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Researchers Tie Tick Bites to Serious Red Meat Allergy


July 27, 2012 — A bite from the lone star tick can cause a person to develop a delayed, life-threatening allergic reaction to eating beef or other mammalian meat, according to an article published online July 20 in the Journal of General Internal Medicine.
Susan E. Wolver, MD, from the Department of General Internal Medicine at Virginia Commonwealth University, Richmond, and colleagues advise that clinicians be aware of the new syndrome, which can produce pruritic hives and other symptoms 3 to 6 hours after eating, rather than the usual 1 hour. The syndrome has been confined, at least initially, to the southeastern United States, where the lone star tick is endemic. The tick bite is thought to produce immunoglobulin E (IgE) antibodies to the carbohydrate galactose-alpha-1.3-galactose (alpha-gal), a carbohydrate moiety in mammalian meat glycoproteins or glycolipids.
In their description of the new syndrome, the researchers analyzed case studies of 3 patients, 2 of whom had to visit emergency departments for care after eating beef and 1 who experienced the reaction while at work in an emergency department. Their treatments included combinations of diphenhydramine, epinephrine, steroids, albuterol, and/or intravenous fluid.
The first patient, an 82-year-old man, ate beef tenderloin for dinner at 6 pm and woke up around 11 pm with pruritic hives and the urge to urinate. He self-administered diphenhydramine but collapsed, losing consciousness en route to the bathroom. His wife, who had removed a tick from his back a few days earlier, called 911. "The allergy/immunology workup revealed IgE alpha gal >100 kU/L (Viracor-IBT, reference range <0.35 kU/L), specific IgE to beef 45 kU/L and to pork 53 kU/L (ImmunoCAP, Phadia, reference range <0.35 kU/L)," the authors write.
The second patient, a 54-year-old man, had prime rib for dinner and awoke about 2 am with hives on his thighs that progressed to generalized hives along with swelling of his lips and tongue despite self-administered diphenhydramine. With his second dose of diphenhydramine he became dizzy and felt his throat closing; he gave himself an epinephrine injection (which he had because of a history of anaphylaxis to insect stings) and called 911. His subsequent skin prick test was negative to beef and pork. However, "[h]is IgE alpha-gal was 3.94 IU/mL (University of Virginia, reference range <0.35 IU/mL), specific IgE to beef 1.5 kU/L and to pork 0.7 kU/L," the authors write.
The third patient, a 29-year-old woman who recalled being bitten by ticks years ago and had a history of allergic reactions, developed abdominal cramps and pruritic hives on her arms about 5 hours after eating a cheeseburger. Her coworkers warned her that her face and upper chest turned "beet red." "Laboratory tests showed IgE alpha-gal was 10.40 kU/L, and specific IgE to beef and pork were 5.50 kU/L and 5.10 kU/L, respectively," the authors write.
All 3 patients have abstained from beef, pork, and/or lamb since their episodes and have remained free of allergic symptoms. The authors note tolerance to chicken, turkey, and fish for these patients.
Cetuximab and Red Meat Share the Alpha-Gal Carbohydrate Moiety
Previous research has shown an association between anaphylaxis and treatment of patients with the cancer drug cetuximab, a chimeric mouse-human monoclonal antibody that contains alpha-gal. Those patients developed allergic symptoms within minutes of receiving cetuximab. However, the geographic distribution of the patients matched the geographic distribution of the lone star tick (Amblyomma americanum) in the southeast.
"Alpha-gal is unique, as it is a carbohydrate recognized by IgE antibodies," the current researchers write.
"The alpha-gal story is truly a paradigm-shifting phenomenon for three distinct reasons. First, anaphylaxis occurred with the primary exposure to the glycoprotein cetuximab. Second, with regard to meat ingestion, anaphylaxis is delayed several hours rather than immediate. And third, meat-induced anaphylaxis is the first food-induced anaphylaxis due to a carbohydrate rather than a protein," the authors conclude. "Avoidance of all mammalian meat (including beef, pork, lamb, and venison) is the current recommendation for alpha-gal sensitized patients."
The authors have disclosed no relevant financial relationships.

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