Hymenoptera Stings (Bee, Vespids and Ants)


Article Author:
Faizan Arif


Article Editor:
Mollie Williams


Editors In Chief:
Timothy Craig
Yoon Kim
Robert Hostoffer


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
4/20/2019 10:53:00 PM

Introduction

The Hymenoptera order includes over 150,000 different species of flying and non-flying insects. Some species within this order have modified ovipositors (female reproductive organ) which can also act as stingers. Hymenopteran stings only cause local inflammation in most people. However, they also account for the largest percentage of envenomation-related deaths in the United States. Most deaths result from immediate hypersensitivity reactions and anaphylaxis. This review article concentrates on the most common and clinically relevant species: Apidae (bees), Vespidae (wasps, yellow jackets, hornets), and Formicidae (specifically, fire ants). All 3 of these species inject venom, via modified ovipositors in their abdomen (stingers), into prey or as a defense mechanism.

Etiology

The Apidae family (honey bees, bumble bees, among others) are usually not aggressive and only sting when threatened or provoked. However, there is a subset of “Killer Bees” or “Africanized bees,” that are very defensive, often aggressive, and tend to swarm. These Killer Bees were introduced in Brazil in the 1950s, but have since spread to other areas in South and North America (Southwestern United States). They are an invasive species and account for many deaths associated with bee stings. The Apidae family use barbed stingers, which often remain attached in the skin after a single sting.

The Vespidae family (wasps, yellow jackets, hornets) are known to be more aggressive than their Apidae relatives. They are found in all 50 states. They can be classified as solitary or social wasps. Social wasps, including the yellow-jacket and hornet, commonly make larger nests in the ground (yellow jacket) or shrubbery/trees (hornet). Solitary wasps (mud wasp) usually make smaller nests in areas such as the sides of windows. Unlike the Apidae, Vespidae family does not have a barbed stinger and hence, can sting multiple times. 

The Formicidae family includes all ants. Most ants bite with pincer-shaped mandibles; however, similar to the Apidae and Vespidae, some ants have developed the ability to sting with stingers in their abdomens. Fire ants (Solenopsis), are an aggressive species that use their pincer mandibles to latch on to their target and then use their stinger to administer multiple doses of venom. These ant colonies are most commonly found in the southeastern United States but are spreading fast and becoming more common in bordering areas. Other species in the Formicidae family also use stingers but are not found in the United States, so these are not included in this discussion.

Epidemiology

Hymenoptera stings can happen in any age group, and the insects are not selective to a particular gender. Humans are most often stung by either accidental contact with a solitary worker (single sting from a single insect) or because they are near a disrupted nest (multiple stings from multiple insects). Occupations that may increase the risk of exposure to these stings include, but are not limited to, construction workers, landscapers, entomologists, beekeepers, exterminators, among others. Vespidae (specifically hornets and yellow jackets) are likely the culprits in most situations due to their aggressive and territorial nature. Most sting reactions are self-limited, result in a small area of local inflammation, and resolve within a few days. Other local reactions, may be larger, more painful and last longer. These are less common (less than 10%) and termed large local reactions (LLRs) and may require medical intervention. Systemic reactions, are far less common but can be fatal if they occur.

Pathophysiology

Hymenoptera stings cause reactions by injecting venom via their ovipositors into their target. The venom for Apidae, Vespidae, and Formicidae have some similar characteristics, consisting of a mixture of smaller, low-molecular-weight, proteolytic enzymes (hyaluronidase, proteases, phospholipase, acid phosphatase), lipids, carbohydrates, and also high-molecular-weight proteins which act as allergens. The low-molecular-weight components are responsible for local inflammatory reactions while the high-molecular-weight component is integral to the systemic reaction (in other words, anaphylaxis). When the venom is introduced into the skin, the proteolytic enzymes begin to degrade the surrounding tissue. The release of histamine from mast cells and basophil activation, in response to the venom, causes vasodilation and the ensuing inflammatory response: edema, pain, erythema, and increased warmth. Fire ant venom is primarily made of alkaloids that result in the characteristic sterile pustules associated with these stings. Large, local reactions (LLRs) develop in about 10% of Hymenoptera stings and are believed to be immune IgE-mediated. Anaphylaxis develops in people with preformed antibodies to the high-molecular-weight aspects of these venoms. These reactions, like other anaphylactic reactions to allergens, occur via a systemic IgE-mediated histamine release. The resulting mast cells and basophil activation can cause systemic vasodilation, angioedema, urticaria, hypotension/shock, and death.

