One night in 2008, Deborah Fleshman awoke in her bed to find that her legs had turned beetroot red. Welts, some a foot wide, had appeared along her torso.
Ms. Fleshman, a nurse at the time, had earlier that evening hosted a cookout at her home in Greenwood, Del., a town of about 1,000 people 25 miles south of Dover. She drank a couple of beers. She ate a cheeseburger.
Hours later, she told her worried father, “I feel like I’m dying.”
Ms. Fleshman, now 60, is among the thousands of Americans diagnosed with alpha-gal syndrome, an allergic reaction to mammal meats like pork, beef and lamb, which growing evidence shows can be triggered by a tick bite.
“It feels like you’re on fire, and then it feels like you slept with a cactus,” she said. “The itching is unbearable.”
Researchers have traced the syndrome to the lone star tick, named for the signature white splotch, or “lone star,” on females’ backs. They’re historically found in the southern United States, but increasingly, these arachnids are being spotted in parts of the Midwest and the Northeast.
The tick’s territory is expanding, thanks in part to global warming, say scientists. With more hot days each year, the ticks, which thrive in warm and humid conditions, have more time to feed on their hosts and reproduce. At the same time, alpha-gal diagnoses appear to be rising.
“What we’re now seeing is a wide open door for ticks to continue expanding their range further northward; bringing more people into the fold of the arthropod-borne diseases,” said Michael Raupp, a professor emeritus in entomology at the University of Maryland.
The Centers for Disease Control and Prevention estimates that between 2004 and 2019, the total number of tick-borne diseases in the United States more than doubled. In the meantime, other devastating pests that were previously constrained by cooler temperatures — like the dengue virus-carrying tiger mosquito, or the cabbage-munching harlequin bug — have also marched forth beyond their historic ranges.
“We’re venturing into uncharted waters in so many dimensions with climate change,” Dr. Raupp said.
By nature, ticks are travelers; they attach themselves to hosts in order to suck their blood, hitching a ride in the process. Scientists say an explosion in the population of the white-tailed deer, their primary host, has also helped them to spread.
According to some maps, the lone star tick has advanced as far west as parts of Nebraska, and as far northeast as Maine. Climatic conditions are also suitable for the ticks to establish populations along the coast of Washington, Oregon and California, other models indicate.
Scientists first began noticing an allergic reaction to alpha-gal in 2006, but it was not until several years later that they understood it was likely caused by the bite of the lone star tick. By 2012, it had already been found in 39 states, according to one study.
“The spatial distribution of the species has definitely increased by at least 30 to 50 percent in the last half a century,” said Ram Raghavan, an assistant professor in epidemiology and disease ecology at the University of Missouri, who has mapped the lone star tick’s spread. According to his research, the ticks are expected to continue to shift and expand their range; both to the north and west.
Goudarz Molaei, the director of a state-run tick and pathogen surveillance program in Connecticut, said that the lone star tick has firmly established itself in at least two counties in the state. “Because of climate change, what lands in our region, stays,” he said.
The lone star tick bite can result in several other illnesses, including the recently identified Heartland virus disease and Bourbon virus disease, both of which can lead to fever, fatigue and in some cases hospitalization, and even death. Unlike the blacklegged tick, it cannot transmit Lyme disease, though one study indicates that the blacklegged tick may also be implicated in spreading alpha-gal.
Alpha-gal syndrome is triggered by a complex sugar called galactose-alpha-1, 3-galactose, or alpha-gal, for short. The sugar is found in most mammals, but not in fish, reptiles, birds or humans. When the lone star tick feeds, alpha-gal is spread through its saliva, exposing the host’s immune system to the sugar. For some people, this triggers an overactive immune response the next time they encounter it.
More than 34,000 people in the United States have tested positive for alpha-gal syndrome, according to a 2021 paper. A map publicly generated by individuals who say they suffer from the condition indicates that the syndrome may have spread as far as Washington and Hawaii, though this does not mean the sufferers were bitten by ticks in those states.
Though the conditions present mildly for some, others suffer hives, swelling, wheezing, diarrhea or even anaphylaxis, which can be fatal. Unlike many other allergic conditions, the symptoms may take several hours to appear after consuming meat products, making the syndrome difficult to diagnose.
“It’s never predictable,” said Jennifer Platt, an adjunct professor in public health at the University of North Carolina at Chapel Hill and a co-founder of the nonprofit Tick-Borne Conditions United. “I know people that spend the night in the emergency room parking lot, waiting for a reaction,” she said, adding, “I think of alpha-gal syndrome as Lyme 2.0.”
“There are so many parallels in terms of patients being told by their providers that it’s all in their head,” Dr. Platt said.
Even after treatment, some symptoms of Lyme disease, including pain and fatigue, can linger for months, according to the C.D.C. But some medical experts remain skeptical of this chronic version of the disease, disagreeing about its presentation, diagnosis and treatment.
Some sufferers of alpha-gal — especially in states where the ticks have been thought to be less common — described the frustration of seeking a diagnosis and encountering disbelief from medical professionals.
In Ms. Fleshman’s case, it took more than seven years and about a dozen trips to the emergency room before she finally found out what was wrong. At one point, an infectious disease doctor told her she could not have alpha-gal syndrome, because there were no lone star ticks in the state of Delaware.
“I was livid,” Ms. Fleshman said. “Do you really think they read a sign that says, ‘Do Not Enter,’ and they listen?”
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