Bites and Stings

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Chapter 63 Bites and Stings

Kate M. Cronan, MD, FAAP

1 True or false: Bites from imported fire ants (Solenopsis invicta) can cause severe systemic reactions

True. Local reactions can consist of a wheal, a pustule, or a large local reaction. Systemic reactions may range from urticaria to life-threatening anaphylaxis.

deShazo RD, Williams DF, Goddard J, et al: Medical consequences of stings of imported fire ants, 2006: www.uptodate.com

2 Describe the bite of the imported fire ant. How is it treated?

Imported fire ants are nonwinged hymenoptera found in the Southeastern and South Central United States. They bite with their jaws, then pivot around and sting at multiple sites in a circular pattern. Within 24 hours a sterile pustule develops at the site of the stings. This lesion can be diagnostic of a fire ant sting. Stings often occur on the legs and feet of children. Treatment consists of local wound care, antihistamines, and steroids for severe cases.

Hodge D, Tecklenburg F: Imported fire ants. In Fleisher G, Ludwig S, Henretig F (eds): The Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins, 2006, p 1053.

3 What are the common microbiological organisms of dog, cat, and human bites?

Dog bites: Staphylococcus aureus, streptococci, Pasteurella canis

Cat bites: Pasteurella multocida, Staphylococcus aureus, streptococci

Human bites: Streptococcus viridans, Staphylococcus aureus, anaerobes, Eikenella corrodens

Talan DA, Citron DM, Abrahamian FM, et al: Bacteriologic analysis of dog and cat bites. N Engl J Med 340:85, 1999.

5 How can one tell if a human bite was inflicted by an adult or a child?

If the intercanine distance is greater than 3 cm, it is most likely caused by an adult. This should raise concerns about child abuse.

American Academy of Pediatrics. Committee on Child Abuse and Neglect. American Academy of Pediatric Dentistry. Ad Hoc Work Group on Child Abuse and Neglect: Oral and dental aspects of child abuse and neglect. Pediatrics. 104:348–350, 1999.

6 What is the preferred hand position for evaluation of a fist injury from a bite?

Evaluate the wounds when the hand is in a clenched position. This permits more accurate assessment of the injuries. Once the hand is relaxed, it is difficult to assess the extent of injury because the deeper tissues form a closed space permitting the growth of bacteria.

7 What causes rat-bite fever?

Rat-bite fever is caused by one of two organisms: Streptobacillus moniliformis or Spirillum minus. Mice, squirrels, cats, and weasels can also carry these organisms. Transmission to humans occurs via bites, scratches, handling infected rats, or ingestion of food or water contaminated by rat excreta.

American Academy of Pediatrics: Red Book 2006: Report of the Committee on Infectious Diseases; 27th ed. Elk Grove, IL, American Academy of Pediatrics, 2006, p 559.

8 How does rat-bite fever present?

Exposure to either organism results in abrupt onset of fever, chills, myalgia, extremity rash, and headache. The rash usually begins as a maculopapular eruption and often involves the palms and soles. With Streptobacillus moniliformis infection, the rat bite heals quickly and is followed by migratory polyarthritis in approximately 50% of patients. Pneumonia, endocarditis, myocarditis, and meningitis may occur. With Spirillum minus infection, the bite heals and is followed by local ulceration, lymphangitis, and lymphadenopathy. Occasionally arthritis also develops.

Fatal rat-bite fever—Florida and Washington, 2003. MMWR Morb Mortal Wkly Rep 53:1198–1202, 2005.

9 What is the best multipurpose insect repellent?

DEET (N,N-diethyl-m-toluamide) is the best multipurpose insect repellent. DEET is the active ingredient in most commercial insect repellents. It is available in various forms, including sprays, gels, liquids, and sticks, and in concentrations of 4–100%. DEET can be applied to skin or clothes. It should not be applied under clothes. It does not work against stinging insects but is quite effective against mosquitoes, gnats, chiggers, ticks, and other insects. DEET washes off with water and perspiration. It is important to note that application of DEET may reduce the efficacy of sunscreen.

