Insect stings

[GarryDrold]

Stinging insects are members of the order Hymenoptera of the class Insecta. Hymenoptera venoms cause local toxic reactions in all people and allergic reactions only in those previously sensitized. Severity depends on the dose of venom and degree of previous sensitization. Patients exposed to swarm attacks and patients with high venom-specific IgE levels are most at risk of anaphylaxis; many children never outgrow the risk. The average unsensitized person can safely tolerate 22 stings/kg body weight; thus, the average adult can withstand gt; 1000 stings, whereas 500 stings can kill a child.
Unexpectedly large numbers of people seek medical attention for stings and their complications after hurricanes and possibly other environmental disasters.
Major Hymenoptera subgroups are

Apids (eg, honeybees, bumblebees)
Vespids (eg, wasps, yellow jackets, hornets)
Formicids (eg, nonwinged fire ants)

Apids usually do not sting unless provoked; however, Africanized honeybees (killer bees), migrants from South America that reside in some southern and southwestern US states, are especially aggressive when agitated. Apids typically sting once and dislodge their barbed stinger into the wound, introducing venom and killing the insect. Melittin is thought to be the main pain-inducing component of the venom. The venom of Africanized honeybees is no more potent than that of other honeybees but causes more severe consequences because these insects attack in swarms and inflict multiple stings, increasing the dose of venom. In the US, bee stings cause 3 to 4 times more deaths than do venomous snakebites.
Vespid stingers have few barbs and do not stay in the skin, so these insects can inflict multiple stings. The venom contains phospholipase, hyaluronidases, and the antigen 5 protein, which is the most allergenic. Although vespids also avoid stinging unless provoked, they nest close to humans, so provocative encounters are more frequent. Yellow jackets are the major cause of allergic reactions to insect stings in the US.
Fire ants are present in the southern US, particularly in the Gulf region, where in urban areas, they may sting as many as 40% of the population, causing at least 30 deaths/year. There are several species, but Solenopsis invicta predominates and is responsible for an increasing number of allergic reactions. The ant bites to anchor itself to the person and stings repeatedly as it rotates its body in an arc around the bite, producing a characteristic central bite partially encircled by a reddened sting line. The venom has hemolytic, cytolytic, antimicrobial, and insecticidal properties; 3 or 4 small aqueous protein fractions are probably responsible for allergic reactions.