Fire Ant Bites


Article Author:
Brian Kruse
Jackie Anderson


Article Editor:
Leslie Simon


Editors In Chief:
David Tauber


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Frank Smeeks
Kristina Soman-Faulkner
Trevor Nezwek
Radia Jamil
Patrick Le
Sobhan Daneshfar
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Pritesh Sheth
Hassam Zulfiqar
Navid Mahabadi
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Mark Pellegrini
James Hughes
Beata Beatty
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
6/28/2019 9:05:55 PM

Introduction

Fire ants tend to be an aggressive insect that will sting causing very painful reactions.  There are two types of fire ants which belong to the Solenopsis species. The first is a red, imported fire ant, Solenopsis invicta and the second is the black imported fire ant, Solenopsis richteri. They were introduced into the United States at Mobile, Alabama about 40 years ago. Red fire ants are predominately seen in 14 states: Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, New Mexico, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia. Worldwide locations include the Caribbean islands, Puerto Rico, the Bahamas, the British and United States Virgin Islands, Antigua, and Trinidad, Australia, New Zealand, Taiwan, and China.

The black fire ant is seen only in northern Alabama, northern Mississippi, and southern Tennessee.

Over the next decade, the fire and Solenopsis invicta is expected to spread to California and towards the Pacific coast nearing the Canadian border.

Fire ants do not need to be provoked to attack, and their venom is capable of causing a painful local reaction and, in some instances, result in life-threatening anaphylaxis. [1][2][3]

Etiology

Ant bites usually occur when their nest is disturbed. They will swarm and sting any living human or animal with which they come in contact.  One ant is capable of multiple stings within a very short time frame. Bites can occur year-round but are most common in the summer months.  [4][5][6]

Epidemiology

Ant bites occur most commonly in children, usually on the lower extremities. Patients who are less mobile are also at risk because they are less aware of their environment and often are not able to move away from the ants. Ants do not discriminate between age or sex and will attack any living animal.[7]

Pathophysiology

When the ant stings, it does so with its mandible, which locks onto its prey. It arches its body and then injects venom through the stinger located on the abdomen. As it stings, it does so at an average of 7-8 stings. It rotates its body which results in a circular pattern resulting in pain and itching at the site. The venom of the fire ants is used to immobilize or kill prey for food yet has also demonstrated insecticidal, bactericidal, and fungicidal activity. The venom is 95% water-insoluble alkaloid, with the remaining 5% being an aqueous protein solution. It is the alkaloid part of the venom that causes a sterile pustule at the sting site and has cytotoxic and hemolytic properties. The protein portion contains the allergens. The reactions range from immediate localized wheal and flare responses to large, local or systemic reactions which can include anaphylaxis. 

The immediate reaction to the venom is an intense burning sensation which explains the common name of the ants. When the sensation subsides after a few minutes, a dermal flare and wheal occur and papules form within two hours. Vesicles develop within four hours and by 24 hours these develop into sterile pustules. A pustule forms as a result of the venom alkaloids, but it is not allergenic.

Another response is the large local reaction, which is characterized by a reaction larger than 10 cm in diameter and associated with localized erythema and edema. They are very painful and pruritic, lasting 24 to 72 hours. 

The local reactions of the fire ant sting can cause anaphylaxis, which is a response to the aqueous protein solution. Anaphylaxis usually occurs in those sensitized by a previous sting. These symptoms include flushing, generalized urticaria, angioedema, laryngeal edema, bronchospasm, or loss of consciousness.

Fire ant stings also are capable of causing serum sickness, nephrotic syndrome, seizures, worsening of pre-existing cardiopulmonary disease, and anaphylaxis.

Histopathology

The local reactions are IgE-mediated, with the resulting lesion comprised of a dense fibrin gel along with eosinophils, neutrophils, and lymphocytes. Cutaneous systemic allergic reactions include urticaria, angioedema, pruritus, and erythema as well as severe, life-threatening bronchospasm or laryngeal edema. One sting can cause anaphylaxis. The identifying hallmark of fire ant envenomation is the pustules that form after the sting.

