Tick bites can trigger a severe, delayed allergic reaction to red meat, suggest findings published in the Journal of General Internal Medicine.
The syndrome is specific to lone star ticks and occurs due to development of immunoglobulin E antibodies to a carbohydrate known as galactose-α-1,3-galactose (alpha-gal) in response to a bite from these arachnids. As alpha-gal is present in red mammalian meat such as steak, it then results in an allergic reaction triggered on consumption.
Susan Wolver (Virginia Commonwealth University, Richmond, USA) and colleagues report three cases of this phenomenon and describe the syndrome further.
They note that the newly reported reaction is unusual in that it is in response to a carbohydrate rather than a protein and occurs 3-6 hours after consumption, whereas most anaphylactic reactions occur immediately after consumption. The researchers believe the delay may be due to the specific biochemistry, digestion, and absorption of alpha-gal by the body.
The three cases reported by Wolver and team include those of two men aged 82 and 54 years and that of a 29-year-old woman. The 82-year-old man and the woman reported prior tick bites and the 54-year-old man a history of anaphylaxis in response to insect stings.
All three experienced severe allergic reactions during the night on at least one occasion, involving development of hives and anaphylaxis, after eating red meat between 3 and 6 hours earlier.
When tested for alpha-gal antibodies all the patients had levels significantly above the normal range.
After being advised to avoid red meat, the men and woman have remained symptom free to date.
"Where ticks are endemic, for example in the southeastern United States, clinicians should be aware of this new syndrome when presented with a case of anaphylaxis," suggest the authors.
"Current guidance is to counsel patients to avoid all mammalian meat - beef, pork, lamb and venison."
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