Fire ants (40), indigenous to tropical America, were imported into Alabama in the United States in 1918, but now are seen in such diverse locales as
Australia and Korea (41). In endemic areas, such as the southeastern United States, fire ants represent the leading cause of insect hypersensitivity (42) and, perhaps, of anaphylaxis (43). The 2 to 5 mm, red-brown ants, Solenop-sis richteri and Solenopsis invicta, nest in up to 50-cm diameter mounds bearing up to 200,000 ants with tunnels to the outside world that can extend to 25 m from the mound center. Up to 10,000 stings can be inflicted on an individual who disturbs the mounds (44). The stinging ant first bites into the skin before pivoting about its head to deliver multiple stings through a stinging apparatus at its caudal end. The venom, a necrotizing toxin containing solenamine, produces a wheal and flare reaction within 30 minutes that resolves 30 minutes later; a sterile pustule forms about a day later, for which there is no effective treatment (45), but it does resolve on its own a few days later if undisturbed; bandage can help prevent excoriation. Steroid creams can help with allergic reactions. Topical antibiotics should be applied if local infection is suspected.
Systemic reactions occur in 16% and anaphylaxis in 2% of patients. The onset occurs within 45 minutes of a sting. It can include urticaria, chest tightness, pruritis, dysphagia, abdominal cramps, nausea, vomiting, diarrhea, wheezing, the changes of anaphylaxis (described later), syncope, convulsions, confusion, mononeuropathy and seizures (46-48). Therapy is directed towards the particular symptoms and signs the patient has. Immunotherapy is in its early stages but shows great promise (49,50).
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