ENVENOMATIONS - Medicine for Mountaineering and Other Wilderness Activities - page 509

northern and central Sierra Nevada, and to occupy the coastal areas of Oregon and Wash-
ington.
In infested urban areas, 30 to 60 percent of the inhabitants are stung by fire ants every
year. Stings are more common among children, on the legs, and during summer. The ant
grabs the skin with powerful mandibles and, if undisturbed, stings repeatedly, twisting its
body so it can reach different sites. Almost everyone stung by an ant develops a wheal-
and-flare reaction—a pale bump that itches and is surrounded by a thin rim of skin that
has turned red. This reaction resolves in about thirty to sixty minutes, but within twenty-
four hours evolves into a sterile pustule (a pimple or small boil). The skin over the pustule
sloughsintwotothreedays.Notherapyiseffectiveforthepustule,butscratchingcanlead
to infection that may require antibiotic therapy.
One-fourth to one-half of the individuals who have been stung develop large local re-
actions that are red, swollen, firm, and “itch like crazy!” In extreme cases, compression of
nerves or blood vessels develops, and a few individuals have required amputation. Eleva-
tion of the extremity, steroid therapy, and antihistamines can largely prevent such extreme
reactions. Topical steroid ointments such as 0.25 percent hydrocortisone, local anesthet-
ic creams, and oral antihistamines reduce the itching associated with more common, less
severe reactions.
About0.5to1percentofstingsarefollowedbyanaphylacticreactions,andanumberof
deaths have resulted. Most of the fatalities occurred in individuals who had been stung less
thanfivetimes.Anaphylacticreactionscanoccurhoursafterasting.Suchreactionsshould
be treated like any other anaphylactic reaction ( Chapter 23: Allergies ) .
Nomethodforcontrollingthepopulationoffireantsoveralargeareaiscurrentlyavail-
able. Avoiding contact with the insects is virtually impossible for individuals who live in
infestedsites.Thosewhodevelopanaphylaxis followingastingshouldconsultaphysician
aboutdesensitization.Whole-bodyextractsoffireants,unlikewholebodyextractsofother
hymenoptera, contain substantial (although variable) quantities of venom and are effective
for desensitization. Thousands of residents of infested areas are receiving such therapy.