Fire ant

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Code: i70
Latin name: Solenopsis invicta
Source material: Whole insect bodies
Family: Myrmicidae

Insect

An insect, which may result in allergy symptoms in sensitised individuals.

Allergen Exposure

The name ‘fire ant’ comes from the pain that occurs soon after stinging. Fire ants are a variety of stinging ants with over 285 species worldwide. Solenopsis species are found over most of the tropical and temperate parts of the world, including Central Europe, Central Asia, Pacific Asia, Africa, Australia and the Pacific Islands. They have several common names, including ginger ants, tropical fire ants, and red ants. However, in this context ‘fire ant’ refers specifically to the species Solenopsis invicta.

In the USA, the term ‘imported fire ant’ has been used to distinguish the species Solenopsis invicta and S. richteri (black fire ant) from the native North American species of fire ant, S. xyloni and S. aurea, and from the tropical fire ant, S. geminata. (1)

Unlike many other ants, which bite and then spray acid on the wound, fire ants bite only to get a grip and then sting, injecting a toxic alkaloid venom called solenopsin, a compound from the class of piperidines. The ant’s name comes from the pain that manifests soon after stinging: a sensation similar to what one feels when burned by fire. The ant is aggressive; it bites the victim with its mandible, arching its back and inserting the stinger, located on the ant’s back, on average seven or eight times in a circular pattern. (1)

Most fire ant species do not bother people and are not invasive; however, Solenopsis invicta, a native of Argentina, Paraguay, and Brazil (known in the USA as the red imported fire ant) is an invasive pest in many areas of the world, notably the United States, Australia, the Philippines, China and Taiwan. S. richteri and S. invicta were first introduced into the United States from South America unintentionally, in 1918 and the 1930s, from cargo ships that docked at the port of Mobile, Alabama. They came to infest the majority of the southern and south-western United States, and the southern half of the eastern coast down to Puerto Rico. (1, 2, 3, 4) Fire ants have also been found in parts of Australia and New Zealand. (5, 6) They also inhabit numerous islands of the West Indies, including the Bahamas, Virgin Islands, Antigua, Providenciales, and Trinidad; and reportedly also in China, Malaysia, Taiwan, and Mexico. (1, 7)

Recently S. invicta has been discovered in the Guangdong Province of China, and subsequently in Hong Kong. (8)

Another ant species reported to cause anaphylaxis in the United States belongs to the genus Pogonomyrmex. (9)

In addition to Solenopsis, other species of ants are known to cause anaphylaxis in various parts of the world: Pachycondyla chinensis and Pachycondyla solitaria in Korea (10) (the former also found in Japan and China (11)), jack jumper ant (Myrmecia pilosula) in Australia, (12) and the red harvester ant (Pogonomyrmex) in Europe. (13)

Fire ants nest in the soil, often near moist areas such as river banks, pond shores, watered lawns and highway shoulder. Usually the nest will not be visible, as it will be built under objects such as timber, logs, rocks, or bricks. If there is no cover for nesting, dome-shaped mounds will be constructed; when this occurs, a typical fire ant colony produces large mounds in open areas, and feeds mostly on young plants, seeds, and sometimes crickets. The mounds can be found in lawns, beside walks and in roads in fields. (14)[ Fire ants are drawn to electrical fields, infesting electrical wiring, transformers, etc. (15)

Allergen Description

The venom of the fire ant is unique. It is composed principally of 2-methyl-6-alkylpiperidines. Some of these alkyloids are found nowhere else in the animal or plant world. (16) Fire-ant venom is unique because of its low protein content and high concentration of piperidine toxins, consisting of 90-95% water-insoluble alkaloids. (17)