10 What are the major disadvantages of DEET?

DEET can be toxic, and use of low concentrations (10%) is recommended in children. It should be applied to the clothes more than to the skin. Application to areas around the eyes, mouth, and open skin lesions should be avoided. For children, DEET should be applied once per day. It should be avoided completely for children younger than 2 months of age. Oral ingestion of large quantities of DEET may cause seizures, coma, or death. For those concerned about the possible toxicity of DEET, citronella, a plant-derived insect repellent, is a good alternative.

Fradin MS, Day JF: Comparative efficacy of insect repellents against mosquito bites. N Engl J Med 347:13–18, 2002.

11 What is papular urticaria?

Papular urticaria is a skin condition that consists of intensely pruritic wheals and papules. These lesions are attributable to arthropod bites in specifically sensitized children. Sensitization may occur in infancy, but the lesions do not appear until the second year of life in many cases. Various arthropods have been identified as culprits: dog lice, mosquitoes, bedbugs, fleas, mites, and chiggers. The wheals represent an immediate hypersensitivity reaction to insect bites. Wheals then evolve into papules, which represent a delayed hypersensitivity reaction. New lesions form continually, and the eruption may persist for many months. The lesions usually appear on exposed areas, such as the extremities, head, neck, and shoulders. The differential diagnosis includes scabies, varicella, pediculosis, urticaria, and insect bites without papular urticaria.

12 How is papular urticaria treated?

Treatment should focus on an multipurpose insecticide for the entire home. Household pets should be included in the treatment. When the cause of the lesions is removed, clinical symptoms should improve greatly, but supportive treatment is necessary. Oral antihistamines and topical steroid creams help to control the itching.

13 Name the tick-borne infectious diseases that occur in the United States

Bacterial: Lyme disease, tularemia, relapsing fever

Rickettsial: Rocky Mountain spotted fever, ehrlichiosis

Viral: Colorado tick fever

Protozoal: Babesiosis

American Academy of Pediatrics: Red Book 2006: Report of the Committee on Infectious Diseases, 27th ed. Elk Grove, IL, American Academy of Pediatrics, 2006, p 195.

14 In penicillin-allergic patients who present with a human bite or a high-risk animal bite, what antibiotic regimen is recommended?

Prophylaxis and treatment for penicillin-allergic children are challenging problems. Erythromycin and tetracycline activity against Staphylococcus aureus and anaerobes is unreliable. Tetracycline is effective against Pasteurella sp., but the risk of dental staining in children younger than 8 years must be considered. Therefore, combination treatment with oral or parenteral trimethoprim-sulfamethoxazole (effective against Staphylococcus aureus, Eikenella corrodens, and Pasteurella sp.) and clindamycin (effective against anaerobes, streptococci, and Staphylococcus aureus) may be effective for preventing or treating bite wound infections. Ceftriaxone may be used if the patient can tolerate cephalosporins. Metronidazole provides excellent anaerobic coverage and may be used as an alternative to clindamycin.

American Academy of Pediatrics: Red Book 2006: Report of the Committee on Infectious Diseases; 27th ed. Elk Grove, IL, American Academy of Pediatrics, 2006, p 195.

15 Define Hymenoptera sting

A sting consists of an injection of venom via a tapered shaft that projects from the venom sac located in the abdomen of females of the Hymenoptera species. Stings usually occur in warm weather.

16 Which group of the order Hymenoptera is considered aggressive—apids or vespids?

Bees, wasps, and hornets are responsible for many of the anaphylactic reactions to venomous insects in the United States. Apids include honeybees and bumblebees; vespids include yellow jackets, hornets, and wasps. Apids tend to be docile and sting only when provoked. The bumblebee is large, slow-moving, and very noisy. Honeybees may cause problems among beekeepers. Vespids are aggressive; the yellow jacket is the most aggressive in this family. Yellow jackets are thought to be the principal cause of allergic reactions to insect stings in the United States.

17 How are reactions to bee stings categorized?

The most common reaction is a small local reaction that presents as a painful pruritic lesion < 5 cm at the site of the sting and lasts briefly (several hours).

A large local reaction occurs in approximately 10% of people after a sting and manifests with swelling and erythema in the area of the sting. It is usually > 5 cm in diameter, often very painful and itchy, and lasts for > 24 hours, sometimes up to 1 week. The features of this reaction may be confused with cellulitis, but cellulitis rarely develops after a bee sting.

Systemic reactions, which occur in approximately 0.5% of Hymenoptera stings, begin within minutes to hours after the sting and can be mild or severe.

