Adverse reactions to ants other than imported fire ants John H. Klotz, PhD*; Richard D. deShazo, MD†; Jacob L. Pinnas, MD‡; Austin M. Frishman, PhD§; Justin O. Schmidt, PhD¶; Daniel R. Suiter, PhDʈ; Gary W. Price, MD**; and Stephen A. Klotz, MD‡ Objective: To identify ants other than Solenopsis invicta and Solenopsis richteri reported to cause adverse reactions in humans. Data Sources: We conducted a literature review to identify reports of medical reactions to ants other than S invicta and S richteri. Our review of medical and entomological literature on stinging ants was generated from MEDLINE and FORMIS, respectively, using the key words stinging ants and ant stings. The search was limited to articles in English published from 1966 to 2004 on MEDLINE and all years on FORMIS. We also present 3 new case reports of severe reactions to stings by 2 different species of ants, Pseudomyrmex ejectus and Hypoponera punctatissima. Study Selection: Articles that concerned anaphylactic (IgE-mediated) or anaphylactic-like (resembling anaphylaxis but mechanism unknown) immediate reactions to ant stings or bites were included in this review. Results: Taken together, our data demonstrate that S invicta and S richteri are not alone in their capability to cause serious allergic or adverse reactions. A diverse array of ant species belonging to 6 different subfamilies (Formicinae, Myrmeciinae, Ponerinae, Ectatomminae, Myrmicinae, and Pseudomyrmecinae) and 10 genera (Solenopsis, Formica, Myrmecia, Tetramorium, Pogonomyrmex, Pachycondyla, Odontomachus, Rhytidoponera, Pseudomyrmex, and Hypoponera) have now been shown to have this capability. Conclusion: Awareness that species other than imported fire ants may cause severe reactions should lead to more rapid evaluation and treatment and further investigation of the medical entomology of these ants. Ann Allergy Asthma Immunol. 2005;95:418–425. INTRODUCTION Although most allergic reactions to ants occur following The fire ants Solenopsis invicta, Solenopsis richteri, and the imported fire ant stings as previously described, there are also hybrid S invicta x richteri are notorious for their pugnacious risks associated with stings from other species of ants. In behavior and sting both in their native South America and as addition to Solenopsis, other ant genera, including Formica, imported fire ants in the United States. Fire ant venom contains Myrmecia, Tetramorium, Pogonomyrmex, Pachycondyla, piperidines, which cause a burning sensation in stung individu- Odontomachus, Rhytidoponera, Pseudomyrmex, and Hy- als, and proteins, which can cause anaphylaxis in a small per- poponera, have episodically been reported to cause severe centage (Ͻ1%) of those stung.1 Despite the low incidence of reactions. Therefore, we performed a comprehensive review allergic reactions, imported fire ants are a growing public health to identify ants other than S richteri and S invicta reported to risk in the southern United States, with up to 50% of inhabitants cause adverse reactions in humans. In addition, we add to this in fire ant endemic regions being stung per year.1 Caplan et al2 list 3 new case histories of severe reactions to stings by found that 17% of 200 randomly selected Georgians had specific species of ants that have not been previously reported. IgE to the venom of S invicta. With an estimated 77,000,000 people living in areas of the United States infested with fire ants METHODS in the near future, an increasing number of individuals will be at 2 Our review of medical and entomological literature on sting- risk of allergic reaction. Reports of fire ant attacks on debilitated 4 3 ing ants was generated from MEDLINE and FORMIS, re- individuals indoors are increasing. spectively. FORMIS is a master bibliography of ant literature covering the years 1650 to 2000. We used a keyword search on MEDLINE and FORMIS using stinging ants and ant * Department of Entomology, University of California, Riverside. stings. The search was limited to articles in English from † Department of Medicine, University of Mississippi Medical Center, Jack- 1966 to 2004 on MEDLINE and all years on FORMIS. son, Mississippi. ‡ Department of Medicine, University of Arizona School of Medicine, Articles that concerned anaphylactic (IgE-mediated) or ana- Tucson, Arizona. phylactic-like (resembling anaphylaxis but mechanism un- § AMF Pest Management, Boca Raton, Florida. known) immediate reactions to ant stings or bites were in- ¶ Southwestern Biological Institute, Tucson, Arizona. cluded in this review. Reports of adverse reactions to ʈ Department of Entomology, University of Georgia, Griffin, Georgia. ** Watson Clinic LLP, Lakeland, Florida. different species of ants were used to construct Table 1. Received for publication December 22, 2004. Those reports with documented case histories were used to Accepted for publication in revised form March 3, 2005. construct Table 2. 