Sting and Bite Injuries Case File

Sting and Bite Injuries Case File

Eugene C. Toy MD, Donald Briscoe, MD, FA  AFP, Bruce Britton, MD, Joel J. Heidelbaugh, MD, FA  AFP, FACG

Case 43

The mother of a 16-year-old adolescent girl calls you when you are on call on a Saturday afternoon. The mother states that her daughter was either stung by a bee or bitten by a spider on her left arm several hours ago. The patient has no known history of previous allergic reactions to insect bites or stings. She is having no difficulty breathing or swallowing, nor has she been dizzy or light-headed. The mother's primary concern is that the area around the bite or sting is red and swollen. She says that the site of the injury was the midpoint of the forearm, and now it hurts, slightly itches, and there is redness and swelling extending in a circular pattern several centimeters in diameter. The red area is moderately warm to the touch, so her mother is concerned that it is infected. She gave her daughter some ibuprofen for the pain and would like you to phone in a prescription for an antibiotic as well as something to prevent the reaction from spreading.

⯈ What is the most appropriate first step in treatment of this patient?

⯈ What other treatments might be beneficial at this point?

⯈ What immunization is appropriate for this patient?

ANSWER TO CASE 43:

Sting and Bite Injuries

Summary: A 16-year-old adolescent girl has been stung by a wasp and is having a painful and itchy local reaction. Also included in the differential diagnosis for this case are nonvenomous insect bites ( eg, mosquito) and spider bites. She has no history of previous allergic reactions. The patient's mother is calling and asking you to manage the situation over the phone by prescribing antibiotics.

• Most appropriate antibiotic to use: No antibiotic treatment is indicated, as this is a local reaction to a bee sting, with high likelihood for a histamine-mediated reaction, and a low likelihood of a bacterial infection.
• Next step in therapy: Local application of ice, oral administration of nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen for pain, and oral or topical antihistamines for itching.
• Immunization that is appropriate: Tetanus-diphtheria-pertussis (Tdap) booster, if not up-to-date.

ANALYSIS

Objectives

1. Know the insects that commonly cause bite and sting injuries.
2. Be able to differentiate local from systemic reactions to bites and stings.
3. Know the management of common insect bite and sting as well as animal bite injuries.

Considerations

This adolescent without a history of allergies has sustained a wasp sting, and no therapy is required other than symptomatic treatment. The insect order Hymenoptera includes wasps, yellow jackets, hornets, honeybees, bumblebees, and fire ants. These insects cause the majority of cases of sting- or bite-induced anaphylaxis and cause more mortality than all other types of insect bites and stings. Local reactions occur as a result of the toxic properties of the venom, whereas more severe reactions tend to be caused by allergic reaction to venom allergens.

Several types of bee stings result in the retention of the stinger in the victim, which can result in continued injection of the bee venom. Stingers should be promptly removed with caution, as grasping the base of the stinger may result in compression of a venom-containing sac, resulting in increased venom release. Thus, it is suggested that scraping or brushing the stinger off of the skin is preferable to grasping the stinger. However, rapidly removing the stinger is preferable to taking the time to locate a scraping implement if one (such as a credit card or driver's license) is not immediately at hand.

Spider bites may present in the same fashion as many insect and bee stings. Typically, the development of pruritus and histamine-mediated swelling within the first few hours of the bite are absent. Cellulitis is common, as is the development of an eschar at the site of the bite. Most spider bites, especially those associated with the brown recluse spider, are associated with methicillin-resistant Staphylococcus aureus (MRSA).

Approach To:

Bites and Stings

DEFINITIONS

HYMENOPTERA: Order of insects which includes wasps, yellow jackets, hornets, honeybees, bumblebees, and fire ants, and make up the majority of insect stings.

LARGE LOCAL ALLERGIC REACTIONS: Erythema and warmth of the skin at the area of insect sting, mediated by immunoglobulin E (IgE) reactive to the Hymenoptera venom.