Mild systemic reactions most commonly consist of dermal signs and symptoms: generalized urticaria, pruritus, flushing, and angioedema. Gastrointestinal symptoms, such as abdominal pain, nausea, and diarrhea, may also occur.

Severe systemic reactions include life-threatening signs, such as upper airway edema with hoarseness and stridor; shock, manifested by pallor and fainting; and bronchospasm, characterized by coughing, dyspnea, and wheezing.

Unusual reactions to bee stings include vasculitis, nephrosis, encephalitis, and serum sickness. Symptoms usually occur several days to several weeks after the sting and tend to last for a long time.

18 What is the best way to remove a stinger from a bee sting?

If a stinger remains in the skin after a bee sting, it should be swiped sideways away from the direction in which it points. A credit card or other similar card works well to do the swiping. Grasping and pulling the stinger may squeeze the remaining venom from the venom sac into the sting site. The stinger should be removed as soon as possible to avoid further deposition of venom.

19 What is the treatment for anaphylaxis due to an insect sting?

The treatment is the same as for anaphylaxis from other causes. Attention must be paid first to airway, breathing, and circulation. Intramuscular epinephrine in a 1:1000 dilution should be given immediately; the dose may be repeated every 30 minutes as needed. Intravenous epinephrine is rarely indicated except in the case of profound shock. Antihistamines, such as diphenhydramine or hydroxyzine, given parenterally, may reduce urticaria and pruritus. Steroids, such as methylprednisolone, should be administered early in the treatment plan. Depending on the severity of the reaction, other treatment modalities may be indicated (vasopressors, supplemental oxygen, IV fluids, bronchodilators).

After recovery, emergency kits for self-administration of epinephrine should be prescribed. Detailed instructions about technique and appropriate use must be provided to the patient and family.

Vankawala H, Park R: Bee and Hymenoptera stings: www.emedicine.com/emerg/topic55.htm

20 What is the significance of the Southwestern desert scorpion, Centruroides exilicaida?

It is the only scorpion species of medical importance in the United States. Also called the Arizona bark scorpion, it is found mainly in Arizona, Texas, and California. Arizona bark scorpions are yellow or brown and are usually 5 cm in length. Their appearance resembles that of the shrimp. Their long, very mobile tails contain the stinger. They tend to reside in brush areas and trees and sting mostly at night. Children are usually stung on their extremities.

21 How does the venom of the Arizona bark scorpion work?

The venom is mostly neurotoxic. It overstimulates the parasympathetic and sympathetic nervous systems and results in agitation, tachycardia or bradycardia, hypertension, dysrhythmias, and increased secretions. Cranial nerve dysfunction may cause rapid dysconjugate eye movements and contractions of muscles of the face and tongue. Peripheral motor neuron involvement presents as muscle contractions and uncontrolled jerking movements of the extremities, which may be mistaken for seizures. Respiratory distress may result from decreased pharyngeal tone and uncoordinated contraction of respiratory muscles.

22 How are scorpion envenomations treated?

Treatment of scorpion envenomation is usually supportive; focus must be placed on airway control. Local wound care should be provided along with tetanus prophylaxis. Children with systemic signs and symptoms should be admitted to the hospital. Analgesics and benzodiazepines should be administered for pain and agitation. Many authorities prefer a continuous infusion of midazolam. A hyperimmune goat serum antivenin is known to be effective but has not been approved by the Food and Drug Administration. It is therefore available only in Arizona, where the Arizona State Board of Pharmacy has approved its use.

Bush S, Gerardo C: Scorpion envenomations: www.emedicine.com/emerg/topic524.htm

23 What are the four kinds of sharks in the United States that are responsible for most shark bites?

Gray reef, great white, blue, and mako sharks. Bites from these sharks can cause extensive injury, including fractures, amputations, and penetration of internal organs.

Hodge D, Tecklenburg FW: Bites and stings. In Fleisher GR, Ludwig S, Henretig FM (eds): Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins, 2006, p 1045.