Each S. invicta sting transfers 0.04 to 0.11 µL of venom and 10 to 100 ng of protein. (18) The alkaloid portion consists primarily of 2,6 di-substituted piperidines (water-insoluble n-alkyl and n-alkenyl piperidine) that have cytotoxic, hemolytic, antibacterial, and insecticidal properties. (14, 19) These alkaloids produce a sterile pustule but do not induce IgE responses. (1) The structure of these alkyloids has been shown to have an evolution of longer and more saturated side chains, with side-chain saturation increasing with worker age. (20, 21)

The soluble proteins responsible for allergic reactions comprise 0.1% of the venom weight. (15, 22) Venom protein concentrations may be 100 times higher in summer than in other seasons; this is said to explain the disparity between the prevalence and severity of summer and winter stings. (17, 23)

Four major protein allergens have been isolated and characterised: (24, 25, 26, 27)

Sol i 1, a 37 kDa protein, a phospholipase comprising 2-5% of the venom protein. (24, 28, 29, 30, 31, 32, 33)

Sol i 2, a 26 kDa protein, comprising 67% of the venom protein. (24, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38)

Sol i 3, a 24 kDa protein, a member of the antigen 5 venom family, comprising 20% of the venom protein. (24, 28, 29, 31, 32, 33, 38, 39, 40, 41, 42, 43)

Sol i 4, a 13 kDa protein, comprising 9% of the venom protein. (28, 29, 31, 32, 33, 35, 38, 39)

Sol i 1, venom phospholipase, related to wasp-venom phospholipases. (30)

Sol i 3 is a member of the antigen 5 family of venom proteins, but does not show any significant cross-reaction with antigen 5 from other vespids. (14)

Sol i2 and i4 are not similar to any other known proteins. Sol i 4 has 35% identity with Sol i 2 but does not cross-react immunologically. (14)

S. richteri venom has very similar proteins corresponding to Sol i 1, Sol i 2, and Sol i 3, but does not have a protein corresponding to Sol i 4. (14,15)

Potential Cross-Reactivity

Cross-reactivity is reported with venom from other Solenopsis species (44) as well as with venoms from other Hymenoptera. (38)

Cross-reactivity between family members appears to be common, as described in a report of a group of patients who reacted with any of the three species of fire ants (S. richteri, S. xyloni, and S. aurea), and were shown to be RAST-positive to S. invicta and S. richteri venom, as well as skin-test-reactive to S. invicta whole-body extract. Four of the patients experiencing reactions caused by S. xyloni, and both patients experiencing reactions caused by S. geminate, were previously sensitised to S. Invicta; the clinical reactions probably resulted from immunologic cross-reactivity. (24) The close family cross-reactivity relationship has been confirmed in laboratory studies, where the structures of S. richteri allergens were shown to have a high degree of similarity to S. invicta allergens. The Sol 2 allergens are less related to each other than either the Sol 1 (phospholipase AB) or Sol 3 (antigen 5) allergens. Patients sensitised to native species of fire ants reacted primarily to the Sol 1 and Sol 3 allergens, whereas those originally sensitised to S. invicta also reacted significantly to the Sol 2 and Sol 4 allergens. The authors concluded that S. invicta ‘imported’ fire ant venom extracts were probably sufficient for diagnosis for the four species examined. (24)

Interestingly, although the venom allergens of S. invicta and S. richteri appear to be allergenically similar, a similar allergen to Sol i 4 is absent from S. richteri. (32)

Sol i 1 cross-reacts with honeybee and vespid (yellow jacket) venom, but other fire-ant venom proteins do not demonstrate immunologic cross-reactivity. This accounts for the clinical observation that some individuals have anaphylaxis to their first known fire ant sting. (20) Sol i 1 has a 31-32% identity with yellow jacket phospholipases. (22, 30, 45)

Sol i 3 shows 44-50% homology but only minimal conserved areas in common with vespid (yellow jacket) group 5 allergens, which explains the lack of observed IgE cross-reactivity; (22, 40) although other authors have reported the cross-reactivity to be variable, and seen primarily with yellow jacket. (46)

