Hymenoptera Stings Clinical Presentation

Updated: Aug 30, 2017
  • Author: Randy Park, MD; Chief Editor: Joe Alcock, MD, MS  more...
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Presentation

History

A patient's reaction to a Hymenoptera sting determines the treatment required. Reactions may be graded as local, urticaria without systemic symptoms, and generalized. Emergency physicians should attempt to determine degree of reaction based on both patient history and a physical examination.

Rapid onset of symptoms is the rule; 50% of deaths occur within 30 minutes of the sting, and 75% occur within 4 hours.

Fatal allergic reactions can occur as the first generalized reaction. Far more common, however, is a fatal reaction following a previous, milder generalized reaction. The shorter the interval since the last sting, the more likely it is that a severe reaction will take place.

Large local reactions do not predispose patients to generalized reactions. Local reactions may be life threatening if local swelling at the sting site compromises the airway. Local reactions to stings can cause peripheral nerve block.

Local reactions may produce the following:

  • Pain occurs immediately after sting.
  • Edema is marked and may extend to 10 cm from site of envenomation.
  • The insect frequently is seen by patient and may be identified from the description.
  • Bleeding may occur at site of sting.
  • Pruritus is common.
  • Vasodilation may produce a sensation of warmth.
  • The stinging apparatus may have been seen in the wound and removed prior to presentation.
  • Nausea or vomiting may occur without generalization.
  • If Hymenoptera are swallowed, stings can cause painful swelling in the mouth or esophagus.
  • Visceral pain may occur with stings in the gastrointestinal (GI) tract after ingestion of the insect.

Urticaria may occur with or without the symptoms noted in local reaction.

Generalized reactions may produce the following symptoms:

  • Urticaria
  • Confluent red rash
  • Shortness of breath, wheezing
  • Edema in airway, tongue, or uvula
  • Weakness, syncope
  • Anxiety, confusion
  • Chest pain
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Physical Examination

Local reactions may include the following:

  • Erythema, edema, warmth, tenderness
  • Drainage from site of sting
  • Compromised distal circulation as result of edema
  • Distal sensation loss from stings over peripheral nerve
  • Corneal ulceration from corneal stings
  • With bee stings, stinging apparatus visible at sting site
  • If Hymenoptera are swallowed, painful swelling in the mouth or esophagus
  • Ant stings: Vesicles from fire ants, classic arc of fire ant stings, and ant stings on mucous membranes or conjunctival surfaces cause dramatic swelling in patients who are sensitive. See the image below.
  • Fire ant bites. In less than 10 seconds, an unwary Fire ant bites. In less than 10 seconds, an unwary scientist was stung over 250 times on one leg when he carelessly knelt on a collapsed fire ant mound. The sterile pustules developed to this stage in 3 days. US Department of Agriculture. Courtesy of Wikimedia Commons.

Urticaria or generalized redness may develop without systemic symptoms.

Generalized reactions may include the following symptoms:

  • Urticaria
  • Vomiting
  • Wheezing
  • Tachypnea
  • Hypotension
  • Laryngoedema, lingular edema, uvular edema
  • Delirium, shock
  • Respiratory arrest
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Causes

Hymenoptera are social creatures that typically sting to protect their colony, nest, or hive. Most stings are incited by proximity to the colony. Noisy or vigorous activity (eg, lawn mowers, weed eaters), bright or dark colors, and perfumes also may incite stings. When a colony is disturbed, many Hymenoptera release defense pheromones that attract other members of the colony to sting. These pheromones are released during stinging or when an insect is smashed.

Although bee and wasp venom varies from species to species, all venom is composed primarily of proteins, peptides, and amines. Toxic components include phospholipase, histamine, bradykinin, acetylcholine, dopamine, and serotonin. In addition, mast cell degranulating (MCD) peptide and mastoparan are peptides that can cause degranulation of mast cells and result in an anaphylactoid reaction. Molecule size and the presence of protein enhance the antigen properties of venom, making it a potent activator of the immune system. Most significant reactions are mediated through true IgE allergic mechanisms that activate mast cell degranulation.

