A dynamic relationship between two regional causes of IgE-mediated anaphylaxis: α-Gal syndrome and imported fire ant

Background: A syndrome of mammalian meat allergy relating to IgE specific for galactose-alpha-1,3-galactose (alpha-Gal) was first reported 10 years ago in the southeastern United States and has been related to bites of the lone star tick (Amblyomma americanum). Objective: Here we investigated the epidemiology of the "alpha-Gal syndrome'' in the United States and sought additional evidence for the connection to tick bites. Methods: A survey of allergists was conducted by using a snowball approach. A second tier of the survey included questions about anaphylaxis to imported fire ants (IFAs). History of tick bites and tick-related febrile illness were assessed as part of a case-control study in Virginia. Antibody assays were conducted on sera from subjects reporting allergic reactions to mammalian meat or IFA. Results: In North America the alpha-Gal syndrome is recognized across the Southeast, Midwest, and Atlantic Coast, with many providers in this area managing more than 100 patients each. The distribution of cases generally conformed to the reported range of A americanum, although within this range there was an inverse relationship between alpha-Gal cases and cases of IFA anaphylaxis that were closely related to the territory of IFA. The connection between tick bites and alpha-Gal sensitization was further supported by patients' responses to a questionnaire and the results of serologic tests. Conclusions: The alpha-Gal syndrome is commonly acquired in adulthood as a consequence of tick bites and has a regional distribution that largely conforms to the territory of the lone star tick. The epidemiology of the syndrome is expected to be dynamic and shifting north because of climate change and ecologic competition from IFA.