Pac c 3, a major allergen of Pachycondyla chinensis (samsum ant), has 54% homology with Sol i 3 from fire ant, (41, 47) although one author reported the cross-reactivity to be minimal. (11)

This is supported by a study of P. chinensis venom that found it to be possibly cross-reactive with bee venom, but not with imported-fire-ant venom. (48)

Significant cross-reactivity has also been demonstrated between the venom of the common striped scorpion (Centruroides vittatus) and imported fire-ant whole-body extract. The authors point out that a high sensitisation rate to imported fire-ant venom in endemic areas may therefore be a risk factor for subsequent immediate reactions to an initial scorpion sting. (49)

Clinical Experience

a. IgE-mediated reactions

Four possible reactions are seen after fire-ant stings: local reactions; regional reactions; systemic anaphylactic responses; and, less commonly, delayed-type hypersensitivity. (15, 50, 51)

Stinging immediately results in an immediate and intense burning (‘fire’) and itching at the site of a sting, resulting in an erythematous flare followed by a wheal. Within 4 hours, a vesicle containing clear fluid begins to form; followed by the formation of a sterile pustule within 24 hours, surrounded by a red halo or a large erythematous, painful area, (3) the pain from which frequently persists up to 72 hours. (52) The sterile pustules are typically 1-3 mm in diameter and appear due to the alkaloid components of the venom. (1, 14, 53) The material in the vesicle is necrotic, and it should be left intact to prevent secondary infection. (52) Excoriation of pustules risks superinfection. (15) Acute bullous skin reactions have been reported. (54)

Seventeen to 56% of stung subjects have initial venom-specific IgE-mediated wheal-and-flare responses, and these evolve over several hours, typically peaking in 12-48 hours; into a second phase of localised swelling involving pruritic oedema, induration, and erythema that may persist 24 to 72 hours. (1, 14, 15) Large local reactions may be caused by a late-phase IgE-mediated reaction, and the risk of a subsequent sting resulting in a systemic reaction may be as high as 5-10%. (55, 56)

Stings occurring during the off-season (i.e. the winter months) may go unnoticed until the local reaction develops. Severity of reaction may also be influenced by the season. This may reflect the seasonal variations in IFA venom protein concentration, as venom protein concentrations may be 100 times higher in summer than in other seasons. (15, 23) A study reported that 51% of systemic allergic reactions to fire ant stings occur in summer and 19% in spring. (23)

Individual variation in the degree of hypersensitivity to fire-ant venom occurs, with over 5 000 stings without untoward effect having been reported as a complication of alcoholism, (57) and a new-born experiencing near-fatal envenomation from over 5 000 stings. (58)

Serious systemic allergic reactions resulting in life-threatening – and even fatal – anaphylaxis occur in 0.6% to 16% of fire-ant-sting patients. (14, 17, 15, 22, 59, 60, 61, 62) Symptoms can manifest as generalised pruritus, headache, flushing/erythema, generalised urticaria, angioedema, laryngeal oedema, bronchospasm, hypotension or loss of consciousness, and resultant cardiovascular collapse and respiratory failure. (6, 14, 15, 17, 63, 64, 65, 66) Anaphylaxis may occur hours after a sting. (15) Neurologic sequelae following an IFA sting (including seizure and neuropathy) have been reported. (67, 68)

Deaths appear to involve predominantly males, with a wide age-range, from infancy to 65 years of age. Most deaths are caused by fewer than five stings. (20) Systemic reactions usually occur in individuals previously sensitised to a fire-ant sting, (14, 17) although subjects with no previous exposure have been reported who experienced anaphylactic reactions after their first sting. (14) Most of these subjects appear to have been previously sensitised to yellow jacket (Vespula) venom. (14, 15)

A survey of 29 300 physicians conducted in 1989 reported that 83 fatal reactions (32 confirmed) were recorded following stings from fire ants. (65, 69 )The number of deaths per year was probably underestimated, as many cases of anaphylaxis may not be diagnosed or reported; (1) and the number has undoubtedly increased over the years, as fire ants have extended their habitat in various parts of the world. In an earlier (unpublished) survey from Mississippi, Georgia, and Alabama, reporting on individuals treated for fire-ant stings from 1969 (9 422 cases) to 1971 (12 478 cases), 154 cases of anaphylactic shock and 17 deaths were recorded. (Triplett cited in 20)

Case reports are illustrative.