Anaphylactoid reactions may occur. However, venom load may be sufficient to cause fatal injury without the added effects of the endogenous system. This may result from as few as 30 vespid stings or 200 honeybee stings. Since the compounds are similar in anaphylactic and toxic reactions, pathology and treatment also are similar.

Bees and wasps sting through a modified ovipositor. They puncture the skin with a hollow stinger and then inject venom. Bees leave their barbed stinger in the skin along with its stinging apparatus, killing the bee. Vespids have smooth or less-barbed stingers and can sting more than once. Vespids are responsible for almost twice as many allergic reactions as honeybees. Retained stingers can cause granuloma formation and subsequent epidermal necrosis.

"Killer" bee is the moniker applied to the Africanized honeybee (Apis mellifera scutellata), which was originally introduced into the New World as a hybrid of European honeybees and a variety of honeybee from Africa. Toxicity from the sting of a single Africanized bee is no worse than the sting of a single European bee. Africanized honeybees show behavioral changes, including increased defensive stinging. One pheromone, isoamylacetate, has been isolated as a mediator of aggressive group-defensive behaviors in Africanized bees. Africanized bees defend their hive up to a 150-yard radius, three times the distance of European bees. As of May 2000, Africanized bees have migrated from their western-hemisphere origin in Brazil to Texas, Arizona, California, New Mexico, Nevada, Utah, Alabama, Louisiana, Arkansas, Oklahoma, and Florida, according to the US Department of Agriculture. [9] Multiple stings from these species are more common. Honeybees fly at only 4 mph, allowing most victims to flee after only a few stings. Overwhelming numbers of stings usually occur in young patients or in those slowed by physical limitations or intoxication.

In addition to reaction to stings, bee venom may be encountered as a result of apiotherapy, a modality used in traditional Chinese medicine. In this treatment, ointment containing bee venom is applied to skin or eye and may result in an immunologic reaction.

Ant stings

Ants account for one half of all insects. While many ant species sting, the most aggressive in the United States are imported fire ants, Solenopsis invicta. These ants fiercely guard their territory and attack intruders in large numbers, inflicting thousands of stings and bites to victims unable to escape. Fire ant venom is 95% alkaloid, which is unique among ants. A fire ant typically bites with its mandibles, then swivels its abdomen and stings repeatedly in an arc about the bite site. Their stings develop into sterile pustules and then rupture, leaving crusted wounds that may become infected secondarily. Patients have survived as many as 5000 fire ant stings. Brazilian fire ants, S invicta, have nearly eradicated native ant species in their range from Florida to Texas and north to Arkansas and South Carolina. S invicta is found in South and North America in areas where mean high temperatures are 15°C or higher.

Stings from other ants often closely resemble those of wasps and bees, although with less tissue destruction and less severity. Harvester ants, Pogonomyrmex species, inject venom containing a hemolysin. This sting frequently creates an ecchymotic area surrounding the sting site. Some species of field ants truly bite with the mandible and spray the acidic toxin into the wound without injecting venom. Formic acid, a component of ant venom uncommon in bee or wasp stings, is derived from the superfamily name Formicidae. Ant stings cause generalized reactions less often than stings from flying Hymenoptera.

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Complications

Sting sites may become infected. Infection is more common in fire ant stings because they frequently are multiple; stings vesiculate and then ulcerate, leaving pruritic open wounds.

Rebound anaphylaxis may occur in patients with generalized reactions as antihistamine and alpha-agonist levels subside after treatment.

Anaphylaxis may occur in susceptible patients from exposure to other insect-related material, including honey and apiotherapy.

Serum-sickness-type reactions may occur up to 14 days after a sting.

Myocardial infarction, [10] renal failure, DIC, rhabdomyolysis, [11] and cerebral edema may occur after a bee sting. [12] One case report documents transient inferior ST-segment elevation consistent with myocardial ischemia after a single wasp sting in a 58-year-old man. [13]  In a retrospective analysis of medical records from 1985-2007, 7 of 45 pediatric patients were noted to have developed acute renal failure after a wasp sting. [14]

Peripheral nerve block may occur if sting is near the path of a nerve.

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