A few years ago, doctors in the southern United States started noticing an odd phenomenon: people were becoming allergic to red meat, seemingly out of the blue. What in the environment was causing this response? The answer, surprisingly, turned out to be ticks.
The researchers who figured this out came upon the explanation serendipitously. Thomas Platts-Mills and his colleagues had been studying a cancer drug called Erbitux that was causing severe allergic reactions in patients – but only in southern states. The team had concluded that these people were carrying an antibody that responded to sugars in the drug.
In their findings – published in 2008 – the researchers noted that the sugars in Erbitux, which is derived from mouse cells, are also present in beef, pork and cow milk.
So the following year when it came to light that otherwise healthy people were developing meat allergies – also in the South – the team began testing samples of their blood and found that they possessed the same Immunoglobulin E (IgE) antibodies as the cancer patients who had reacted to Erbitux.
Since people were reporting a 3-5 hour delay between ingesting meat and having a reaction, scientists guessed that the sugars triggering the response were stored in the fat of the animal, which takes longer to digest than protein or carbohydrates. That would explain why the reaction wasn’t immediate like most other food allergies.
But the big mystery remained: Where were these antibodies for alpha-gal (the sugars found in Erbitux and red meat) coming from?
“We thought initially that it was a parasite,” says Dr. Scott Commins, an assistant professor of medicine at UVA working on the project under Platts-Mills. “So we screened for all kinds of crazy parasites.”
Then, in August of 2009, the answer quite literally came to Platts-Mills when his own IgE to alpha-gal levels suddenly spiked days after he was bitten repeatedly by ticks while on a hike in the woods.
Out of curiosity, the researchers began asking patients if they had been bitten by ticks before their meat allergy developed.
“Once we opened up that line of questioning, it just blew up on us,” Commins told Food Safety News.
Of the over 1,500 people who have now reported meat allergies to the researchers, at least 90 percent say they were bitten by ticks in the weeks preceding their allergic reaction, he says.
While cases are mostly concentrated in the South in Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee, Texas and Virginia, allergy clusters have also cropped up in Pennsylvania and the East Hamptons in New York, says Commins.
The challenge the team faces now is figuring out why this tick – called the “lone star tick” because of a small white mark on its back – is producing an immune response to alpha-gal in humans.
“That’s what we have left to do,” says Commins. “What is it about the tick? Is it a new organism in the tick saliva that is inducing this response?”
Or is it something these ticks have always carried, but meat allergies are only being detected now because there are more of these ticks out there?
These are both theories being considered, he says.
In the meantime, more cases continue to flood in.
“Today alone I’m looking at 25 emails from people across the country and yesterday there were in order of 50,” Commins reported during Friday’s interview.
After just 15 minutes of talking with Food Safety News, Commins received 2 more e-mails. One man reported developing a beef allergy 5 years ago, and said he doesn’t react well to tick bites and they take a long time to heal.
“We hear that all the time,” says Commins. A lingering bite is one of the signs that a person may have been bitten by an allergy-causing tick, he explains.
The bite also becomes itchy and a hard knot forms under that part of the skin.
So for those wondering if they may have an allergy-causing bite from a lone star tick, “I tend to say if the bite hangs around for 2-3 weeks and it’s itchy then I would get tested.
Is there anything you can do once you’ve been bitten to avoid developing a meat allergy?
Unfortunately, says Commins, the answer is no. “My sense is the bite itself is enough to cause the allergy to happen. They don’t have to be attached for very long at all.”
The good news for those who develop the allergy is that it seems to go away in 3-5 years, says Commins. The bad news is if you’re bitten again, the allergy could be more severe and long-lasting.
The government has not yet issued any health warnings about meat allergies associated with the lone star tick. The Centers for Disease Control and Prevention’s lone star tick information page lists only southern tick-associated rash illness (STARI) as a potential health consequence.
© Food Safety News