A Mysterious Meat Allergy Caused By A Tick Bite Is Now “An Emerging Public Health Concern”

Here’s what you need to know about this often underdiagnosed food allergy.

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A live specimen of the lone star tick (A. Americanum) in a lab in Morrill Hall at the University of ...
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In the early 2000s, a new cancer drug was on the horizon. Called cetuximab, it was an immunotherapy created for metastatic colorectal cancer. Pharmaceutical companies ImClone Systems and Bristol Meyers Squibb ran clinical trials across the US for the drug in 2004. Soon enough, it became apparent something was very wrong.

Some participants developed allergic reactions — hives or the fatally worse anaphylaxis — shortly after a single dose of cetuximab. It was unclear what was causing this mysterious reaction, and stranger still, it seemed to be particularly affecting individuals living in the southern US. Finally, scientists landed on a culprit: alpha-gal, a sugar found in red meat and dairy products, as well as some pharmaceutical products, including cetuximab. Later research found people allergic to alpha-gal were likely to have been bitten by ticks, the parasites transmitting the sugar with every bite.

Over the last decade, alpha-gal syndrome, as the allergic reaction is now known, has impacted an estimated 110,000 Americans. The actual burden could be much more — nearly half a million Americans by some estimates — as many clinicians are unfamiliar with the condition, according to two new studies released last week by the Centers for Disease Control and Prevention.

“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,” Johanna Salzer, senior author on both papers and veterinary medical officer at the CDC, said in a press release.

The studies found that out of 1,500 healthcare providers surveyed, only five percent felt very confident they could treat or diagnose a patient with alpha-gal syndrome, 35 percent weren’t confident, and 42 percent had never heard of the condition before. This knowledge gap presents a grave concern as alpha-gal syndrome is becoming “an emerging public health concern, with potentially severe health impacts that can last a lifetime for some patients,” Ann Carpenter, Salzer’s co-author and an epidemic intelligence service officer at the CDC, said in the press release.

Here’s what you need to know about this strange food allergy.

What causes alpha-gal syndrome?

Similar to Lyme disease, alpha-gal syndrome is associated with tick bites, particularly the southern-state dweller lone star tick although other tick species haven’t been ruled out.

Scientifically as galactose-alpha-1,3-galactose, alpha-gal is a sugar dotting the cells of non-primate mammals including cows, pigs, and sheep. When a lone star or other tick chomps down on an alpha-gal-wielding mammal, the parasite ingests the molecule, carries it, and transmits it to its next unsuspecting meal ticket.

Since humans don’t carry alpha-gal, our immune systems recognize it as foreign the moment it enters our bodies. For some folks, the immune system overreacts when it sees alpha-gal, producing a torrent of special antibodies called IgE. These antibodies interact with other immune cells to produce chemicals like histamine, which leads to inflammation and other allergy symptoms.

What are the symptoms and is it treatable?

Unlike most food allergies that typically occur within minutes, alpha-gal symptoms are delayed, appearing anywhere from three to eight hours after eating red meat, dairy products, or pharmaceutical products containing the sugar. This delay makes timely diagnosis difficult. Common symptoms ran the gamut from mild — hives, itching, swelling, nausea or vomiting, respiratory issues — to severe with anaphylaxis, which is life-threatening and requires immediate medical attention.

Not all individuals with the condition will develop symptoms every time they ingest something containing alpha-gal, the CDC’s Salzer told the New York Times. Why isn’t exactly clear and also makes timely diagnosis tricky.

Diagnosing alpha-gal syndrome is pretty straightforward with a blood test determining whether an individual has those anti-alpha-gal antibodies. However, there is no definitive treatment or cure for the food allergy. Symptoms are kept at bay by eliminating foods or pharmaceutical products containing alpha-gal.

The good news is that if you avoid foods containing the sugar, then alpha-gal syndrome can be fairly manageable and does not seem to affect long-term health. According to the Mayo Clinic, symptoms may lessen or disappear over time, especially if you avoid repeated tick bites. You may be able to go back to eating mammal-derived food products within a year or two.

Is alpha-gal becoming more common?

With climate change upending seasonal patterns and ticks expanding their territories, the illnesses these parasites bear are on the rise. As of 2018, ticks accounted for 77 percent of reported vector-borne diseases, according to the CDC. Among these diseases, Lyme disease accounted for 82 percent of reported cases — nearly doubling between 1991 and 2018. Cases of infectious diseases associated with ticks like spotted fever rickettsioses, babesiosis, and anaplasmosis have also been on the rise.

Understandably, the trend sounds very concerning, especially if you’re living in an area where alpha-gal syndrome is considered common such as the South, Mid-Atlantic, and Midwestern states.

One of the new studies published in the CDC’s Morbidity and Mortality Weekly Report found that positive tests for alpha-gal syndrome have also steadily increased. Based on data collected between 2017 and 2022 from a commercial lab that, up to 2021, was the only one conducting antibody tests in the US, cases increased annually from 13,371 in 2017 to 18,885 in 2021. Roughly 20,000 cases had been identified in an earlier study, yielding a total of 110,000 suspected cases from 2010 to 2022. (The larger number of up to nearly half a million cases in the CDC report is an estimate, based on a survey of health care professionals.)

Your best bet, according to the CDC, to prevent the strange meat allergy is to protect yourself against tick bites. Be aware of your surroundings, especially when frequenting grassy, bushy, or wooded areas known for ticks or interacting with animals that may have come in contact with the parasite. Wear long-sleeved clothing, spray yourself with EPA-registered insect repellent, and make sure to check your gear, body, and outdoor-going pets for ticks or tick bites.

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