Red Meat Allergy From Ticks: Reality or Science Fiction?

Apparently, people love their red meat. Either that, or they find news of a rare allergy that can result from a tick bite juicy fodder for water-cooler chit-chat.

Since a recent Centers for Disease Control and Prevention (CDC) report that alpha-gal (galactose-α-1,3-galactose) syndrome developed from a tick bite might be less of a medical rarity than previously thought, news of the odd allergic reaction to red meat has gained public attention, particularly among steak lovers.

See related story on how to avoid tick bites.

Nearly half a million Americans have the allergy, with many more likely undiagnosed, according to the CDC. With the state in the midst of a high tick season, CU Anschutz Today asked two tick experts with the University of Colorado Anschutz Medical Campus about the alpha-gal allergy and the risk.

Here’s what Daniel Salkeld, an instructor with the Colorado School of Public Health, and Daniel Pastula, MD, associate professor at the CU School of Medicine Department of Neurology and the ColoradoSPH, had to say.

What is this alpha-gal allergy and how do people get it from ticks?

Pastula: We don’t have all the details, but our best theory right now based on the current knowledge is the lone star tick can carry the alpha-gal sugar in its saliva. It’s a sugar molecule that is not present in humans. So basically when the tick bites, we think you get exposed to this sugar and have an immune response to that sugar that results in this allergic reaction. Some people – and not everyone develops the reaction – can then mount a response to meat where the sugar is found (often hours after eating).

Salkeld: It's not an infectious disease, i.e., a pathogen vectored by ticks between hosts like Lyme disease or Colorado tick fever. Rather, it's an allergy prompted by the bite of a lone star tick. People sometimes develop this serious allergy to 'alpha-gal,' a sugar molecule found in most mammals. They then can experience a range of symptoms after exposure to the alpha-gal in pork, beef, rabbit, lamb, venison, etc., and even some meat derivatives, such as gelatin or dairy products. Symptoms can include nausea, diarrhea, dizziness, difficulty breathing and anaphylactic shock – which can be fatal.

Do these lone star ticks exist in Colorado?

Salkeld: These are not an established species in Colorado, but the distribution range is evolving and changing (hence increased awareness of alpha-gal as new populations become at risk). Lone star ticks (identifiable by a single, white, star-like mark) have been sporadically found in Colorado, but so far are isolated incidents.

Potentially, other tick species may induce alpha-gal syndrome, but that remains unknown.

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How would you describe the risk in Colorado?

Pastula: Very low. But it’s important to be aware of other tick-borne diseases (e.g., Colorado tick fever, etc.) that do occur in Colorado. Ticks are bad news, and we need to be doing everything we can to avoid tick bites.

Salkeld: Given the rare nature of lone star ticks in Colorado, the risk is that you get bitten when traveling (see map). They are also considered an aggressive tick – actively searching out a blood meal instead of waiting on vegetation for a potential host to walk by. (Map Source: Centers for Disease Control and Prevention)

Why do you think this particular tick fact is grabbing so much public attention?

Salkeld: A person who found a lone star tick in Wheat Ridge stated that he was more afraid of alpha-gal syndrome and its impacts on his barbecuing and diet than he was of Lyme disease. The impacts of tick bites and tick-borne diseases vary – ranging from annoying to debilitating to deadly. But the notion of an allergy to meat, and for this to happen at any age, with such potentially disturbing consequences (anaphylactic shock) does seem like the invention of a disturbed science-fiction writer.