An 18-month-old male child playing quietly suddenly started crying. Parents noticed 10-20 red ants, on all four limbs. After 15 minutes they found the child to be drowsy, not responding to oral commands, and his body cold. Eight hours after admission he developed multiple pustules on both upper and lower limbs. The pustules gradually turned into scabs, and disappeared after 4 days. (70)

Fatal anaphylaxis was experienced by a 3-month-old female following a fire-ant sting that occurred indoors at a daycare facility. The caregiver had heard the child crying, but attributed this to colic. The child was found apnoeic and covered with ants. A RAST test was positive for S. richteri venom, but negative for S. invicta. The ants were identified as the closely-related species S. xyloni, a native fire ant also endemic to the south-western United States. (71)

An unusual response to fire-ant sting associated with IgE-mediated sensitisation was described in a 5-year-old male who developed unusual bullous scarring lesions after fire-ant stings, on two separate occasions. No evidence for infection, underlying skin disease or systemic disease that would predispose this patient to such an exaggerated and atypical response was found. Skin-prick testing was positive for fire ant whole-body extract. There was no evidence of bullae after skin-prick testing. (54)

A 31-year-old woman experienced anaphylaxis following multiple IFA stings on her feet, developing itchy palms, light-headedness, and dyspnoea within 10 minutes, as well as hypotension. A skin-prick test to IFA whole-body extract was positive 6 weeks after the reaction. (72)

An unusual case of anaphylaxis after being stung by S. invicta ants while handling wood that had been imported from South America was described in a 27-year-old woman. Serum-specific IgE for S. invicta was 5.28 kU/L and negative for A. melifera, Ves v 5 and Pol a 5. Serum IgE to Sol i 2 was raised. The authors surmised that she had probably been sensitised inadvertently by having been stung previously by red fire ants. Intradermal skin tests with Hymenoptera venom (Vespula vulgaris, Polistes species, Apis melifera) were negative, suggesting that cross-reactivity was not the cause of primary sensitisation. Skin tests were not performed with fire ant because extract was not available. (73)

A 28-year-old Caucasian female presented with shortness of breath, generalised pruritus and tachycardia after a single fire-ant sting. Six weeks prior to presentation she had developed a large swelling and pain in her left leg (ankle to knee), where she had been stung by over 25 ants. Three weeks later, before her initial visit to the clinic, she experienced skin flushing, generalised pruritus and urticaria, shortness of breath, chest tightness, and tachycardia, after a single ant sting. On all three occasions, she developed the typical fire-ant pustules at all sting sites over several days. A skin-prick test for fire ant was positive. (1)

A report of a 30-year-old woman who died of anaphylaxis following multiple fire-ant stings stated that post-mortem blood samples were positive for imported fire-ant-venom-specific IgE antibodies (5 654 ng/ml) and tryptase (12 ng/ml). (65)

Another study reported 2 cases of grand mal seizures associated with the sting of the fire ant. The first patient suffered numerous stings without evidence of systemic reactions prior to the onset of the seizure. The second patient had manifestations of anaphylaxis prior to the occurrence of seizure. In both cases, the onset of seizures was delayed. (68)

A 19-month-old child developed a characteristic, localised cutaneous reaction at the sites of numerous stings after disturbing an ant mound. He experienced no secondary complications, and his pustular lesions resolved with conservative treatment. (74)

