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Spring and summer 2017 saw a rash of media reports warning of the spread of a rare tick whose bite, in addition to causing skin irritation, stomach cramping, breathing problems, and other familiar tick-related symptoms in human beings, purportedly triggers an allergic reaction to red meat. Meet the N.J. Tick that Can Turn You into a Vegetarian, joked the headline of a story published on NJ.com in mid-May: Among the dozens of similar stories published around the same time, the Williamsburg Yorktown Daily reported that tick-borne meat allergies were on the rise in Hampton Roads, Virginia, Minnesota Public Radio noted that a rare, tick-triggered meat allergy is becoming more common in northern Minnesota, and a 17 June 2017 post on popular science blog IFLScience warned that a tick responsible for causing meat allergies is currently spreading around America: Apart from the attention-grabbing phrase reverse zombie, which is new in this context, the 2017 reports echoed a spate of stories published three years earlier reporting on the same phenomenon. Common to all of them are the claims that the lone star tick is believed responsible for causing a red meat allergy and that the tick's habitat is expanding. Although they were undeniably sensationalized, the claims are true. Scientists have been aware for some time that the lone star tick (Amblyomma americanum), first discovered in 1754, transmits pathogens associated with three rare but potentially fatal infections (Ehrlichia chaffeensis, Ehrlichia ewingii, and Borrelia lonestari), though it wasn't until the late 2000s that its connection to mammalian meat allergy (MMA for short, and also known as alpha-gal allergy), was established. A link between tick bites and MMA was first proposed by Australian researchers who discovered that 24 of the 25 people they were monitoring for a study on meat allergies reported that they had been bitten by ticks (in Australia, the culprit was identified as the Australian paralysis tick). At around the same time, U.S. researchers identified a specific allergen that triggered red meat reactions, a carbohydrate found in mammalian cell membranes called galactose-alpha-1,3-galactose (alpha-gal). Despite being aware that the geographical ranges of reported meat allergies and occurrences of the tick-borne illness Rocky Mountain spotted fever roughly coincided, it wasn't until the U.S. researchers shared a moment of pain-inspired serendipity that they narrowed down the cause: In plain English, it turned out that all three researchers had been bitten by ticks, developed red meat allergies, and experienced a dramatic increase in blood serum levels of alpha-gal antibodies, suggesting that the tick bites had triggered their sensitivity to the carbohydrate. Further research confirmed their suspicions, though questions remain about the precise mechanism by which a tick bite triggers the alpha-gal autoimmune response. (The fascinating story of the chain of events leading to the discovery is told by the researchers themselves in The Alpha-Gal Story: Lessons Learned from Connecting the Dots in The Journal of Allergy and Clinical Immunology [March 2015], and also to entertaining effect in a March 2014 article by New Yorker writer Peter Andrey Smith.) With regard to its geographical distribution, the Centers for Disease Control confirms that the lone star tick population has been on the increase for the past few decades: These two CDC maps shared with us by allergy researcher Dr. Scott Commins shows how the distribution of the lone star tick in the U.S. changed between 2010 and 2012: According to the American College of Allergy, Asthma, and Immunology, an allergic reaction to red meat (regardless of the specific trigger) can result in symptoms ranging from a mild case of hives to life-threatening anaphylaxis. The good news is that those afflicted by the MMA response can still either eat only poultry and fish or mitigate their symptoms somewhat by taking antihistamines before consuming red meat, and the allergy may recede over time; however, the immune response is generally thought to linger for life. Although the incidence of tick-induced meat allergies remains comparatively uncommon to date, experts say, they also remind the public at large that tick bites can transmit any number of serious diseases, so a familiarity with basic tick avoidance strategies is recommended.
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