Prevalence of type I sensitization to alpha-gal in forest service employees and hunters

Background: The production of IgE molecules specific to the carbohydrate galactose-α-1,3-galactose (alpha-gal) is known to induce delayed anaphylaxis against mammalian meat. Tick bites constitute the primary sensitization source, as ticks transfer alpha-gal in their saliva to a host during a bite. The reported prevalence of alpha-gal-specific IgE (alpha-gal-sIgE) positivity varies between different populations from diverse geographic regions. Objective: To investigate the prevalence of alpha-gal-sIgE positivity in a population of forest service employees who are highly exposed to ticks in comparison with a residential population and a historic sample. Methods: A cross-sectional study evaluating 300 forest service employees and hunters from southwest Germany was performed. Alpha-gal-sIgE levels were assessed by ImmunoCAP assay. The prevalence of alpha-gal-sIgE-positive individuals was compared with a matched cohort composed of a residential population and blood samples from forest service employees collected 15 years ago. Results: In the study population, the prevalence of alpha-gal-sIgE-positive (≥0.10 kU_A/L) individuals was 35.0%, whereas the prevalence of individuals with alpha-gal-sIgE levels ≥0.35 kU_A/L was 19.3%. Alpha-gal-sIgE positivity was associated with total IgE levels and recent tick bites. Mammalian meat-induced delayed anaphylaxis was found in 8.6% of the participants with alpha-gal-sIgE levels ≥0.35 kU_A/L. For forest service employees and hunters, the odds ratio for alpha-gal-sIgE positivity was 2.48 compared to the residential population. The prevalence of alpha-gal-sIgE positivity in the current and historic cohort was comparable. Conclusion: Forest service employees and hunters compose a population with a high prevalence of alpha-gal-sIgE positivity and carry a considerable risk of red meat allergy.