Prevalence of allergic sensitization to imported fire ants in children living in an endemic region of the southeastern United States

Background: Imported fire ant (IFA) stings are common in children in the southeastern United States, but little is known about antibody responses to stings. Objectives: To examine the prevalence of detectable IgE and IgG antibodies to IFA venom (IFAV) and to assess the frequency of IFA stings in children in an endemic region. Methods: We measured IFAV specific IgE using the ImmunoCAP assay and IgG anti-IFAV using protein G solid-phase radioimmunoassay in 183 serum samples from children living in the southeastern United States. A questionnaire was used to collect information about insect stings and bites from 182 children in a general pediatric clinic. Results: Serum IgE anti-IFAV was detected (0.1 kUa/L) in 7.1% of 0- to 1-year-olds, 57.1% of 2- to 5-year-olds, and 64.4% of 6- to 10-year-olds. The prevalence of IgG anti-IFAV antibodies increased from 11.9% in 0- to 1-year-olds to 97.5% in 11-to 20-year-olds. Of children in the pediatric clinic, almost 40% had been stung by an IFA in the past month, with 23.9% receiving more than 6 stings per month. Conclusions: In endemic areas, the onset of sensitization (IgE positivity) to IFAV occurs in the first years of life, with more than half of the children demonstrating sensitization by 2 to 5 years of age. Exposure to IFAV as evidenced by a positive IgG anti-IFAV antibody increased with age, and by the second decade, more than 97% of children had detectable antibody. Children living in an endemic region frequently encounter IFAs and, when stung, often receive multiple stings.