Lots of Americans have had the potential joy of eating a juicy steak taken away from them by a measly tick, new research out this week has found. The study estimates that up to 450,000 people in the U.S. have developed alpha-gal syndrome since 2010, otherwise known as an allergy to red meat. The condition is caused by the bite of certain ticks, and new cases seem to be increasing over time.
Alpha-gal is a sugar found in the muscles of most mammals, with humans being an important exception. Our natural lack of alpha-gal is one major reason why we can’t use transplanted organs from nonhuman animals like pigs, since our bodies can develop a severe immune response to its constant presence (recent advances in this field have only become possible because of gene-editing technology that can produce pigs born without alpha-gal).
People can normally tolerate the alpha-gal found in the meats and other food products we eat without issue. But, for reasons we’re still trying to understand, the bite of a lone star tick (Amblyomma americanum) and other species can sometimes cause our bodies to develop a new overzealous immune response to the sugar, and by extension, to red meat and even dairy. This response is similar to a typical food allergy, meaning that it triggers symptoms through the production of immunoglobulin E antibodies. But it’s the only known food allergy to a carbohydrate, rather than a protein. Symptoms also tend to appear hours after exposure, rather than the minutes it takes for other foods.
Scientists first discovered that ticks can cause alpha-gal syndrome about two decades ago. But there’s still so much we don’t know about the condition, including how many people might actually have it. In this new research, a team of scientists from the Center for Disease Control and Prevention as well as other alpha-gal experts have tried to figure out that question in particular.
To come up with their estimates, they first looked at alpha-gal antibody testing data collected in the U.S. from 2017 to 2022. Notably, the data comes from a single commercial lab that was almost the only place where this testing was available in the U.S. until recently.
During the study period, 357,119 tests were collected, accounting for over 290,000 people. Of these, about 90,000 people tested positive for the allergy. Coupled with studies that collected earlier testing data, the team identified 110,229 suspected cases of alpha-gal syndrome that were documented during 2010–2022.
It’s possible that some of these positive results might not indicate a genuine case of the syndrome. But it’s also possible that many people who develop the allergy might have not visited a doctor knowledgeable enough to seek testing for it, or might have never sought medical attention at all. The authors estimate that anywhere from 96,000 to 450,000 people in the U.S. have contracted a red meat allergy from ticks since 2010, though there’s reason to believe that the true number is on the higher end. In a separate study by the same authors, also published this week by the CDC, they found that 42% of surveyed medical professionals weren’t even aware that the condition existed.
“If the projection and estimate of nearly 450,000 cases is even approximately correct, this is the number 10 allergy in the country behind sesame, which is number nine and affects roughly half a million people,” study author Scott Commins, the associate chief for allergy and immunology at the University of North Carolina School of Medicine, told CNN.
While more research will be needed to shore up these estimates, the overall picture isn’t looking good. The number of annual positive results for alpha-gal increased over time until 2022, though it’s likely this reported decrease only happened because more testing labs have now become available, the authors say. Other research has shown that the range of the lone star tick, mostly found in the Southern and Central U.S., is continuing to expand—thanks in no small part to factors like climate change—which then creates more opportunities for cases.
There is no treatment or cure for alpha-gal syndrome, though it can be managed through lifestyle changes and can sometimes spontaneously fade away over time.