Suffolk County’s distinction as the nation’s leading county for suspected cases of alpha-gal syndrome is the result of an uniquely potent combination of an invasive, aggressive species of tick, an abundant deer population and hundreds of thousands of people living alongside both.

The county recorded 3,746 suspected cases of alpha-gal syndrome from 2017 through 2022, more than any other county in the United States, according to an analysis by the Centers for Disease Control and Prevention. About 4% of all suspected cases identified nationally during that period were in Suffolk County.

The figures do not mean Suffolk had the nation’s highest per-capita rate. Several rural counties in Virginia and Kentucky were higher. But no county in America produced a larger raw number of suspected cases.

Dr. Erin McGintee — a Southampton allergist-immunologist who first identified alpha-gal syndrome on Long Island in 2011 and is one of the Northeast’s leading experts on the tick-associated allergy — said Suffolk’s numbers reflect both the prevalence of lone star ticks and the unusually close proximity of people to the animals that sustain them.

“You’re going to get alpha-gal when you have lone star ticks,” McGintee said. “The East End of Long Island, in particular — and now it’s spreading west — has always been a hotbed for ticks.”

‘They’ve sort of run rampant’

Alpha-gal syndrome is an allergy to alpha-gal, a sugar molecule found in most mammals but not in humans. In susceptible people, a tick bite can prompt the immune system to produce antibodies against the molecule. Those people may then experience an allergic reaction after eating beef, pork, lamb or other mammalian meat or encountering certain products made from mammals.

Unlike most food allergies, the reaction is generally delayed. Symptoms commonly emerge two to eight hours after eating, often awakening patients in the middle of the night with hives, itching, stomach cramps, vomiting or diarrhea. Severe cases can lead to anaphylaxis, a potentially fatal allergic reaction.

The lone star tick, named for the white dot on the adult female’s back, was once associated primarily with the South but is now firmly established on Long Island. McGintee said the species was barely present on the East End 30 or 40 years ago, but “they’ve sort of run rampant now.”

Rodents and deer

Suffolk is different from many Southern alpha-gal hot spots because large numbers of people live within that tick-friendly landscape. Rural woods, farms and preserved land are interspersed with subdivisions, playing fields, parks and backyards.

At the center of that environment is Suffolk County’s large white-tailed deer population. Deer are critical hosts for adult lone star ticks, while mice, squirrels and other small mammals help sustain the ticks during earlier stages of their life cycle.

“You need both the small rodents and the deer to perpetuate the life cycle of the lone star tick,” McGintee said.

Small rodents are common almost everywhere, she said, but deer are not. Suffolk’s deer have no natural predators.

“Deer are on our front lawns, they’re in our backyards, they’re on our baseball fields,” McGintee said. “So people are coming into contact with these ticks more.”

That cycle is unlikely to change soon. Neither a typical Long Island winter nor an occasional cold snap is enough to substantially reduce the tick population. McGintee said it would take a prolonged period of cold and dry conditions — something closer to a deep, dry freeze lasting weeks — to have a meaningful effect.

“I don’t know that we ever have winters that would qualify for that in a way that would impact the tick population,” she said.

The ‘most aggressive’ tick in town

More than any other tick on Long Island, the lone star tick actively seeks out potential hosts instead of waiting for them to brush by, according to Dr. Luis Marcos, director of Stony Brook Medicine’s Tick-Borne Disease Resource Center, who said the tick’s persistence has helped fuel its rapid expansion across Long Island.

“It is the most aggressive one among the ticks,” he said. “It actually starts crawling in the soil and can chase you. It comes to you.”

Combined with increasingly mild winters, Marcos said, that behavior has allowed the species to steadily expand northward while displacing the blacklegged, or deer, tick that historically dominated Long Island.

“We are seeing less diseases transmitted by deer tick and more diseases transmitted by lone star tick,” he said.