A 49-year-old female presented for evaluation of generalised pruritus and near-syncope immediately following 2 fire-ant stings on her left foot and 8 fire-ant stings on her left hand, while gardening. The characteristic Fire ant-induced pustules developed on her foot and hand. One month prior to being stung 10 times, she was stung twice on her left foot while walking barefoot and experienced a focal motor seizure of the right lower extremity, which progressed to a generalised grand mal seizure. Eight weeks following the anaphylactic reaction, her fire-ant whole-body intradermal skin test was positive. She was placed on IFA allergen vaccine immunotherapy. (63) The authors had previously reported neurologic sequelae from fire-ant stings in 5 other subjects: 4 experienced anaphylaxis, 3 of whom had grand mal seizures and 1 a focal motor seizure. One patient experienced a transient right radial mononeuropathy after being stung multiple times on the right arm, but did not develop anaphylaxis. 67, cited in 63)

A number of unusual case reports of adverse reactions to fire ant have been reported: a near-fatal reaction by an infant playing in the backyard, a pharmacist working indoors in a hospital setting under a ceiling ventilation duct, (75) anaphylaxis in an infant, (71) and placental abruption and intrauterine death following a fire-ant sting. (76)

Sensitisation to fire ant – i.e. raised specific fire-ant IgE – has been noted to be 1.7 times more common in adults living in an endemic area than specific IgE for other allergens associated with potentially fatal anaphylaxis. This suggests that IFA may pose the greatest risk of anaphylaxis for adults residing in IFA-endemic regions. (77) Between 30% and 60% of subjects in endemic or infested urban areas are stung by fire ants each year. (15, 18, 53, 78) One survey reported stings in 89% of subjects or immediate family members per year. (79, cited in 15)

Unexposed individuals are rapidly sensitised to fire ant when arriving in an endemic area; a study reported 55 (51%) of 107 previously unexposed subjects being stung within 3 weeks of arrival in an endemic area, and 8 (16%) developed fire-ant-venom-specific IgE antibody. (80) Fifty-three (96%) reported a pustule or a small local reaction at the sting site; one (2%) reported an isolated large local reaction; and none reported a systemic reaction. At the 3-week follow-up, skin-test and RAST conversions occurred in seven subjects (13%) and in one subject (1.8%) respectively. The authors pointed out that even brief exposure to fire-ant-endemic areas results in significant sting rates and concurrent rapid development of IFA-specific IgE in 16% of stung subjects. (80)

A particular and neglected area of concern is that though fire ants were once considered to be an outdoor pest, sting attacks now occur indoors, affecting the very young and the very old in particular, due to the decreased mobility of these age extremes. (71, 81) Fire-ant stings have occurred in health facilities and nursing homes. (78, 84, 82, 83, 84) The exact cause of this increasing phenomenon is unclear; but it is clear that immobilised individuals are at risk for multiple stings when fire ants are present in that environment. (71, 78, 85, 86) Frail elders (87) and cognitively impaired patients are at risk, and health-care providers and administrators in fire-ant-endemic areas need to be aware that the presence of fire ants in hospitals and nursing homes represents a hazard. (83) The establishment of an intact fire-ant colony within an inhabited dwelling has been described. (78)

To test the hypothesis that additional indoor sting attacks by fire ants were occurring, particularly to frail, elderly people, the archives of 182 US newspapers in fire-ant-endemic areas in 10 states were searched. Ten additional cases of indoor fire-ant sting attacks were reported in local newspapers, giving a total of 16 attacks on adults and four on infants. Most adult attacks occurred in long-term care facilities, but three involved hospitalised patients. Morbidity ranged from nightmares to death in seven adults. One of the infants died, and two suffered long-term morbidity. Six of the 20 sting victims died within 1 week of the attack. Seven of the 10 attacks reported in newspapers did not result in significant medical consequences, compared to only two of the 10 attacks in previously published reports. (87)

It is also self-evident that certain occupations may be at higher risk for fire-ant stings. (88)

A number of studies have given insight into the prevalence and frequency of fire-ant sting and subsequent sensitisation.