History and Physical

The most common scenario is one where the patient is outside, in the yard or the woods, and is standing on or near an ant nest. Disrupting the nest causes a large number of ants to swarm and attack. However, the imported fire ant can attack with little warning. The ants will swarm and repeatedly sting the lower body. The most common reaction is a wheal and flare, which is a lesion that has resembles a hive but also is surrounded by erythema. The stings are very painful and cause intense itching. A second lesion that can result is a sterile pustule that develops within the first 24 hours and is filled with yellow fluid. They are sterile and are the result of the venom alkaloids lasting for about one week. A large, local reaction, typically over 10cm in diameter, may occur which has a pustule on top of a painful inflamed and swollen area. Lastly, anaphylaxis is possible. However, these reactions typically occur in those who have been stung by an ant or a yellow jacket once before as its venom is known to cross-react with the Solenopsis venom in vitro.

Evaluation

Diagnosis of ant-induced hypersensitivity can be performed by a patient history of allergic reaction to stings, by physical examination, or through the use of in vivo or in-vitro tests. Useful clinical clues to aid in the diagnosis of a fire ant bite include the development of a typical pustule at the sting site after 24 hours. Identification of the ant is helpful in the diagnosis. The most specific diagnosis comes from the clinical manifestations of fire ant sting reactions with IgE detection by skin testing.

Treatment / Management

Most ant bites require supportive care, so treatment is aimed at preventing secondary bacterial infections if a pustule is disrupted. The use of topical hydrocortisone or antihistamine cream is usually all that is needed. The sterile pustules should be left alone, however, if they are broken then they need to be cleaned with soap and water and an antibiotic cream placed on top. If the broken lesion gets infected, then a proper antimicrobial can be used. Those with large local reactions will benefit from a single dose of 20 mg prednisone. Localized pain and swelling may be improved with cold compresses. Anaphylactic reactions are treated the same as any other anaphylaxis, using epinephrine first followed by steroids, antihistamine, and H2 blocker. Fluid resuscitation and oxygen therapy should be included as part of supportive treatments.[8][9]

Differential Diagnosis

One must be aware of other potential insects that sting, such as a yellow jacket or bee. Most local reactions have erythema, so differentiating this from cellulitis is important. Patients who have had hypotension with stings should be evaluated for mast cell disorders and have a baseline tryptase level ordered.

Prognosis

The prognosis is very good for patients presenting with ant bites as most bites are managed conservatively not requiring extensive care. Patients who seek medical care demonstrate serious systemic allergic reactions which occur in about 2% of fire ant stings. One study reported 83 deaths out of 29,300 patients. Infants and the elderly were the most at risk.

Pearls and Other Issues

First Aid

Rub off ants briskly, as they are able to attach to your skin and sting multiple times. Antihistamines and corticosteroid creams may help. If you develop severe chest pain, nausea, sweating, shortness of breath, severe swelling or slurred speech, seek immediate medical attention.  

Avoidance 

Do not disturb ant mounds. Be cautious when lifting any items off the ground as ants may be underneath. Tuck pants into socks or boots. A person with a known, severe allergy to insect bites or stings should carry an epinephrine auto-injector and wear medical identification jewelry listing the allergy.

Enhancing Healthcare Team Outcomes

Fire ant bites are not uncommon in souther USA. Since most patients present to the emergency room following a fire ant bite, the triage nurse must know the signs and symptoms of the disorder. Because the fire ant bite can be associated with a serious allergic response, timely admission and treatment is mandatory. for the most part, the bite of a fire ant is managed with supportive care, but sometimes one may need to an antihistamine and an NSAID to decrease the itching and pain. Personnel in the emergency room must be familiar with the use of epinephrine in case a patient has an anaphylactic shock.  A person with a known, severe allergy to insect bites or stings should carry an epinephrine auto-injector and wear medical identification jewelry listing the allergy.


  • Image 5884 Not availableImage 5884 Not available
    Contributes by the Public Domain
Attributed To: Contributes by the Public Domain

Interested in Participating?

