . D. Antibiotic ointment
. . . . . E. Tdap immunization
. . . . . F. Contact a poison information center


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5. Nishida GM, Tenorio JM. What Bit Me? Identifying Hawaii's Stinging and Biting Insects and Their Kin. 1993, Singapore: University of Hawaii Press.

6. Quan D. North American poisonous bites and stings. Crit Care Clin 2012; 28(4):633-659.

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Answers to questions

1. B

2. D

3. True, anaphylaxis can occur from any repeated insect bite or sting in which re-exposure to an antigen occurs.

4. True

5. Southern black widow and brown recluse spider.

6. B

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