CLINICAL APPROACH

INSECT STINGS AND BITES

Local Reactions

Almost all Hymenoptera stings will result in a local reaction, which includes redness, swelling, pain, and itching at the site of the injury. These reactions tend to occur almost immediately and last for hours to days. The local tissue response is a consequence of a histamine-mediated reaction caused by the venom that is released by the sting. Local reactions can be treated with ice and antihistamines for itching. Tetanus prophylaxis should be provided for those who have not been vaccinated.

Delayed Reactions

Large local allergic reactions are mediated by IgE reactive to the Hymenoptera venom. These reactions are often confused with cellulitis, as large areas ( >10 cm in diameter) of redness and warmth develop over 24 to 48 hours. These reactions are not infectious and will not respond to antibiotics. These reactions are best treated with oral steroids initiated early after the sting, as these reactions may last up to 5 to 10 days. Tetanus prophylaxis should be reviewed and updated if necessary. A person with a history of a large local reaction to a bee sting is likely to have similar reactions to subsequent stings. However, the history of this type of reaction does not result in an increased risk of anaphylaxis to subsequent stings.

Anaphylaxis

Up to 4% of the population may have a systemic reaction to a Hymenoptera sting. Those who have had a previous systemic reaction have a 50% or greater risk of having a systemic reaction to future stings. These systemic reactions can vary from milder symptoms of nausea, generalized urticaria, or angioedema to severe and life-threatening hypotension, shock, airway edema, and death. Severe immediate hypersensitivity reactions usually occur within minutes of the sting.

Treatment of anaphylaxis should include assessment and management of the ABCs (airway, breathing, and circulation), with intubation if necessary, IV access, and fluid resuscitation at 10 to 20 mg/kg (usually 500-1000 cc) as soon as possible. Subcutaneous or intramuscular epinephrine should be administered as quickly as possible (0.3-0.5 mL of 1:1000 solution for adults; 0.01 mg/kg for children at 0.3 mg maximum dose) and repeated in 5 to 10 minutes if needed. Antihistamines, steroids (if severe), and bronchodilators may be required as well. Anyone with an anaphylactic reaction should be observed in a hospital setting for 12 to 24 hours, as the symptoms can recur. Persons with known anaphylactic reactions should be prescribed epinephrine injector kits to carry with them for immediate access at all times. They should be instructed to avoid wearing perfumes, bright clothing, and avoid walking barefoot when in areas prevalent with bees. Desensitization therapy can also be offered to those with known anaphylaxis, as their risk of future severe reactions can be reduced by up to 50%.

Most spider bites do not cause significant injury or illness. When suspected, the area should be cleansed with warm soap and water, and a cool compress should be applied to the affected area. NSAIDs or acetaminophen are also recommended. When erythema, warmth, and pain develop around the site of injection, MRSA cellulitis should be considered, and the patient should be treated with either oral clindamycin or trimethoprim-sulfamethoxazole. If oral antibiotics do not adequately treat the cellulitis, abscess should be considered and if present, incision and drainage should be performed. In these cases, as well as for those resistant to oral antibiotics, intravenous vancomycin should be started.

ANIMAL BITES

Nearly 5 million animal bites occur in the United States each year. The most common animals involved are dogs and cats, while human bites are also common. Cat and rodent bites are notorious for being "injection" -type bites, while those from dogs and humans are commonly "crush" -type bites, based on the teeth involved in the bite.

The initial management of the patient who has been bitten should focus on the ABCs and on protection of the current injury ( eg, splinting of fractures, protection of cervical spine, etc), as well as local wound care including control of bleeding and assessment of the injuries incurred. History should be gathered on the type of animal that caused the bite, the situation regarding the bite (whether provoked or unprovoked), and the vaccination status of the animal, particularly to document rabies vaccination status. Almost all cases of human rabies in the United States since 1960 have been caused by bats, skunks, dogs, foxes, and raccoons. Consultation with your local health department after animal bites is recommended.

Local cleaning of the wound(s) with soap and water, irrigation with sterile saline solution, and debridement of devitalhed tissue should take place as soon as possible. For minor and superficial to shallow wounds, these treatments are often all that is required.

The risk of infection from an animal or human is dependent on numerous factors. Larger and deeper wounds are more likely to become infected than smaller, superficial wounds. Bite wounds on the hand tend to have an increased risk of infection due to thin skin and close proximity to small joint spaces. Host factors, such as the presence of chronic illnesses or immune suppression, also play a role in susceptibility to infection. Cat and human bites have a high risk of infection and should always be treated empirically with antibiotics, whereas only 20% of dog-bite wounds become infected.

