In a recent Dispatch published in the journal Emerging Infectious Diseases, researchers from the U.S. Centers for Disease Control and Prevention (CDC), the Maine Center for Disease Control and Prevention (Maine CDC), the University of North Carolina, and other institutions reviewed a case study from Maine, identifying Ixodes scapularis as a potential carrier of alpha-gal syndrome (AGS). The research evaluated positive α-gal–specific IgE test results and case records spanning 10 years (2014–2023) as part of enhanced surveillance. They discovered that at least 23 Maine residents had contracted AGS from unknown or potentially non-lone star tick exposures, underscoring the need for improved surveillance and medical attention to bites from tick species beyond the lone star tick.
Background
Alpha-gal syndrome, colloquially referred to as the “mammalian meat allergy” or the “tick bite meat allergy,” is a severe allergic reaction to the disaccharide galactose-α-1,3-galactose (α-gal), commonly found in mammalian meat products.
The symptoms of AGS can range from rash, hives, nausea, difficulty breathing, and a drop in blood pressure, to severe stomach pain and, in rare cases, anaphylaxis. Traditionally, AGS has been associated with bites from the lone star tick (Amblyomma americanum), which is commonly found in the U.S. However, other tick species, such as Ixodes holocyclus in Australia, have also been implicated, suggesting that bites from Ixodes scapularis and Haemaphysalis longicornis may also trigger AGS.
Study Overview
This study investigates the case of a 45-year-old woman who exhibited AGS-like symptoms after being bitten by a non-lone star tick. The tick, identified as an adult female Ixodes scapularis, was confirmed by the CDC. The patient, who had no prior history of allergies, developed symptoms shortly after consuming roasted rabbit, including gastrointestinal (GI) distress such as abdominal pain and malaise. These symptoms recurred whenever she consumed mammalian meat, leading to further medical evaluation.
Following a range of medical tests, including a serum α-gal–specific IgE test, the patient’s α-gal IgE levels were found to be unusually high, confirming an allergic reaction to mammalian meat. Although she did not exhibit anaphylaxis, the symptoms were consistent with the gastrointestinal form of AGS.
Further follow-ups indicated that her α-gal IgE levels decreased over time, and eventually, she was able to tolerate red meat once more. However, the study highlights the persistence of symptoms and the need for careful monitoring of tick-borne AGS cases.
Study Findings and Follow-Up
The study findings suggest that Ixodes scapularis ticks may trigger hypersensitivity reactions and AGS in humans. This prompted the CDC and Maine CDC to retrospectively review patient records from Maine, identifying 57 individuals who reported AGS-like symptoms. Out of these, 23 were found to have positive α-gal IgE test results.
Further interviews with confirmed AGS cases revealed exposure to various tick species, including lone star ticks, black-legged ticks, and others. This expanded the potential geographical reach of AGS, indicating that the condition may be more widespread than previously thought.
Conclusion
This study presents strong evidence that non-lone star ticks, particularly the black-legged tick (Ixodes scapularis), can trigger AGS in humans, greatly expanding the known distribution of the syndrome. In response, the CDC has increased surveillance efforts and advised clinicians to routinely screen tick-bite patients for α-gal–specific IgEs to detect and manage AGS more effectively. This underscores the importance of heightened awareness among healthcare professionals regarding tick-borne allergies and their potential link to red meat hypersensitivity.
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