How Itchy Feet Led A Researcher To The Tick-Born Cause Of A Meat Allergy
One Saturday afternoon at a backyard cookout, St. Louis, Missouri, architect Dan Rosenberg enjoyed a cheeseburger – a food he’d enjoyed many times before.
That night, a couple hours after he went to sleep, he woke up with a searing pain in his stomach—pain he describes as “a nine on the ten-scale.”
After the same thing happened a few more times, Rosenberg went to his doctor and underwent about a month of blood tests. The tests were inconclusive but after Rosenberg brought in a record of his diet—he’d eaten meat before each episode -- his doctor told him about a rare red meat allergy that could be brought on by tick bites.
When he heard that, Rosenberg says he got a sinking feeling: “I remembered exactly two weeks before the first reaction, I had gotten a tick bite.”
Becoming allergic to red meat is a rare reaction some people can have to the bite of the Lone Star tick. It may be becoming more common. Recent research has shown that global warming is causing most types of ticks, including the lone star, to expand their range. Distinctive for the white dot on its back, the Lone Star tick is already found commonly throughout the South and Midwest and as far north as Maine.
Researchers didn’t understand the connection between the parasite and this unusual allergy until a few years ago. Dr. Thomas Platts-Mills, head of the Asthma and Allergic Disease Center at the University of Virginia, worked out the connection, thanks in part to a coincidence. He himself had a reaction to a tick bite while doing unrelated research on a cancer drug.
He and his research team had been looking into what was causing some cancer patients to have sometimes severe reactions to the drug cetuximab.
Platts-Mills’s team isolated the reaction to a sugar in the drug called galactose-alpha-1, 3-galactose, known simply as alpha-gal.
They made the connection to the red meat allergy because alpha-gal is also found in the meat of most non-primate mammals, including cows, pigs, lamb and deer. Platts-Mills says they were seeing patients who reported allergic reactions to those meats -- sometimes presenting as itching and hives, but at other times showing more severe symptoms of anaphylaxis.
But what was causing the patients to develop the allergy remained elusive, until they noticed an overlap between where the reactions were occurring and the range of the Lone Star tick. Platts-Mills’s itchy feet offered an opportunity to test that theory.
He says he took blood samples every week for the next six weeks after he was bitten and he could actually see his level of antibodies going up.
Those are special antibodies that are specific to alpha-gal and are responsible for an allergic reaction to the sugar. A bite from a Lone Star tick that’s already fed on an animal that carries alpha-gal can cause humans to develop the antibodies.
Platts-Mills published his preliminary findings in 2009 and the results of more extensive research in 2013. He continues to research the allergy.
Not everyone who is bitten by a Lone Star tick will develop the allergy, however, and Platts-Mills says the tick’s uniquely itchy bite provides a useful indicator.
“If a person reports tick bites and they itch for more than two weeks after the bite,” he says, “then they are likely to have the alpha-gal allergy.”
An intradermal allergy test, though, is more accurate.
In some cases the allergy can go away in a year or two, but for most who develop it, it’s permanent. And the only solution is to stop eating red meat. You can still eat fish, chicken and turkey, though. For Platts-Mills this wasn’t such a bad thing:
“I was over 50 at the time and my cardiologist was already telling me not to eat red meat.”
Bram Sable-Smith is a reporter based in Columbia, MO. Reach him at firstname.lastname@example.org and follow him on Twitter at @besables.