We are looking for contributors to author, edit, and peer review our vast library of review articles and multiple choice questions. In as little as 2-3 hours you can make a significant contribution to your specialty. In return for a small amount of your time, you will receive free access to all content and you will be published as an author or editor in eBooks, apps, online CME/CE activities, and an online Learning Management System for students, teachers, and program directors that allows access to review materials in over 500 specialties.

Improve Content - Become an Author or Editor

This is an academic project designed to provide inexpensive peer-reviewed Apps, eBooks, and very soon an online CME/CE system to help students identify weaknesses and improve knowledge. We would like you to consider being an author or editor. Please click here to learn more. Thank you for you for your interest, the StatPearls Publishing Editorial Team.

Fire Ant Bites - Questions

Take a quiz of the questions on this article.

Take Quiz
From where does the ant sting originate?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which portion of the fire ant venom causes the allergic reaction?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which species of fire ant is native the United States?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up

Fire Ant Bites - References

References

Villada G,Hafeez F,Ollague J,Nousari CH,Elgart GW, Imported fire ant envenomation: A clinicopathologic study of a recognizable form of arthropod assault reaction. Journal of cutaneous pathology. 2017 Dec;     [PubMed]
Potiwat R,Sitcharungsi R, Ant allergens and hypersensitivity reactions in response to ant stings. Asian Pacific journal of allergy and immunology. 2015 Dec;     [PubMed]
Srisong H,Daduang S,Lopata AL, Current advances in ant venom proteins causing hypersensitivity reactions in the Asia-Pacific region. Molecular immunology. 2016 Jan;     [PubMed]
Tankersley MS,Ledford DK, Stinging insect allergy: state of the art 2015. The journal of allergy and clinical immunology. In practice. 2015 May-Jun;     [PubMed]
Hemmer W, [Cross reactions between Hymenoptera venoms from different families, genera and species]. Der Hautarzt; Zeitschrift fur Dermatologie, Venerologie, und verwandte Gebiete. 2014 Sep;     [PubMed]
Arseneau AM,Nesselroad TD,Dietrich JJ,Moore LM,Nguyen S,Hagan LL,Tankersley MS, A 1-day imported fire ant rush immunotherapy schedule with and without premedication. Annals of allergy, asthma     [PubMed]
Vinson SB, Impact of the invasion of the imported fire ant. Insect science. 2013 Aug;     [PubMed]
Koterba AP,Greenberger PA, Chapter 4: Stinging insect allergy and venom immunotherapy. Allergy and asthma proceedings. 2012 May-Jun;     [PubMed]
Ownby DR,Partridge ME,Wegienka GR,Woodcroft KJ,Peterson EL,Joseph CL,Williams LK,Johnson CC, Influence of dose and frequency of antigen injection on IgE development in young children: a comparison of fire ant stings and tetanus immunizations. Annals of allergy, asthma     [PubMed]

Disclaimer

The intent of StatPearls is to provide practice questions and explanations to assist you in identifying and resolving knowledge deficits. These questions and explanations are not intended to be a source of the knowledge base of all of medicine, nor is it intended to be a board or certification review of EMS-Wilderness Medicine. The authors or editors do not warrant the information is complete or accurate. The reader is encouraged to verify each answer and explanation in several references. All drug indications and dosages should be verified before administration.

StatPearls offers the most comprehensive database of free multiple-choice questions with explanations and short review chapters ever developed. This system helps physicians, medical students, dentists, nurses, pharmacists, and allied health professionals identify education deficits and learn new concepts. StatPearls is not a board or certification review system for EMS-Wilderness Medicine, it is a learning system that you can use to help improve your knowledge base of medicine for life-long learning. StatPearls will help you identify your weaknesses so that when you are ready to study for a board or certification exam in EMS-Wilderness Medicine, you will already be prepared.

Our content is updated continuously through a multi-step peer review process that will help you be prepared and review for a thorough knowledge of EMS-Wilderness Medicine. When it is time for the EMS-Wilderness Medicine board and certification exam, you will already be ready. Besides online study quizzes, we also publish our peer-reviewed content in eBooks and mobile Apps. We also offer inexpensive CME/CE, so our content can be used to attain education credits while you study EMS-Wilderness Medicine.