A Meat Allergy Linked to Tick Bites May Be Increasing in the U.S., CDC Report Finds

A meat allergy associated with tick bites may affect close to half a million people in the United States, according to a new estimate from the Centers for Disease Control and Prevention.

Last week, the agency released two reports on alpha-gal syndrome (AGS), an allergy with symptoms that can be triggered by eating red meat or exposure to products made from mammals. The condition is most strongly tied to bites from lone star ticks.

In one of the studies, researchers looked at official results of tests for the allergy. They found that 90,018 U.S. residents tested positive for AGS between 2017 and 2022. And the number of people who tested positive increased—from 13,371 in 2017 to 18,885 in 2021. Including earlier cases revealed in a previous study, the CDC identified 110,229 suspected cases between 2010 and 2022.

The CDC estimates that since some people with AGS might not get tested, as many as 450,000 people may have the syndrome, according to a statement from the agency.

If the number of cases is truly that high, AGS would be the tenth most common food allergy in the country, Scott Commins, a co-author of both studies and an allergist at the University of North Carolina at Chapel Hill, tells Mike Stobbe of the Associated Press (AP).

A growing number of Americans are developing a meat allergy caused by tick bites. Here’s what we know about alpha-gal syndrome … pic.twitter.com/F5ApQU9gwL

— Brut America (@brutamerica) July 31, 2023

The second CDC study asked 1,500 health care providers about their knowledge of alpha-gal syndrome. The survey found that 42 percent of respondents were not aware of the allergy and that an additional 35 percent were not confident in their ability to diagnose or manage AGS patients. Only 5 percent felt very confident in their ability to do so.

As a result, the number of people who receive positive tests for AGS likely represents only a fraction of those with the condition, the studies suggest. As many as a few hundred thousand cases may go undiagnosed.

“This is a story that every patient of mine tells me, that ‘I had to go to five physicians before they could tell me what it was,’” Maya Jerath, an allergist and immunologist at Washington University in St. Louis who was not involved with the studies, tells the New York Times’ Emily Anthes. “It’s nice to have numbers behind it, and it’s definitely a call to action.”

People in the U.S. commonly get AGS when a lone star tick bites them, passing the sugar molecule alpha-gal through their skin, per Mayo Clinic. This can cause the body’s immune system to react to the sugar, which is present in most mammals, but not fish, reptiles, birds or humans, according to the CDC. The sugar can be found in meats including pork, beef, lamb and venison, as well as products made from mammals, including cow’s milk and milk products.

Symptoms of AGS include hives or rashes, nausea or vomiting, shortness of breath or difficulty breathing, and heartburn or indigestion. They can range from mild to severe or even life-threatening, per the CDC.

However, symptoms are typically delayed for two to six hours after consuming alpha-gal, and they may not occur after every exposure. AGS is “consistently inconsistent,” Johanna Salzer, a co-author of both studies and a disease ecologist at the CDC, tells the Times. “So this makes it a real challenge for health care providers.”

Lone star ticks are most commonly found in southeastern, south-central and mid-Atlantic states, but they’ve been spotted as far west as Colorado and Wyoming and as far north as Maine, according to the University of Rhode Island. The adults are active from April to late August. While AGS is primarily tied to lone star ticks, it might also be connected to other kinds of ticks, per the CDC.

The agency says that AGS is diagnosed through a patient history, physical exam and blood test from a health care provider and recommends preventing tick bites to reduce your chance of getting the syndrome.

“Alpha-gal syndrome is an important emerging public health problem, with potentially severe health impacts that can last a lifetime for some patients,” Ann Carpenter, a co-author of both studies and epidemiologist at the CDC, says in the statement. “It’s critical for clinicians to be aware of AGS so they can properly evaluate, diagnose and manage their patients and also educate them on tick-bite prevention to protect patients from developing this allergic condition.”

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.