Red meat allergy caused by ticks is an 'emerging public health concern': CDC

A red meat allergy caused by tick bites is an "emerging public health concern," according to two new studies from the Centers for Disease Control and Prevention.

Alpha-gal syndrome (AGS) is a serious, potentially life-threatening allergic reaction that arises after people eat red meat or consume products with alpha-gal, a type of sugar found in most mammals, the CDC says.

The syndrome is typically caused by a bite from the lone star tick, which transfers alpha-gal into the victim's body which in turn triggers an immune system response.

The CDC says the number of AGS cases are underdiagnosed in the U.S. and -- despite the spread of the condition -- many clinicians aren't even aware it exists, let alone how to diagnose it.

Between 2010 and 2022, there were more than 110,000 cases of AGS identified, according to the CDC.

The agency estimates the actual number of cases may be as high as 450,000 but notes the syndrome is underdiagnosed due to factors including that diagnosis requires a test, some providers are not familiar with AGS and some people with symptoms don't get tested.

AGS symptoms can include hives or itchy rash, nausea or vomiting, heartburn or indigestion, diarrhea, shortness of breath, and severe stomach pain. Symptoms can range from mild to severe and typically occur two to six hours after consuming products with alpha-gal.

"Alpha-gal syndrome is an important emerging public health problem, with potentially severe health impacts that can last a lifetime for some patients," Dr. Ann Carpenter, and epidemiologist and lead author of one of the CDC studies, said in a 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," she added.

In one of the CDC studies, the team surveyed 1,500 health care professionals including general practitioners, pediatricians, internists, nurse practitioners and physician assistants.

The survey results showed 42% of the participants had never heard of AGS and 35% said they were "not too confident" in their ability to diagnose or manage AGS patients. Only 5% said they were "very confident" in their ability.

Two-thirds of the health care providers surveyed said clearly defined guidelines on how to diagnose and manage AGS would be helpful. The report's authors described the limited knowledge among providers as "concerning," especially due to the increasing number of AGS cases.

"Improved [health care provider] education might facilitate a rapid diagnosis of AGS, improve patient care, and support public health understanding of this emerging condition," the authors wrote.

In another study, the CDC looked at tests between Jan. 1, 2017 and Dec. 31, 2022 to determine how quickly cases of AGS have increased since 2010.

From 2010 to 2018, more than 34,000 suspected cases were identified. However, over the 2017-2022 study period, some 357,000 tests were submitted, resulting in just over 90,000 positive results.

The number of new cases increased by about 15,000 each year during the five-year study period, with most cases occurring in the Southern, Midwestern, and Mid-Atlantic U.S., the CDC found.

"The burden of alpha-gal syndrome in the United States could be substantial given the large percentage of cases suspected to be going undiagnosed due to non-specific and inconsistent symptoms, challenges seeking healthcare, and lack of clinician awareness," Dr. Johanna Salzer, senior author on both CDC studies, said in a statement. "It's important that people who think they may suffer from AGS see their healthcare provider or an allergist, provide a detailed history of symptoms, get a physical examination, and a blood test that looks for specific antibodies (proteins made by your immune system) to alpha-gal."