Systemic reaction rates to field stings among imported fire ant-sensitive patients receiving >3 years of immunotherapy versus <3 years of immunotherapy

As imported fire ants (IFAs) expand their range, hypersensitivity reactions to their stings are becoming a significant cause of morbidity and mortality in the United States. Currently, IFAs whole body extract (WBE) immunotherapy is the mainstay of treatment for IFA hypersensitivity but the optimal duration of treatment is unknown. A questionnaire was administered to patients diagnosed with IFA venom hypersensitivity based on history and the presence of IFA venom-specific IgE who had been offered immunotherapy. The patients were grouped into those who received <3 years of immunotherapy and those who received <3 years of immunotherapy. Forty of the 272 patients initially identified were successfully contacted (14%) with 6 patients being excluded. Of these patients, 19 reported having received <3 years of IFA immunotherapy (reduced course) and 15 stated they had been given >3 years of immunotherapy (complete course). Subsequent field stings were reported by 18 (95%) of the reduced course groups and 14 (93%) of the complete course group with 1 person from each group (6 and 7%, respectively) experiencing a systemic reaction. There were no significant differences between the two groups in the number of patients with subsequent field stings or systemic reactions after subsequent IFA stings. Less than 3 years of IFA immunotherapy may offer long-term protection against IFA hypersensitivity reactions although additional studies with more subjects and controls are necessary before definitive conclusions may be made.