Tick-Related Meat Allergy Lurks Under the Radar, Unfamiliar to Many

Despite alpha-gal syndrome (AGS), or tick bite meat allergy, rising over the last several years and affecting many people in the U.S., many healthcare providers remained unsure about its diagnosis and treatment, CDC data showed.

An estimated 96,000 to 450,000 people in the U.S. have been affected by AGS since 2010, the large range accounting for undiagnosed people who went untested, reported Johanna Salzer, DVM, PhD, of the Division of Vector-Borne Diseases at the CDC, and colleagues, in the Morbidity and Mortality Weekly Report.

During that time, a total of 110,229 suspected cases were documented. And suspected cases have been rising in recent years, with 13,371 positive test results in 2017 increasing to 18,885 in 2021.

Meanwhile, a recent survey of 1,500 healthcare providers revealed that 42% of providers had not heard of AGS. About 35% of providers responded being “not too confident” that they could treat or diagnose a patient suffering from AGS, while only 5% reported feeling “very confident,” according to Ann Carpenter, DVM, of CDC’s Epidemic Intelligence Service, and colleagues, in survey results published alongside the study.

AGS is a condition in which patients develop an immunoglobulin E-mediated hypersensitivity to galactose-alpha-1,3-galactose (alpha-gal), an oligosaccharide commonly present in non-primate mammal meat. Allergen products include pork, beef, lamb, milk products, gelatin, and even some pharmaceuticals.

This is thought to be the result of bites from the lone star tick (Amblyomma americanum) found in the Eastern, Southeastern, and South-central U.S. However, other tick species have not been ruled out.

Common AGS symptoms include nausea or vomiting, severe stomach pain, difficulty breathing, and in some cases, anaphylaxis, which can be life-threatening. While some cases may resolve over time, particularly if a patient can prevent further tick bites, there is no official cure for the syndrome.

“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,” said Salzer in a press release.

It can take anywhere from 2 to 6 hours for AGS symptoms to develop following allergen consumption, and symptoms may be inconsistent, potentially making it difficult to diagnose.

Sarah Kelly McGill, MD, Msc, of the University of North Carolina at Chapel Hill, told MedPage Today that tick bites are generally common in her area, and many of her patients with AGS had experienced gastrointestinal symptoms only, without a rash or problems breathing. “They’re patients that, if I hadn’t diagnosed them [with AGS], they would be given a diagnosis of functional vomiting or irritable bowel syndrome, some disorder of gut-brain origin. It’s not readily apparent that they have a food allergy.”

“None of my patients thought that their symptoms were related to meat ingestion. I think it’s very hard for patients to figure this out because of the delay between when you eat something and when you get sick,” said McGill, who was not involved with the CDC report.

Scott Commins, MD, of the University of North Carolina at Chapel Hill, and a coauthor on both reports, suggested that existing societal and geographic disparities may also hinder AGS diagnosis and management.

“Allergists do not exist in every county and some patients would have to travel quite far to see a specialist. This probably contributes to a fair amount of undiagnosed cases,” Commins told MedPage Today in an email. “The new survey data suggests primary care providers may not be as well versed in recognizing and diagnosing AGS.”

Indeed, the CDC researchers reported that among survey respondents who said they were aware of the syndrome, 78% had not made a diagnosis of the condition in the last year.

Survey respondents were family practitioners, general practitioners, internists, pediatricians, nurse practitioners, and physician assistants who had opted in to a market research survey platform. For those aware of AGS, nearly half stated that they were not aware of which diagnostic tests are appropriate to request for AGS, one-third were able to correctly report that AGS can develop following a tick bite, and 58% provided appropriate counseling topics for AGS patients.

Overall, more than 60% of participants agreed that resources and guidelines regarding AGS diagnosis and management would be helpful.

Based on the available geographic data, suspected AGS cases were most common in the Southern, Midwestern, and mid-Atlantic Census Bureau regions. Suffolk County in New York and Bedford County, Virginia led the largest number of total suspected cases at 3,746 and 1,511, respectively. Charlotte County in Virginia and Muhlenberg County, Kentucky, saw the highest concentration of suspected cases per capita, at 12,273 and 6,107 per 1 million people per year, respectively, according to Salzer’s group.

The CDC investigators cautioned that the geographic study did not include all testing labs nationwide, and that an affected individual’s reported location may not have been where the culprit tick bite took place.

Furthermore, survey results may not be generalizable beyond the profile of providers on the survey panel.

“Alpha-gal syndrome is an important emerging public health problem, with potentially severe health impacts that can last a lifetime for some patients,” Carpenter emphasized in a press release. “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.”

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