24 Which two spiders in the United States cause significant envenomations?

The black widow spider (Latrodectus mactans) and the brown recluse spider (Loxosceles reclusa) are the only two spiders known to cause significant envenomations. Brown recluse spider bites occur much more frequently than black widow spider bites. Brown recluse spiders are nonaggressive and usually bite only when threatened. They have a brown or yellow violin-shaped marking on the dorsal thorax and are found most commonly in the Southern and Midwestern states. They prefer dark, warm, protected areas, such as closets and garages. Black widow spiders inhabit all states except Alaska and are found most commonly in the South, Ohio Valley, Southwest, and West Coast. They are found in attics, barns, trash piles, and other dimly lit areas. Bites are more frequent in the warmer months. The black widow spider is jet black, with an hourglass-shaped red mark on the underside of the abdomen.

25 What are the symptoms of the bite of a brown recluse spider?

At the time of the bite, a stinging sensation may be felt. Increased pain and pruritus may develop within several hours. The clinical course ranges from mild local irritation to large necrotic skin lesions and systemic reactions. Most bites go unnoticed or result in only a mild red papule that heals quickly. A central vesicle with surrounding erythema is discovered at the site of the bite. In some scenarios, vasospasm and hemorrhage in the first few hours after the bite account for the red, white, and blue discoloration. Systemic signs and symptoms occur in approximately 40% of envenomations, including fever, nausea, vomiting, headache, and arthralgias. A scarlatiniform rash may occur simultaneously. Systemic loxoscelism is rare and seen almost exclusively in children. It is characterized by anemia, hemolysis and thrombocytopenia, shock, and renal failure.

26 How is the bite of a brown recluse spider treated?

Treatment consists of local wound care; extensive dermal injury may require skin grafting. Analgesics and tetanus immunization are mainstays of therapy. If extensive intravascular hemolysis occurs, it is crucial to maintain high urinary flow rates with alkalinization of the urine via sodium bicarbonate infusion.

Stibich A, Schwartz R: www.emedicine.com/DERM/topic598.htm

27 What is latrodectism?

This term applies to systemic symptoms due to the spread of the neurotoxin from black widow spider bites. There are three phases of latrodectism:

The exacerbation phase, which occurs from < 6 up to 24 hours and is characterized by muscle spasms at the site of the bite or elsewhere

The dissipation phase, which occurs 1–3 days after the bite and is a time when symptoms subside

The residual phase, which occurs weeks to months after the bite and may consist of persistent tremors and weakness and fatigue

Castells M: Spider bites: www.uptodate.com

28 How is the bite of a black widow spider treated?

Treatment consists of analgesia, including oral narcotics for milder cases and IV morphine for more severe cases. Benzodiazepines can relieve anxiety. An antivenin is available, but it is indicated only for the most severe cases unresponsive to the above measures. Life-threatening tachycardia and hypertension are indications for this antivenin. Death is extremely uncommon.

29 What infectious agent should be considered when treating an iguana bite?

Iguanas are becoming popular pets. They can inflict injury via scratching, biting, and tail whipping. They frequently carry unusual subtypes of fecal salmonella. The Centers for Disease Control and Prevention recommends that children under age 5 and those who are immunocompromised should not have iguanas and other salmonella-carrying pets, such as turtles, in the home.

Reptile-associated salmonellosis—selected states, 1998–2002. MMWR Morb Mortal Wkly Rep 52:1206–1209, 2003.

30 What are the poisonous snakes indigenous to the United States?

Snakes in the Crotalidae family (pit viper) family and Elapidae family (coral snakes) are poisonous. Rattlesnakes, copperheads, and water moccasins are pit vipers and account for 99% of poisonous snakebites. The coral snake accounts for less than 1% of poisonous snakebites.

31 How can pit vipers be distinguished from nonpoisonous snakes?

Pit vipers have two pits, one on either side of their head, and their pupils are elliptical and vertically oriented. The head is triangular and they have two curved fangs that are widely spaced. The scales caudal to the anal plate continue in a single row. Nonpoisonous snakes have oval heads with round pupils. The anal plate has a double row of subcaudal plates.

Hodge D, Tecklenberg F: Snake bites. In Fleisher G, Ludwig S, Henretig F (eds): The Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott, Williams & Wilkins, 2006, p 1054.

32 What causes tularemia?

Francisella tularensis, a gram-negative pleomorphic coccobacillus, is the causative agent. Sources of this organism include many species of wild mammals, some domestic animals (e.g., sheep, cattle, cats), and the blood-sucking arthropods that bite these animals (e.g., ticks and mosquitoes). In the United States, rabbits and ticks are major sources of infection.

