<b>α</b>-Gal IgE Prevalence Patterns in the United States: An Investigation of 3000 Military Recruits

The alpha-gal syndrome is a mammalian meat allergy caused by IgE to galactose-alpha-1,3-galactose (alpha-gal). Tick bites from Amblyomma americanum (the lone star tick) are strongly associated with alpha gal syndrome in the United States. This investigation of military recruits sought to investigate alpha-gal IgE prevalence, regional patterns, and risk factors.Using banked serum from the Department of Defense Serum Repository, the present study is based on samples obtained from service members whose initial assignment was at a military base within the geographic range of A. americanum between 2001 and 2007, to include installations in Arkansas, Kentucky, Missouri, North Carolina, Rhode Island, South Carolina, and Virginia. Among a cohort of 3000 subjects, 2456 (81.9%) were male, with a median age of 19 years. Homes of record for the service members spanned 50 states, with a median of 36 service members per state.Alpha-gal and total serum IgE were measured by ImmunoCAP. Alpha-gal IgE was considered positive at greater than or equal to 0.1 International Units, and was related to home of record at enlistment, as defined by a 3-digit zip code based on 2000 US Census Bureau Zip Code Tabulation Area boundaries. Granular mapping of alpha-gal sensitization was compared with tick distribution and Ehrlichia chaffeensis infection cases using Centers for Disease Control data.The prevalence of alpha-gal IgE among incoming military personnel was 6%. The highest prevalence rates were in service members with homes of record in Arkansas (39%), Oklahoma (35%), and Missouri (29%). Total IgE was higher among sensitized versus nonsensitized service members. Among positive alpha-gal IgEs, the geometric mean was 0.53 IU/mL.The presence of alpha-gal IgE closely correlated with county-level A. americanum reports and E. chaffeensis infections. However, clusters were apparent in the prevalence map that did not match with either A. americanum or E. chaffeensis. This suggests the possibility that other tick species may lead to alpha-gal sensitization in the United States, as is known to occur outside of the United States. Alpha-gal sensitization was associated with male gender, rural residence, and white race in univariate and multivariate models.The present study presents data from a unique patient cohort. The authors note that military recruits may have had multiple residences before entering military service. In Virginia, North Carolina, and Kentucky, alpha-gal IgE prevalence rates were lower than previously reported. The authors note that regional variance within states is apparent on granular clustered mapping that correlates closely with established A. americanum presence. The present study provides an opportunity for targeted education within known risk areas. Additional study is needed to explore potential exposures in regions that are not well-explained with A. americanum presence.