Prevalence of alpha-gal allergy in Central Virginia
Published online June 27, 2024
IgE sensitization to galactose-alpha-1,3-galactose (alpha-gal) is strongly linked with bites from lone star ticks and is an important cause of mammalian meat allergy, often referred to as the alpha-gal syndrome (AGS). Owing to the connection with tick bites, the syndrome varies by region but is known to be common in the southeastern United States. Studies detailing AGS to date leave open several questions regarding prevalence, risk factors, and presentation.
The recent publication by Richards and Ailsworth, et al. in The Journal of Allergy and Clinical Immunology: In Practice investigated AGS using two cohorts studied at the University of Virginia (UVA). The cohorts were recruited as part of COVID-19 research but provided a unique opportunity to assess AGS prevalence in central Virginia. The first cohort recruited adults, mostly healthcare workers, receiving COVID-19 vaccines at the University. The second cohort involved patients evaluated in a post-COVID-19 follow-up clinic. There was no inclusion or exclusion criteria related to pre-existing comorbidities, including allergic conditions. Blood samples were available for all subjects and questionnaire information about medical history, diet, post-prandial symptoms and tick bite history was available in the vaccine cohort. IgE antibodies were measured to a panel of common allergens, including alpha-gal, with ImmunoCAP.
In the COVID-19 vaccine cohort, 16% (43 of 267 subjects) were sensitized to alpha-gal using a cut-off of 0.1 IU/mL. Of the 43 subjects who were sensitized, 7 reported symptoms consistent with mammalian meat allergy, equating to an overall AGS prevalence of 2.6%. In the COVID-19 patient cohort, detailed symptom questionnaires were not available, but 14% (18 of 125 subjects) were sensitized to alpha-gal. Combining the 392 individuals studied in the two cohorts equated to a local sensitization prevalence of 15.6% (95% CI, 12.3-20). Alpha-gal sensitization was not associated with GI symptoms or diagnoses; however, there was a significant association with frequent antacid use. Tick bite history, higher total IgE, and older age were also associated with alpha-gal sensitization. Among those who were sensitized, alpha-gal IgE levels were higher among those reporting mammalian meat allergy than those not reporting meat allergy (9.0 IU/mL vs 0.5 IU/mL, P<0.001). These results suggest that in central Virginia, and likely other parts of the country where lone star ticks are established, AGS should be appreciated as a major cause of adult food allergy. Providers should be aware of AGS and consider alpha-gal IgE testing in patients with relevant clinical history, while understanding that many members of the community may be sensitized but apparently could tolerate meat or dairy without overt allergic reactions.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.
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