American Academy of Pediatrics: Red Book 2006: Report of the Committee on Infectious Diseases, 27th ed. Elk Grove, IL, American Academy of Pediatrics, 2006, p 705.

33 How does tularemia present? How is it treated?

Most patients present with an abrupt onset of fever, chills, myalgia, and headache. There are several tularemic syndromes. The most common is the ulceroglandular syndrome, which presents with a painful maculopapular lesion at the bite site and painful, acutely inflamed lymph nodes. Other less common syndromes are the glandular, oropharyngeal, oculoglandular typhoidal, intestinal, and pneumonic presentations.

The treatment is streptomycin. Gentamycin is an effective alternative.

American Academy of Pediatrics: Red Book 2006: Report of the Committee on Infectious Diseases, 27th ed. Elk Grove, IL, American Academy of Pediatrics, 2006, p 706.

34 How soon after an exposure should immunoprophylaxis for rabies begin?

After thorough wound care is completed, passive and active immunoprophylaxis is required for optimal therapy. Begin prophylaxis as soon as possible after exposure, ideally within 24 hours. However, a delay of several days or more may not compromise effectiveness; begin prophylaxis, if indicated, regardless of the time of exposure.

American Academy of Pediatrics: Red Book 2006: Report of the Committee on Infectious Diseases, 27th ed. Elk Grove, IL, American Academy of Pediatrics, 2006, p 556.

35 Which type of jellyfish sting is highly toxic?

Stings from the common purple jellyfish (Pelagia noctiluca) and the sea nettle jellyfish (Chrysaora quinquecirrha) are only mildly toxic. Local skin irritation is the usual clinical manifestation. However, stings from lion’s mane(Cyanea capillata) are highly toxic. This jellyfish is found along both coasts of the United States. Contact with the tentacles of lion’s mane causes severe burning; prolonged exposure results in muscle cramps, and respiratory failure may ensue.

36 How are toxic jellyfish stings treated?

Treatment of toxic jellyfish stings focuses on relieving pain, alleviating effects of the venom, and supportive therapy. The first goal is to remove the tentacles to avoid further nematocyst discharging. It is possible to inactivate the remaining nematocysts by topical application of vinegar (acetic acid) for 30 minutes. Alternative solutions include baking soda slurry or meat tenderizer. The sting area should be washed with normal saline or sea water. The residual tentacles should be removed with instruments or gloved hands. No antivenin is available. Antihistamines, steroids, and analgesics may be indicated. Cardiac and respiratory support may be required.

37 How should one remove a tick embedded in the skin?

Grasp the tick by the head or the mouth with blunt angled forceps as close to the skin as possible. This action should be perpendicular to the patient’s skin. With steady traction, pull the tick and do not twist as you pull back. It is best not to squeeze, puncture, or crush the tick as it could regurgitate material into the wound during removal. If any residual parts or cement is noted on the skin, remove it with forceps. Alternatively, use a large-gauge needle to swipe residual parts away. Cleanse the bite wound after removal. Do not apply petroleum jelly, a hot match, alcohol, or other irritants.

Howard J, Loiselle J: A clinician’s guide to safe and effective tick removal. Contemp Pediatr 23:36–42, 2006.

38 How important is the duration of attachment of ticks to the skin?

Duration of attachment to the host plays a major role in the transmission of pathogens. Borrelia burgdorferi from an infected tick has a higher likelihood of transmission after 24 hours, and this likelihood increases after 72 hours. On the other hand, Ehrlichia chaffeensis requires a shorter period for transmission.

Howard J, Loiselle J: A clinician’s guide to safe and effective tick removal. Contemp Pediatr 23:36–42, 2006.

39 What are the most effective precautions to avoid Lyme disease?

Personal protection consists of wearing appropriate clothes: Wear long sleeves and long pants in at-risk areas.

Use of repellants: DEET applied to the skin and clothes. Consider the use of Permethrin applied to the clothes in conjunction with DEET.

Inspection: Parents should inspect their children after times spent in risky areas. If a tick is found on the skin, washing can be effective before attachment occurs.

Modification of outdoor environment: Replace brush with wood chips.

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