Incidence of Alpha-Gal IgE Sensitization in 3000 Military Personnel, Assessing Sex, Race, Installation, and Occupational Impacts

<b>Background/Objectives</b>: IgE to galactose-alpha-1,3-galactose (alpha-gal) is associated with <i>Amblyomma americanum</i> (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. <b>Methods</b>: 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 <i>A. americanum</i> 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. <b>Results</b>: 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. <b>Conclusions</b>: This study demonstrates that alpha-gal IgE seroconversion is occurring within the <i>A. americanum</i> 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.