Many children stung by fire ants in southeast U.S.

NEW YORK (Reuters Health) - A new study suggests that many children in the southeastern United States are stung by fire ants, as evidenced by signs of an immune system reaction to the fire ant venom. Although this can put them at risk for a potentially severe allergic reaction the next time they are stung, the prevalence of severe reactions in this group is very low.

Therefore, Dr. Megan E. Partridge of the Medical College of Georgia in Augusta and colleagues suggest that physicians practicing in this area need to be careful when interpreting antibody test results in children who don't have a history of severe allergic reaction, also referred to as anaphylaxis, following a fire ant sting.

Red imported fire ants infest much of the southeastern U.S., and up to 60 percent of people living in infested areas are stung each year. The ants build mounds in the dirt that can reach more than a foot in height, and they are aggressive about defending their home.

Because children often play outside, they are especially likely to be stung by the insects.

Past research has found that many adults who have been stung by a fire ant are subsequently sensitized to the venom -- meaning they have immune system antibodies directed at the venom. This increases their risk of having a potentially serious allergic reaction the next time they are stung.

For the new study, researchers tested blood samples from 183 children and teenagers for antibodies to fire ant venom. They found that antibodies were evident in some children even before their first birthday. Among 11- to 20- year-olds, more than 97 percent had antibodies to fire ant venom.

This high prevalence of sensitization far surpasses what has been found among adults in the Augusta area, according to Partridge's group.

However, few of the children -- about 2 percent -- had ever had a severe allergic reaction to a fire ant sting, she and her colleagues report in the Annals of Allergy, Asthma & Immunology.

They say more research is needed to understand why, despite the widespread sensitization, so few children had serious allergic reactions.

The fact that nearly all of the older children had antibodies to fire ant venom likely reflects their having been stung multiple times, according to Partridge's team.

Repeated exposure to the venom increases the chances of developing an allergy. However, frequent exposure to the toxin may also cause desensitization to occur.

Experts recommend that children living in ant-infested areas always wear socks and shoes outdoors. Families with fire ant mounds in their yard can use insecticides to try to get rid of the pests.

Research has suggested that topical insect repellants are not a good fire ant defense.

SOURCE: Annals of Allergy, Asthma & Immunology, January 2008.