Many different bacteria can be involved in bite wound infections. All cat bite wounds should be suspected to be contaminated with Pasteurella multocida. Both cats and dogs carry multiple species of staphylococci and streptococci, as well as anaerobic bacteria. Humans carry staphylococci, streptococci, Haemophilus species, Eikenella species, and anaerobic bacteria.

The treatment of bite wounds starts with local care-cleaning, irrigation, and debridement of crushed and infected tissue. The primary closure of bite wounds is controversial and should be limited to lacerations less than 12 hours old. Deep puncture and wounds with signs of infection should be well irrigated with sterile solution and not primarily closed. Tetanus vaccination should be updated in all patients as needed. Hepatitis B and HIV postexposure prophylaxis should be considered for patients who sustained a human bite from a high-risk person. Animal control authorities should be contacted for guidance regarding rabies vaccination.

All patients who sustained cat bites should be treated for 10 to 14 days with oral amoxicillin-clavulanate. Although clear evidence of efficacy is lacking for the treatment of dog and human bites, current recommendations are for antibiotic prophylaxis with amoxicillin-clavulanate for 5 to 7 days for patients with moderate-to-severe wounds. When cellulitis is present, longer courses of antibiotic therapy, usually 10 to 14 days, are required. Hospitalization, intravenous antibiotics, and surgical intervention may be required for more severe infections including osteomyelitis, septic joint infections, and in patients with complicating medical conditions including immunosuppression.

COMPREHENSION QUESTIONS

43.1 Which of the following therapeutic options is recommended in treating both bee stings and bite wounds?

A. Antibiotic prophylaxis with amoxicillin-clavulanate

B. Antihistamines for itching

C. Tetanus vaccination

D. Surgical wound debridement

43.2 A 22-year-old woman develops a progressively enlarging red, hot area on her leg following a sting from a yellow jacket. She states that the sting was sharp and of brief duration and she was able to fully remove the stinger with tweezers. She did not suffer any symptoms of systemic anaphylaxis. She has no previously known allergies. She sees you in the office a day after the sting and states that the area of the sting is still enlarging despite using over-the counter corticosteroid cream and a first-generation antihistamine. Which of the following is the most appropriate next treatment for this patient?

A. Oral prednisone

B. Topical corticosteroid

C. Antibiotic directed against gram-positive cocci

D. Portable epinephrine kit for future stings

E. Reassurance

43.3 You see a 7-year-old boy a day after he was bitten by his pet dog. According to his mother, the dog bit the child after he surprised the dog and grabbed its tail. The dog has had all of its vaccinations, including rabies. The child has had no fever, has full movement of the injured limb, and has no sign of neurologic or vascular injury. The wound is on the child's forearm, is not deep, is not bleeding, but has developed 2 cm of erythema surrounding the site. Which of the following is the most appropriate treatment?

A. Hospitalization for IV antibiotic

B. Oral amoxicillin-clavulanate for 3 to 5 days

C. Oral amoxicillin-clavulanate for 7 to 14 days

D. Local care without any antibiotic

43.4 You see a 43-year-old man who was involved in a fist fight 2 days ago and

sustained a deep laceration wound around his knuckles from where he struck

the face of another man. He was intoxicated at the time and upon return

home, he did not clean the wound and went straight to sleep. The injury site

has now developed purulent drainage, pain, erythema, and the man has a

low-grade fever. There is no rash and he has not noted any spreading of the

erythema. An x-ray of the hand shows a hairline fracture of the fifth metacarpal

head with swelling and bruising noted over the affected area. Which of

the following is the most likely organism causing infection?

A. Methicillin-resistant S aureus

B. Streptococci

C. Eikenella corrodens

D. Escherichia coli

E. Peptostreptococcus

43.5 A mother brings in her 6-year-old child who was bitten on the hand while playing with a rabbit that was recently obtained from a neighbor. The child's wound is on the volar surface of the right second finger just distal to the proximal interphalangeal joint. Which of the following steps in the management of bite wounds is most effective in preventing wound infection?