History and Physical

Hymenoptera stings are almost always diagnosed clinically. For this reason, it is very important to get a good history. Patients with uncomplicated, local reactions typically present complaining of pain and swelling after a presumed or witnessed sting. Apidae and Vespidae stings usually cause immediate pain. The venom then causes a local reaction within minutes that can last for hours. Symptoms include pain, swelling, pruritis, bleeding. On exam, you may find erythema, edema, induration, increased warmth. In some instances, one may also see a stinger still attached in the skin (Apidae). Stingers are usually still attached to the venom sac and so should be removed from the skin by scraping, for example, with a credit card, not by squeezing or with tweezers). Fire ant stings also cause pain immediately with an associated burning/itching sensation which lasts a few minutes, then a wheal with surrounding erythema forms. Patients can also develop a sterile pustule within 24 hours. Most Hymenoptera sting reactions are self-limited, result in a small area of local inflammation, and resolve within a few days. LLRs may be larger (greater than 10 cm), more painful, and persist for a longer duration. The exaggerated response to the venom is likely secondary to an IgE mediated mechanism. These reactions typically worsen over 48 hours and then resolve within 7 to 10 days.[1][2][3][4]

Systemic reactions often present as severe anaphylaxis, are rapid in onset, and life-threatening. Patients may have a history of anaphylaxis or a similar systemic reaction in the past secondary to insect stings. Patients present in extremis with rapidly worsening symptoms, including generalized urticaria, angioedema, flushing, difficulty breathing, wheezing, hypotension/shock.

Evaluation

ABCs

Evaluate Airway, Breathing, Circulation first.

Uncomplicated Local Reactions

Include a small area of focal edema, induration, increased warmth, and tenderness

Large Local Reactions (LLRs)

Greater than a 10-cm area of erythema, induration, increased warmth, larger, and last longer than uncomplicated local reactions

Systemic Reactions (Anaphylaxis)

Includes generalized urticaria, angioedema/facial swelling, stridor, respiratory distress/wheezing secondary to bronchospasm, abdominal pain, nausea, vomiting, flushing

Treatment / Management

Uncomplicated, local reactions can be treated with supportive care (ice packs, NSAIDs/APAP for pain, H1/H2 blocker). Within the first few minutes after the sting, the stinger should be removed via scraping with a credit card rather than squeezing/tweezing to avoid further venom exposure.

Large local reactions should also be treated with supportive care along with glucocorticoids (usually a burst course of prednisone 40 to 60 mg per day for 3 to 5 days) to decrease the inflammatory response and improve symptoms.

Systemic reactions (anaphylaxis) are life-threatening and should be managed as such. ABCs first. The airway can be lost within seconds to minutes, so intubate early. As with any anaphylactic reaction, epinephrine, corticosteroids, H1 and H2 antagonists, and intravenous (IV) fluids should be given immediately. Epinephrine 0.3 to 0.5 mg should be given intramuscularly (IM) to the anterolateral thigh. This may be repeated every 5 to 15 minutes. The alpha1-mediated increase in vascular tone, beta1-mediated increase in inotropic/chronotropic cardiac activity, and B2-mediated bronchodilation all help to reverse anaphylaxis. Corticosteroids (prednisone, methylprednisolone, dexamethasone) act to decrease inflammation and immune response to the antigen. H1 and H2 antagonists block the effects of histamine decreasing pruritis, erythema, and urticaria.

Differential Diagnosis

  • Anaphylaxis to any allergen
  • Other insect bites
  • Cellulitis
  • Abscess
  • Folliculitis

Prognosis

The prognosis for most Hymenoptera stings is very good. Most patients have anywhere from a few minutes to a couple of days of discomfort. For patients with severe systemic reactions, mortality is often high, unless treated promptly. All patients with a history of severe reactions to insect bites should avoid Hymenoptera insects to the best of their ability and carry an epinephrine auto-injecting pen at all times.