Importantly, fire-ant hypersensitivity may be the most common Hymenoptera hypersensitivity found in some endemic areas: in one study, a 51% sting attack rate among subjects in an endemic area during 3 weeks of summertime exposure was reported, (80) accounting for up to 42% of all cases of Hymenoptera stings in endemic areas. (89)

A study from South Carolina reported that fire ants were firmly established in all 46 counties. In 1998 there were an estimated 660 000 cases in the state, of which approximately 33 000 sought medical treatment. 57% of treatment sought was for children under 15 years of age. (61)

The prevalence of detectable IgE to fire-ant venom (0.1 kUa/L) in 183 children living in an endemic region of the south-eastern United States was demonstrated to occur in in 7.1% of 0- to 1-year-olds, 57.1% of 2- to 5-year-olds, and 64.4% of 6- to 10-year-olds. Almost 40% had been stung by a fire ant in the previous month, with 23.9% receiving more than 6 stings per month. The authors concluded that in endemic areas, the onset of sensitisation to fire-ant venom occurs in the first years of life, with more than half of the children demonstrating sensitisation by 2 to 5 years of age; and that when stung, they often receive multiple stings. (90)

A study of allergic sensitisation to imported fire ants, yellow-jacket venom and peanut in 145 unselected children, 7-18 years of age, from a fire-ant infested area in the USA, found that the prevalence of fire-ant-specific IgE (70/145, 48%) was significantly higher than to yellow-jacket venom (11/145, 7.6%) or to peanut (16/145, 11%). Fire-ant-specific IgE ranged from 0.35 to 68.8 kAU/L. The prevalence of fire-ant-specific IgE in children from Augusta was higher than in local adult blood donors (48% vs 17%). Only 10% (7/70) of fire-ant positive children were also sensitive to yellow-jacket venom. (77, 91)

A retrospective study reviewing all patients seen in a venom clinic at a large teaching hospital in the USA reported that of the 703 patients evaluated between 1985 and 1995, 515 (73%) had reactions consistent with systemic anaphylaxis for which a determination of specific IgE was appropriate. Fire ants were responsible for 42% of the visits to the clinic and accounted for 59% of the total immunotherapy that was begun in this endemic area. (89)

In 1989, members of the American Medical Association in 13 southern states of the USA were surveyed to assess the magnitude of the medical problems caused by fire-ant stings. Of the 29 205 physicians surveyed, 2 022 (7%) reported treating approximately 20 755 patients annually for reactions to IFA stings. Most patients were treated for local reactions, but 413 (2%) required treatment for life-threatening anaphylaxis. (59)

Published in the same year were the results of a physician questionnaire conducted by the American Academy of Allergy and Immunology. From 29 300 physicians surveyed, reports of 83 fatal and two near-fatal fire-ant-sting reactions were received. Most anaphylactic deaths were reported from Florida (22) and Texas (19). (69)  

Although the majority of studies pertaining to fire-ant stings have been reported in the USA, a few indicate the presence of fire-ants elsewhere. Of 31 consecutive cases referred to a Singaporean immunology/allergy outpatient service, the causative insect was identified as honeybee (n=12), ant (n=4), wasp (n=3) and fire ant (n=2). Ten patients were unable to identify the causative insect. (92)

An Australian study evaluated 1 787 patients presenting with adverse reactions to insect stings or bites over a 17-year period until 1997, of which 111 (6%) nominated various types of ants. Fire ant was only identified by one individual, with 48 not being able to identify the ant. (93)

Authors have suggested that subjects without a clinical history of allergic reactions to IFA should not be tested, because of the high degree of asymptomatic IgE production in an exposed population. Skin-test reactivity among control subjects with no history of IFA hypersensitivity ranges from 8% to 42% with WBV and 8% to 29% with venom. (9, 27, 94, 95)

