Walking Well: Arthropod Stings

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Arthropod stings are serious and most dangerous when they cause severe allergic responses. Arthropods, which inject toxins—either by a tail stinger or other spike or orally—include bees, wasps, hornets, yellow jackets, ants, caterpillars, spiders, ticks, centipedes, millipedes and scorpions (the last three mainly are more of a problem in the Southwest). Stinging events are common on the A.T. and usually result in only transient pain and swelling caused by the injected small molecules. The venom also contains proteins that cause sensitization. However, only an estimated 1 to 2 percent of the population are extremely sensitive to insect venom [Graham, p 1232, 1992] and sting-related deaths are rare, nationally only half the number caused by lightning.

Anaphylaxis is the most severe allergic response to insect stings. It most often affects people sensitized by previous exposure, although others can develop a sensitivity at any time. In sensitive people, as the antibodies respond to the toxic effects of the venom, the body releases histamine and other substances into the system. Anaphylaxis requires immediate treatment since it can cause any or all of the following conditions: a severe skin rash, facial swelling, constriction of the throat resulting in difficulty in breathing, nausea, cramps, anxiety, lowered blood pressure, unconsciousness, shock and even death.

Hikers who have a history of severe reactions to insect stings should be prepared. Treatment includes immediately removing the stinger, taking an antihistamine, and injecting epinephrine (Adrenaline) in the most severe cases. Epinephrine is contained in kits prescribed by doctors. Local treatment includes applying a 1% hydrocortisone ointment (Cortaid, etc.) to the site of the sting and taking analgesics for pain. Oral antihistamines may not "kick in" quickly and local application of a spray (such as Benadryl) may be effective.

Recent medical articles advise victims to remove the bee stinger as rapidly as possible to minimize the amount of injected toxin. Immediately scrape the stinger off, using a knife blade, or credit card, or extract it with fingers or tweezers. Previously, it was thought that using the fingers or tweezers would compress the venom sac and inject more toxin. In experiments on themselves, some researchers have found that the toxin injection was automatic due to rhythmic contraction of the stinging apparatus and unaffected by the method of removal. Speed of removal was the most significant factor in avoiding greater swelling.

Bees can only sting once since the stinger becomes embedded in the victim, while yellow jackets (which have the most painful venom), wasps and hornets can sting multiple times. In all cases it is important to leave the infested area to avoid more stings by the original attacker or its friends because the insect stinging response is a defense against threats to the nest. Removing the threat (i.e.: yourself) is essential. Stinging bees secrete a pheromone that attracts more potential stingers. Watch where you walk. Social wasps nest on the ground and paper wasps nest in trees.

Most deaths are caused by allergic reactions and occur in 15 to 30 minutes after a sting. In adults it would take about 1,000 stings to cause non-allergic death. Children are more vulnerable.

Common ants are relatively unimportant. Imported fire ants are a big problem in some areas of the South. As much as 40 percent of the population of infested urban areas may be stung each year, resulting in 30 deaths from these insects.

Spider bites are generally not severe because their mouth parts are small and can only penetrate skin with difficulty. Black widow spiders and brown recluse spiders may be found in some shelters, latrines and barns especially in the southern areas of the AT. They have venom that can be irritating and even lethal. No first aid measures are of value. Closer to civilization, an ice cube placed on the bite will provide some relief. If more than local symptoms or signs develop, the patient should be hospitalized and antivenin should be considered.

Caterpillars should be regarded as potentially dangerous since several species of moth caterpillars have stinging spines. A trail maintainer in West Virginia reported a very painful reddened outline of a caterpillar (possibly puss moth) on her hand after, leaning against a tree, she pressed her hand to its surface. The sharp sting caused pain in the whole hand and then her arm, together with weakness. The pain lasted several days despite local and systemic treatment, the combination of which was only partially effective. Watch for these larval forms feeding on vegetation. Gypsy moth caterpillars have hairs that cause allergy, a possible problem in areas that are heavily infested.