Hymenoptera stings


Hymenoptera stings account for more deaths in the United States than any other envenomation.

The order Hymenoptera includes Apis species, ie, bees (European, African), vespids (wasps, yellow jackets, hornets), and ants.

Insect stings cause systemic reactions in about 3% of US adults.

More than 20% of adults are sensitized to insect venom but are not substantially elevated risk for anaphylaxis.

About 10% of the general population experience large local reactions from insect stings and can be treated symptomatically with a short course oral corticosteroids for severe swelling and since risk for anaphylaxis is less than 5%, venom immunotherapy is not indicated.

At least 40 patients die annually in the US from these things, and they account with 20% of all anaphylaxis related deaths.

In patients with severe systemic reactions, 50% will experience anaphylaxis to future stings.

With venom immunotherapy the risk of anaphylaxis in high-risk patients is less than 5%.

Apidae-honeybees, bumblebees.

Vespidae-hornets, wasps, yellow jackets.

Formicidae-fire ants.

Most deaths result from immunologic mechanisms.

Some deaths may result from direct toxicity.

Severe anaphylactoid reactions occur when toxins directly stimulate mast cells.

Vast majority of stings cause only minor problems.

The sting apparatus of Hymenoptera is a modified ovipositor, therefore only female insects can sting.

Venom from stings is primarily used to defend the hymenoptera and their nests.

Hymenoptera deliver between 50 ng for fire ants, and up to 50 µg for bees of venom with each sting.

Stings do, however, cause a significant number of deaths.

Target organs are the skin, vascular system, and respiratory system.

Pathophysiology is related to immunoglobulin E (IgE)–mediated allergic reactions.

Venoms of hymenoptera contain vasoactive amines, including histamine, dopamine, norepinephrine and kinins which account for painful erythematous swellings and itching at the site of the sting.

The major allergens in the venom that lead to systemic reactions in allergic individuals are primarily protein enzymes such as phospholipase, hyaluronidase, and acid phosphatase.

Fire ant venom contains a small amount of proteins, but significant amounts of toxic alkaloids causing characteristic vesicles.

If swallowed stings can cause painful swelling in the mouth or esophagus.

Venoms are composed primarily of proteins, peptides, and amines, and additional toxic components include phospholipase, histamine, bradykinin, acetylcholine, dopamine, serotonin, and peptides mast cell degranulating (MCD) peptide and mastoparan.

All patients with severe systemic reaction should be ref2241ed for allergy testing and should receive venom immunotherapy for five years.

Patients with severe systemic reactions should carry self injectable epinephrine and medical identification.

Peptides can cause degranulation of mast cells and result in an anaphylactoid reaction.

Proteins enhance the antigen properties of venom, activating the immune system, with significant reactions are mediated through true IgE allergic mechanisms that result in mast cell degranulation.

While anaphylactoid reactions may occur, a large venom load may be sufficient to cause fatality from a toxic injury without eliciting such a response.

Beta blockers and angiotensin converting enzymes may heightened risk for serious adverse events from stings or venom immunotherapy.

Bees and wasps sting through a modified ovipositor, puncturing the skin with a hollow stinger and then injecting 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, and their retained stingers can cause granuloma formation and subsequent epidermal necrosis.

Vespids are responsible for almost twice as many allergic reactions as honey bees.

Africanized honeybee or killer bees (Apis mellifera scutellata), the offspring of aggressive wild African honeybees and domesticated European honeybees display aggressive defensive behavior.

The pheromone, isoamylacetate, is the mediator of this activity, and the Africanized bees defend their hive up to 3 times the distance of European bees.

Hymenoptera fly at only 4 mph, allowing most victims to flee, however, young patients or in those slowed by physical limitations or intoxication, can be stung innumerable times.

Ants account for one half of all insects and there many ant species sting: the most aggressive in the United States are imported fire ants, Solenopsis invicta.

These ants can inflict thousands of stings and bites to victims unable to escape.

Fire ant venom is 95% alkaloid, which is unique among ants.

A fire ant bites with its mandibles, and stings repeatedly, with the development of sterile pustules that rupture, and leave crusted wounds that may become infected.

Stings from other ants resemble those of wasps and bees, with less tissue destruction.

Harvester ants, Pogonomyrmex species, inject venom containing a hemolysin, resulting in ecchymoses.

Ant stings cause generalized reactions less often than stings from flying Hymenoptera.

The stinger should removed as quickly as possible with bee stings since the stinging apparatus actively injects venom into the wound for 1 minute after the sting.

Prehospital care must assess severity of the reaction and provide immediate therapy, as the most endangered patients die within 30 minutes of a sting.

Local reactions can be life threatening if swelling occludes the airway, and life saving invasive measures to secure the airway may be required.

Diphenhydramine limits the size of the local reaction.

The wound should be cleaned and the stinger if present removed.

The stinger should be removed as soon as possible, as delay increases venom load.

Generalized reactions are treated as for anaphylaxis with fluid resuscitation, diphenhydramine and epinephrine.

Administration of intramuscular or subcutaneous epinephrine should be initiated immediately in the event of severe reaction.

Corticosteroids should be administered in severe cases to prevent recurrent or prolonged anaphylaxis, although they are not likely to improve acute symptoms.

H2 blockers may be given intravenously, combined with diphenhydramine.

Vasopressors can be used to provide vascular support.

Patients may require ventilatory support.

Repeated doses of epinephrine may be required for severe cases.

In the event of cardiopulmonary arrest due to anaphylaxis, intravenous epinephrine should be administered.

All patients with generalized reactions must have allergy care because risk of fatal reaction is inversely related to length of time since the last sting.

Antihistamines directly block effects of some venom and effects of endogenously released histamine.

Rebound phenomena may occur up to 12 hours after sting

Patients with generalized reactions should have allergy testing and desensitization.

Patients with generalized reactions should have means to self-administer epinephrine and diphenhydramine, and should be advised to wear medic alert bracelets.

Treatments with steroids should continue for 3-5 days, and antihistamines for at least 24 hours.

Sting sites should be cooled for 12 hours, and extremities with stings elevated for 12 hours to decrease edema.

Avoiding stings in hypersensitive persons is essential, and behavior includes: avoiding using perfumes outdoors, that may attract flying Hymenoptera, avoid wearing bright colors, avoid hives, nests, and avoiding loud equipment near hives,

Killing bees or wasps incites others to sting.

Patients are considered for potential immunotherapy and desensitization.

Venom-specific immunotherapy offers long-term protection in 85-95% of cases.

Sting sites may potentially become infected.

Fire ant stings are commonly secondarily infected as they are frequently multiple, undergo vesiculation and then ulceration, leaving pruritic open wounds.

Following treatment for generalized reactions, rebound anaphylaxis may occur when antihistamine and alpha-agonists levels dissipate.

Serum-sickness, myocardial infarction, cerebral edema, acute renal failure, and DIC may occur following a sting.

Most stings resolve with no residual problems and major local reactions do not predispose patients to generalized reactions in the future.

Less than severe generalized reactions precede most fatal reactions.

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