Abstract
Background/Objectives: IgE to galactose-alpha-1,3-galactose (alpha-gal) is associated with Amblyomma americanum (lone star tick) bites, accounting for the regional distribution of the alpha-gal syndrome (AGS). Longitudinal studies describing risk factors for incident alpha-gal sensitization are lacking. The objective of this project was to assess the incidence of alpha-gal IgE seroconversion and identify associated demographic, occupational, and geographical risk factors among US military personnel. Methods: Samples from the Department of Defense Serum Repository were evaluated at two time points at least 3 years apart. In total, 3000 service members stationed at 10 military installations within the A. americanum tick range were included. Installation, sex, race and ethnicity, rank, military occupation, and branch of service were evaluated. Alpha-gal IgE seroconversion was defined as a change from <0.1 kU/L) to ≥0.1 kU/L. Results: Among the 2821 personnel who were alpha-gal IgE-negative at baseline, 138 (4.9%) seroconverted over a mean interval of 3.4 years. Seroconversion was more frequent in males (5.5% vs. 1.9%), White individuals (6.6% vs. 1.0% in Black people and 1.5% in Hispanics), and individuals in occupations with higher presumed outdoor exposure (e.g., infantry/law enforcement: 12.7% vs. administrative: 1.2%). Differences were not significant between sexes when accounting for military installation/occupation, but differences in race and ethnicity remained significant. Conclusions: This study demonstrates that alpha-gal IgE seroconversion is occurring within the A. americanum tick range and is associated with White race and ethnicity, and occupations with higher outdoor exposure. Further research is needed to elucidate the influence of race and ethnicity on alpha-gal sensitization and develop effective prevention and treatment strategies for AGS.