What’s more, the problem — once concentrated on the North and South forks — is moving west. McGintee said her earliest patients were overwhelmingly from the East End. During the past five years, she said she has increasingly seen patients from Port Jefferson, Stony Brook, Rocky Point, Smithtown and other communities farther west where deer have established themselves.

“It’s going to get worse in that I think that we’re going to see it spread to a wider territory.”

Marcos said the trend extends beyond alpha-gal syndrome itself. On parts of Long Island, lone star ticks now account for roughly 90% of the ticks his team encounters.

“That’s kind of amazing because the deer tick has been replaced.”

He expects the shift to become even more apparent over the next several years as surveillance data catches up with what physicians are already seeing.

“The cases of meat allergy are going to go up,” Marcos said.

That does not necessarily mean an ever-larger percentage of people bitten by lone star ticks will develop meat allergies. Many people produce alpha-gal antibodies after tick bites without ever experiencing an allergic reaction. A CDC study published this month found alpha-gal antibodies in nearly 12% of blood samples collected from donors in 12 states and Washington, D.C. In five states with established lone star tick populations, the average was approximately 24%.

But that does not mean one-quarter of the population has alpha-gal syndrome.

“A positive test does not make a diagnosis,” McGintee said.

That distinction is at the heart of what she described as a growing diagnostic problem.

‘The test is not sufficient to make a diagnosis’

McGintee identified her first Long Island case around 2011, when alpha-gal syndrome was barely recognized outside a handful of cases in the Southeast. At the time, the larger problem was that doctors did not know to look for it.

Now, she said, increased attention has created the opposite problem: Doctors are sometimes ordering alpha-gal blood tests as part of broad tick panels for patients who have fatigue, muscle aches or a recent tick bite but have never suffered an allergic reaction after eating meat. Some are then told to stop eating mammalian meat solely because antibodies were detected.

“I’ve seen people with alpha-gal IgE off the charts who can eat meat without having an allergic reaction,” McGintee said. “The test is not sufficient to make the diagnosis.”

She said alpha-gal testing should be ordered when a patient’s history suggests a delayed allergic reaction to mammalian meat, not simply because the person was bitten by a tick.

“You don’t identify a food allergy with a test; you identify it with a clinical history,” she said.

The consequences of overdiagnosis are not trivial. Patients may become frightened, radically restrict their diets and turn to online forums filled with inaccurate or exaggerated information.

Related: The East End’s growing threat from Lyme disease, alpha-gal and more

During the summer, McGintee said she may see two or three patients who probably do not have alpha-gal syndrome for every patient who does. In winter, she estimated that she sees five or six patients with positive tests but no clinically meaningful allergy for every likely genuine case.

She has evaluated more than 1,200 patients with concerns about alpha-gal, but she stressed that this does not mean all 1,200 had the syndrome. McGintee believes the increase in patients experiencing genuine allergic reactions is real. But she said the surge in suspected diagnoses has been driven even more heavily by testing.

“I think it’s both, but I honestly think the majority of it is more testing, more inappropriate testing,” she said.

‘Tip of the iceberg’

Marcos said that despite concerns about overtesting, he believes many Suffolk residents with alpha-gal syndrome have never been diagnosed simply because they’ve never sought treatment.

“This is just the tip of the iceberg,” he said. “Most likely there are 10 or 20 times more cases in Suffolk County.”

For those who do develop the syndrome, avoiding additional lone star tick bites is crucial. Alpha-gal antibody levels can decline over time when patients are not repeatedly bitten, and McGintee said she has seen patients who moved away from lone star tick territory eventually test at zero.

That path is far more difficult in Suffolk County, where the ticks, deer and people remain tightly bound together.

Meanwhile, according to Marcos, “there is another tick invading Long Island – the Asian longhorned tick. We are studying it at Stony Brook, and we don’t know whether that tick will replace the lone star tick, or can bring other diseases or infections beyond what we have here already.”