Among adults with a history of fire-ant exposure but no systemic reaction, 24% were RAST-test positive despite a negative history of insect allergy. (38) Similar results were obtained in a study in which 29% of non-allergic control patients had a positive skin-test to both fire-ant whole-body extract and fire-ant venom. (95) In the same study, 30% had a positive RAST to fire-ant venom. In light of these findings, the authors concluded that routine evaluation for IgE to imported fire ants should be discouraged if the history is not suggestive of an allergic reaction. They also concluded that skin testing is generally the preferred initial test in the evaluation, but if negative and the history is suggestive of fire-ant sensitivity, repeat skin-testing and/or in vitro testing should be done. (1, 55, 96)

While venom is more accurate for skin testing, whole-body extract has been reported to be adequate. (97) Venom RAST has proved to be superior to whole-body venom RAST in several studies because its active material is not diluted by allergenically inactive body substances. (14, 17) In contrast to most whole-body venom RASTs, the ImmunoCAP (®) was reported to bind 3 times more protein than cellulose disk systems yielding whole-body venom-specific IgE results similar to venom RAST and ELISA. (17) Venom CAP assays outperform whole-body CAP assays. (98)

Immunotherapy has been used to treat fire-ant allergy since the 1970s. (94, 99, 100) Because of the high frequency of stings in endemic areas, fire-ant immunotherapy can be considered for children, even if they have only experienced a cutaneous reaction. (55) A number of studies report the benefits. For example, of 65 subjects treated with fire-ant whole-body venom immunotherapy, 47 (72%) unexpectedly sustained fire-ant stings and only 1 resulted in anaphylaxis. None of the 31 subjects who received a single fire-ant sting under direct observation had anaphylactic reactions while receiving maintenance immunotherapy. Of 11 fire-ant-allergic subjects in the control group who declined immunotherapy, 6 had unexpected stings and all 6 had anaphylactic reactions. (101)

However, a study evaluating 3 commercial vaccines demonstrated significant variability in antigenic content and potency. (26) Furthermore, the practice of immunotherapy is not uniform, and nor are the dosages required. Members of the American College of Allergy, Asthma & Immunology practising in fire-ant-endemic states were surveyed regarding fire-ant immunotherapy. Of 329 of 879 (37.4%) surveys returned, 81% of respondents had evaluated patients with imported fire ant allergy; of which 96.7% were using immunotherapy to treat the fire-ant allergy. A wide range of maintenance dosages were prescribed. Systemic reactions to stings while on maintenance immunotherapy were reported by 19%. (100)

A two-day rush protocol with fire-ant whole-body extracts has been described. (102)

b. Other reactions

Seizures and mononeuritis have also been reported after fire-ant stings. (68) Serum sickness, nephrotic syndrome, and worsening of pre-existing cardiopulmonary disease have also been described. (84, 103)

Eosinophilic fasciitis following a fire-ant sting has been reported. (104)

Acute renal failure as a result of rhabdomyolysis subsequent to extensive fire-ant stings was reported in a 59-year-old patient. (105) A 3-year-old child developed idiopathic minimal-change nephrotic syndrome approximately 2 weeks after being stung by fire ant on the legs, scrotum, and penis. Symptoms included oedema of the face and extremities. (103)

An elderly patient presented with hand-foot syndrome (HFS) following multiple fire-ant stings to her lower extremities. Both hands and both feet were red, swollen, and mildly tender. HFS was initially reported in association with acute crisis in sickle-cell anaemia and thalassemia, and more recently as a common toxicity of chemotherapy administration. (106)

Cutaneous sporotrichosis, also known as ‘Rose gardener's disease’, is an uncommon infection of the fungus Sporothrix schenckii, and is usually reported as sporadic cases resulting from small cuts and abrasions to the skin. This case report describes such a case, but as a result of multiple jabs acquired from fire-ant stings. (107)

A neurologically compromised child experienced corneal injury as a result of fire-ant stings. (108)

Compiled by Dr Harris Steinman, harris@allergyadvisor.com 

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As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.