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INTRODUCTION AND EPIDEMIOLOGY

The phylum Arthropoda is the largest division of the animal kingdom. The phylum includes insects (bees, wasps, hornets, flies, mosquitoes, bedbugs, fire ants, caterpillars, fleas), arachnids (spiders, scorpions, chiggers, ticks), and crustaceans (shrimp, lobsters, crabs). Venomous bites and stings from arthropods are a significant worldwide problem. In the United States, anaphylactic reactions to Hymenoptera stings account for the most fatal arthropod envenomations, although exposures to all arthropods can result in potential emergencies. This chapter discusses the most common and serious arthropod bites, stings, and envenomations. Tick bites are discussed in Chapter 161, “Zoonotic Infections.”

WASPS, BEES, AND ANTS (HYMENOPTERA)

Wasps, bees, and ants belong to the order Hymenoptera. More fatalities result from stings by these insects than by stings or bites by any other insect. There are three major subgroups or “superfamilies” of medical importance: (1) Apidae, which includes the honeybee and bumblebee; (2) Vespidae, which includes yellow jackets, hornets, and wasps; and (3) Formicidae, or ants.

BEES AND WASPS

Honeybees and bumblebees are usually docile, stinging only when provoked. A female honeybee is capable of stinging only once (male bees have no stinger) because its stinger has multiple barbs that cause the sting apparatus to detach from the bee’s body, leading to evisceration and eventual death.

Africanized honeybees, or so-called “killer bees,” are now found in many of the southern and warmer regions of the United States, including Arizona, California, Nevada, New Mexico, and Texas. These bees are hybrids of African bees that escaped from laboratories in Brazil during the 1950s and have successfully spread northward along the coasts and temperate regions of the continent. Their venom is no more toxic than that of their American counterpart, but Africanized hybrid honeybees are much more aggressive and more likely to attack in swarms. An attack from Africanized bees can lead to massive stinging, resulting in multisystem damage and death from severe venom toxicity.1,2

Most of the allergic reactions reported each year due to Hymenoptera occur from wasp, hornet, and yellow jacket stings. These arthropods typically nest in the ground (yellowjackets) in trees and shrubs (hornets) or in walls (wasps). They have volatile tempers and may be disturbed by work taking place around the nest. As with bees, only the females have adapted a stinger from the ovipositor on the posterior aspect of the abdomen. Although vespids also possess barbed stingers, they can withdraw their stingers from the victim, which permits multiple stings.

Hymenoptera venom contains several components.3 Although histamine is one component, other substances are now recognized as more important. Melittin, a known membrane-active polypeptide that can cause degranulation of basophils and mast cells, constitutes >50% of the dry weight of bee venom. Protein enzymes such as phospholipase and hyaluronidase may account for most systemic reactions.4,5 Because all Hymenoptera ...

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