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?

image Dog bites: Staphylococcus aureus, streptococci, Pasteurella canis

image Cat bites: Pasteurella multocida, Staphylococcus aureus, streptococci

image 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.

4 Which bites should be routinely treated with prophylactic antibiotics?

image All dog bites involving hands and feet

image All human bites

image All cat bites

image Puncture wounds

image Bites for which treatment has been delayed for more than 24 hours

image Bites in immunosuppressed patients

KEY POINTS: BITES THAT SHOULD NOT BE SUTURED

1 Puncture wounds

2 Bites on the hands

3 Cat bites

4 Human bites

5 Crush injuries

6 Dog bites with delayed presentation

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

image Bacterial: Lyme disease, tularemia, relapsing fever

image Rickettsial: Rocky Mountain spotted fever, ehrlichiosis

image Viral: Colorado tick fever

image 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.

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