Health Threats to School Children from
Stinging Insects
Jerome Goddard, Ph.D.
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Medical Importance. Wasp, bee, yellowjacket, and fire ant stings are serious health considerations for school children in two primary ways: 1) the direct effects of stings -- pain, itching, swelling, etc., and 2) the indirect effects such as allergic reactions to the venom.1 Direct effects are bad enough, with many children experiencing severe pain and localized swelling after an insect sting.2,3 In others, the direct effect may be even worse with extensive swelling that may be debilitating for days or weeks (termed a large local reaction). Indirect effects of stings -- primarily allergic reactions -- vary from mild systemic (all over the body) reactions such as hives, itching, runny eyes and nose, and wheezing, to severe systemic reactions such as sudden swelling of the respiratory tract, crash in blood pressure, collapse and death within 15-30 minutes.4,5

Contrary to what people think, there are more deaths each year in the U.S. from bee and wasp stings than from snake bites.6 In addition, fire ants have increasingly become a costly medical threat to adults and children in institutions, schools, and day care centers.7-11 For example, in 1998, there were an estimated 660,000 cases of fire ant stings in South Carolina, of which approximately 33,000 sought medical treatment for an estimated cost of $2.4 million.12

Biology of the Pest Species Involved. Paper wasps (including yellowjackets and hornets) build their nests in protected places such as hollow trees, thick bushes, holes in the ground, and the like. The problem is they often build them under the eaves of human dwellings, in wall voids or in attics. Paper wasps begin their nests in the spring with a single mated female wasp (queen), and gradually enlarge the nest, producing more and more worker wasps until winter kills most of them. Accordingly, the worst problems with paper wasps occur in late summer and early fall (unfortunately, this coincides with the start of school). Paper wasps will aggressively defend their nest when disturbed, stinging repeatedly (honey bees sting only once; paper wasps can sting multiple times).

Honey bees (including both the European variety and the newly arrived "killer bee") build their nests in hollow trees, but may also build nests in wall voids. They do not construct a paper nest, instead making a waxy, comb-like structure. In addition, honey bees can overwinter -- cold weather does not kill the hive. Accordingly, a honey bee hive could remain inside a wall for several years. Honeybees also aggressively defend their nest when disturbed. Interestingly, killer bees are no bigger in size or more poisonous than regular honey bees -- only more aggressive. They are more easily alarmed, more of the hive emerges to chase intruders, and they chase intruders much further.

Fire ant stings can even be more serious than bee stings. There are some native fire ants in the U.S., but the imported ones are the worst pests. At least 300 million acres in the U.S. are now infested. Imported fire ant sting aggressively and inject a necrotizing venom to paralyze or kill their prey. The ants characteristically boil out of their mounds in great numbers at the slightest disturbance. Worker imported fire ants attach to the skin of their victim with their mandibles and lower the tip of their abdomen to inject the stinger forcefully; therefore, fire ants both bite and sting, but their stings cause the subsequent burning sensation and wheal. As is the case with any stinging insect, hypersensitivity to fire ant venom may result in severe allergic reactions from just a few stings.

Outdoors, fire ants are best recognized by the appearance of their mounds, which are elevated earthen mounds 3 to 36 inches high surrounded by relatively undisturbed vegetation. In some areas, there are as many as 300-400 fire ant mounds per acre of land, greatly interfering with any outdoor activity. But fire ants may be present in an area even in the absence of visible mounds, because some soil types make mound building difficult. In addition, foraging tunnels 50 to100 feet long are used by workers to collect food for the colony. Children at play may not see these feeding trails and inadvertently get into them. Foraging tunnels are excavated just below the soil surface and extend outward from the mound in all directions. Worker ants travel through these tunnels, emerge from an opening, and search for a food source. Once a food source is located, the foraging worker returns to the tunnel laying a trail of pheromone for other worker ants to follow.

Control Options and Health Effects from Non-use of Pesticides. Paper wasp nests can be mechanically removed (knocked down), especially early in the spring. However, there are obviously some health risks to the person doing the nest removal. A few of the "green" pesticides or other products may also work on paper wasp nests. For example, a soap/water mixture does effectively kill wasps and bees. Nonetheless, there are many instances in which traditional pesticides are needed. Some of the synthetic pyrethroids, packaged as long-range sprays, provide instant knockdown of wasps, hornets, yellowjackets, and bees. In addition, insecticidal dusts are extremely effective tools in controlling hard-to-reach wasp or bee nests in wall voids. Fire ants pose a different problem, being extremely difficult to control without a combination of insecticidal baits (broadcast in the school yard) and individual mound treatments using traditional, residual insecticides. In a recent study of health effects from fire ant stings, the authors (all physicians) recommended pesticidal control of fire ants according to Clemson University Cooperative Extension Service guidelines.12 Alternative, non-pesticidal control measures were mentioned in the official Extension Service guidelines, but were said to be "not very effective."

If traditional pesticides are not available to pest control personnel for the removal of wasp, ant, or bee nests in/around schools, then successful elimination of the nests -- and their associated health risks -- will be extremely difficult, if not impossible. Pesticides should be considered as important "public health tools" in the removal of such pests. Failure to have such tools available will ultimately lead to children being exposed to stinging insects, and possible liability on the school's part for not having provided a safe, pest-free environment.

References
1. Goddard J: Physician's Guide to Arthropods of Medical Importance. 3rd ed. Boca Raton, FL: CRC Press, 2000.

2. Keegan HL: Some medical problems from direct injury by arthropods. Inter Pathol 1969; 10: 35-45.

3. Alexander JO: Arthropods and Human Skin. Berlin: Springer-Verlag, 1984.

4. Kunkel DB: The sting of the arthropod. Emerg Med 1996; (May 1996 Issue): 135-141.

5. Reisman RE: Insect stings. N Engl J Med 1994; 331: 523-527.

6. Parrish HM: Analysis of 460 fatalities from venomous animals in the U.S. Am J Med Sci 1963; 245: 129-145.

7. deShazo RD, Williams DF, Moak ES: Fire ant attacks on residents in health care facilities: a report of two cases. Ann Intern Med 1999; 131: 424-429.

8. deShazo RD, Butcher BT, Banks WA: Reactions to the stings of the imported fire ant. N Engl J Med 1990; 323: 462-466.

9. deShazo RD, Banks WA: Medical consequences of multiple fire ant stings occurring indoors. J Allergy Clin Immunol 1994; 93: 847-850.

10. Levy AL, Wagner JM, Schuman SH: Fire ant anaphylaxis: Two critical cases in South Carolina. J Agromed 1998; 5: 49-54.

11. Kemp SF, deShazo RD, Moffitt JE, Williams DF, Buhner WA: Expanding habitat of the imported fire ant: a public health concern. J Allergy Clin Immunol 2000; 105: 683-691.

12. Caldwell ST, Schuman SH, Simpson WM: Fire ants: a continuing community health threat in South Carolina. J SC Med Assoc 1999; 95: 231-235.

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