Pearls and Other Issues

  • Inject epinephrine to anterolateral thigh above the deltoid.
  • Epinephrine may not work for patients on beta-blockers. In this case, give glucagon to bypass the adrenergic receptors and directly activate cAMP intracellularly.
  • Stay away from nests or hives and people disturbing nests or hives.
  • Fire ant stings characteristically cause sterile pustules in 24 hours. Do not unroof these pustules to avoid secondary infections.
  • Serum-sickness reactions may occur up to 14 days after a sting and may include life-threatening conditions such as myocardial infarction, renal failure, DIC, and cerebral edema.

Enhancing Healthcare Team Outcomes

Ant/bee stings are very commonly encountered in the emergency department. While minor stings can be managed with supportive care, serious stings associated with anaphylaxis are best managed by a multidisciplinary team that includes the emergency department physician, specialty nurse, anesthesiologist, poison control and an intensivist.

Systemic reactions (anaphylaxis) are life-threatening and should be managed with the ATLS protocol.  Epinephrine and corticosteroids can be life-saving. [5][6]

All patients with allergies should be told to carry epinephrine on them. Parents should avoid taking their children to areas where ants/bees are common. 

 


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Hymenoptera Stings (Bee, Vespids and Ants) - Questions

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What is the drug of choice for a patient with allergies to bees and multiple bee stings?



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What primarily mediates the skin swelling that occurs after a bee sting?



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A patient who has a well-documented history of allergies is stung by a bee. The affected area swells within 5 minutes. Which of the following mediators most likely accounts for this reaction?



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A patient returns to the emergency department after being seen 16 hours earlier for a bee sting. He was given several injections of epinephrine. He improved and was discharged. Now he is anxious and hoarse, but his lungs are clear. An insect stinger surrounded by urticaria is noted. Which of the following is not appropriate in the initial management of this patient?



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Which of the following is not true about bee sting reactions?



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Which of the following is the most appropriate therapy for a patient having a local reaction to a hymenoptera sting?



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A patient is stung by a wasp and there is rapid development of swelling and redness locally. Select the mediator that most likely caused this response.



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A patient is stung by a bee and develops redness and swelling. Which of the following is the cause of the swelling?



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The American Red Cross recommends the removal of a bee stinger with which of the following?



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What proceeds most fatal Hymenoptera (wasp, bee, ant) stings?



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A patient develops inflammation at the site of a wasp sting. He previously suffered an urticarial reaction at the time and was treated with antihistamines and adrenalin. The site is erythematous and edematous. On further investigation what do you suspect you will find?



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Hymenoptera Stings (Bee, Vespids and Ants) - References

References

Brzyski P,Cichocka-Jarosz E,Tarczoń I,Jedynak-Wąsowicz U,Tomasik T,Lis G, Health-related quality of life in children and adolescents after systemic sting reaction. Annals of agricultural and environmental medicine : AAEM. 2019 Mar 22;     [PubMed]
Soyyigit S,Arslan S,Caliskaner AZ, Investigation of the factors that determine the severity of allergic reactions to Hymenoptera venoms. Allergy and asthma proceedings. 2019 Mar 1;     [PubMed]
Warrell DA, Venomous Bites, Stings, and Poisoning: An Update. Infectious disease clinics of North America. 2019 Mar;     [PubMed]
Wu DJ,Lee J,Chavez A,Kawaoka JC, Wilderness Dermatology: Bugs, Plants, and Other Nuisances That May Ruin Your Hike. Rhode Island medical journal (2013). 2019 Feb 1;     [PubMed]
Song TT,Lieberman P, Who needs to carry an epinephrine autoinjector? Cleveland Clinic journal of medicine. 2019 Jan;     [PubMed]
Carneiro-Leão L,Amaral L,Coimbra A, Reasons for Declining Venom Immunotherapy. Acta medica portuguesa. 2018 Nov 30;     [PubMed]

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