A. Tetanus prophylaxis

B. Rabies prophylaxis

C. Saline irrigation and wound care

D. Prophylactic antibiotics

E. Irrigation and primary closure

ANSWERS

43.1 C. Tetanus vaccination is common to the management of both bee stings and bite wounds. Bee stings rarely become infected and do not require antibiotic therapy.

43.2 A. This patient is having a large, local reaction to her sting. This is an IgE mediated reaction. It may respond to a course of oral steroids. There is at least a 50% chance that a similar reaction will occur if she was stung again, but she is unlikely to develop anaphylactic reactions in the future and does not need anaphylaxis prophylaxis. The patient should be informed that the localized reaction may take 5 to 10 days to completely resolve, and may resolve more quickly with treatment with oral steroids. Her history of a sting makes cellulitis less likely.

43.3 C. This child is developing cellulitis from the bite wound. Based on his presentation, he does not appear to require hospitalization. He can be treated with oral antibiotics for 1 to 2 weeks.

43.4 C. While each of these bacteria can be isolated in injuries from human bites, Eikenella species appear to be most common in closed fist injuries. For patients presenting after a "fist fight" with bite injuries, prophylaxis with amoxicillin-clavulanate is indicated due to inoculation with oral flora into the skin and subcutaneous tissues.

43.5 C. Rodents and lagomorphs (rabbits) are neither reservoirs of the rabies virus nor have been shown to transmit the rabies virus to humans. The most important step in preventing the infectious complications of bite wounds is proper wound care with inspection, irrigation, and debridement. Tetanus prophylaxis should be considered in all bite wounds. Antibiotic prophylaxis may also be indicated especially in high-risk bites (those located on the hand, late presentation, cat bites) and should be directed against staphylococci, streptococci, anaerobes, and Pasteurella species as appropriate.

CLINICAL PEARLS

⯈ Anyone with a history of anaphylactic reactions should be given a prescription for an epinephrine injector kit and instructed in the importance of keeping it at hand. These prescriptions need to be updated often, as the medication expires in 6 to 12 months .

⯈ Local cleaning of the wound(s) with soap and water, irrigation with saline, and debridement of devitalized tissue should take place as soon as possible.

⯈ Human "bite" wounds are not always the result of a bite. A punch to the mouth can cause a serious inoculation and infection to the knuckles of the puncher .

⯈ All cat and human bites should be empirically treated with amoxicillinclavulanate due to high rates of infection, whereas approximately 20% of dog-bite wounds become infected.

⯈ Cellulitis following spider bites should be treated with the suspicion of MRSA with oral clindamycin ortrimethoprim-sulfamethoxazole.

REFERENCES

Brook I. Management of human and animal bite wounds: an overview. Adv Skin Wound Care. 2005; 18(4):197-203. 

Chen E, Hornig S, Shepherd SM, Hollander JE. Primary closure of mammalian bites. Acad Emerg Med. 2000; 7:157-161. 

Golden DBK. Stinging insect allergy. Am Fam Physician. 2003;67 :2541-2546. 

Manning SE, Rupprecht CE, Fishbein D, et al. Human rabies prevention-United States 2008: recommendation of the Advisory Committee on Immunization Practices; CDC. MMWR Recomm Rep. 2008:57:1-28. 

Schneir AB. Bites and stings. In: Tintinalli JE, StapczynskiJ, Ma 0, et al. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. New York, NY : McGraw-Hill Education; 2011. Available at: http://accessmedicine.mhmedical.com. Accessed May 25, 2015. 

Schwab RA, Powers RD. Puncture wounds and bites. In: Tintinalli JE, Stapczynski J, Ma 0, et al. eds. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. New York, NY: McGrawHill Education; 2011. Available at: http://accessmedicine.mhmedical.com. Accessed May 25, 2015. 

Suchard JR. "Spider bite" lesions are usually diagnosed as skin and soft-tissue infections. J Emerg Med. 2011; 41(5):473-481. 

Turner TW. Do mammalian bites require antibiotic prophylaxis? Ann Emerg Med. 2004; 44:274-276.

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