418 ANNALS OF ALLERGY, ASTHMA & IMMUNOLOGY Table 1. Ants Other Than Imported Fire Ants Reported to Cause reactions to ants have been reported for 10 genera in 6 Adverse Reactions in Humans subfamilies (Table 1). Geographic location Subfamily and species of ant Subfamily Formicinae of (common name) stinging incident These ants do not have a stinger but can spray venom, which contains formic acid and other nitrogenous constituents, into Subfamily Formicinae wounds inflicted with the mandibles.7 We found 1 reported Formica rufa (wood ant) Europe case of anaphylaxis associated with a bite from Formica rufa, Subfamily Myrmeciinae 8 Myrmecia pilosula (jack jumper ant) Tasmania, Australia a widespread species in central Europe (Table 2, case 1). The Myrmecia pyriformis Tasmania, Australia patient’s serum was positive for specific IgE against whole- (bull-dog ant) body extract of F rufa. As in other subfamilies, the formicines Myrmecia forficata (inchman ant) Tasmania are capable of secreting compounds from the mandibular and Subfamily Ponerinae Dufour glands along with venom during an aggressive en- Pachycondyla sennaarensis United Arab Emirates counter.7 The source of the allergen in case 1, however, was (Samsum ant) not identified. Pachycondyla chinensis Korea, Japan Odontomachus bauri Venezuela Subfamily Myrmeciinae (trap-jaw ant) Bull-dog ants belong to the primitive genus Myrmecia, which Hypoponera punctatissima Connecticut are characterized by their aggressive nature, powerful sting, Subfamily Ectatomminae fast movements, and keen vision.9 There are approximately Rhytidoponera metallica (greenhead ant) Australia 120 species, and all are restricted to Australia except one in Subfamily Myrmicinae New Caledonia.9 The jack jumper ant, in the Myrmecia Solenopsis xyloni (southern fire ant) Mississippi, Arizona, California, Texas pilosula species complex, is the most common cause of 10 Solenopsis aurea (desert California allergic reaction. Suburban life has increased their contact 11 fire ant) with humans. In Tasmania, allergic reactions to their stings Solenopsis geminata Okinawa, Guam, occur in approximately 2.7% of the population, almost twice (tropical fire ant) Oahu as often as those to honeybees (1.4%).12 Other species that are Tetramorium spp. South Carolina allergenic include the inchman ant, Myrmecia forficata,12 and Pogonomyrmex barbatus Texas, Oklahoma the bull ant, Myrmecia pyriformis.13 Another species that has (red harvester ant) been implicated is Myrmecia nigrocincta.10 There appears to Pogonomyrmex maricopa (Maricopa Arizona be immunologic cross-reactivity of the venom among differ- harvester ant) 14 Pogonomyrmex rugosus (rough harvester Arizona ent species of these ants. Several deaths have been recorded 15,16 ant) (Table 2, cases 2 to 7). In southeastern Australia, most 13 Subfamily Pseudomyrmecinae stinging incidents occur in backyards. Pseudomyrmex ejectus Georgia, Florida Subfamily Ponerinae (twig or oak ant) Another primitive group is the Ponerinae, which is primarily tropical in distribution. They typically form small colonies with a few hundred individuals.17 The genus Pachycondyla is Three new case reports were documented by 4 of the responsible for most cases of anaphylaxis. Four deaths during authors. Case 12 was documented by Dr Frishman, who was a 4-year period have been attributed to the Samsum ant, contacted as a pest control consultant. In case 22, Dr Suiter Pachycondyla sennaarensis, which is found in Africa and the received an ant by mail from an extension agent in south Arabian Peninsula.18,19 In the United Arab Emirates, allergic Georgia, after its stings caused a severe reaction. Dr Klotz reactions are more common in women, presumably because contacted the attending physician and patient to obtain the they stay primarily at home where the ants are commonly case history. Case 23 was a patient of Dr Price. found both indoors and outdoors in the garden.19 Another species, Pachycondyla chinensis (Table 2, cases 8 RESULTS and 9),20,21 causes adverse reactions in the Far East. The Adverse Reactions From Ants Other Than Imported generic names, Brachyponera (Table 2, case 9)21 and Ecto- Fire Ants momyrmex (Table 2, case 10),22 are synonymous with Pachy- Stinging ants, bees, and many species of wasps are aculeate condyla.23 Unfortunately, in the latter case the ant responsible Hymenoptera. In Aculeata the ovipositor of females has been was not identified as to species. In ant-infested areas of Korea modified into a stinger. The stinger in numerous species of there is a 2.1% incidence of systemic allergic reactions after ants is vestigial or absent. However,