Chris Rose lost ten years of his health—not to mention his gallbladder—to a single tick bite. The tick bit in 2010 and Rose, now a 50-year-old network engineer in Chapel Hill, N.C., thought little of it at the time.
“It was one of those lone star ticks,” he says, “and I just picked it off me. It wasn’t a big deal.”
Before long, however, Rose began developing crushing chest pains, abdominal discomfort, diarrhea, and other symptoms. Doctors screened him for heart disease, irritable bowel syndrome, and gallstones, and even removed his gallbladder to see if that might ease the intestinal symptoms. But nothing worked, and the symptoms persisted for a decade.
Finally, in 2020, he visited Dr. Sarah McGill, a gastroenterologist at the University of North Carolina. She performed a colonoscopy and prescribed a round of antibiotics—to no avail—and then, as Rose recalls, McGill took a blood sample and said, “‘I want to test you for something. It may be a fluke, but we’ll see what happens.’”
The next day, McGill called Rose with a diagnosis. “You’re allergic to red meat,” she said.
What Rose was suffering from was a little-known condition called alpha-gal syndrome, an illness transmitted by the bite of a tick that has recently taken a blood meal from a deer. Deer, like all mammals except for humans, carry a sugar called alpha-gal in their bodies, and the tick stores microscopic traces of the sugar in its salivary glands. When it bites a person, the tick injects alpha gal into its victim, which can cause an allergy to red meats and even dairy products.
“Three quarters of my alpha-gal patients can recall a tick bite preceding their symptoms,” McGill says. “One woman was so sensitive to red meat that simply the smell of frying bacon caused her to rush to the bathroom with symptoms.” That trace amount of alpha gal in the mucus membranes of her nose was all it took to set off an allergic reaction.
Tick bites are most commonly associated with Lyme disease, which is carried by the black-legged tick and afflicts about 40,000 Americans each year, according to the U.S. Centers for Disease Control and Prevention (CDC). And with climate change leading to milder winters and longer summers, tick season is lengthening in parts of the U.S., especially in the Northeast. Making matters worse, white-tailed deer—the main source of food and transportation for ticks—have lost their fear of humans and the built environment and are regularly showing up in gardens and backyards, bringing the black-legged tick even to people who avoid the woods.
“White-tailed deer are the keystone host for the reproduction of these ticks, and the deer are in more places than ever before,” says Thomas Mather, professor of public health at the University of Rhode Island and director of the school’s Tick Encounter Resource Center.
But it’s not just Lyme that should have us wary of ticks. The CDC lists 21 other tick-borne diseases that lurk in the woods and grasses. Here are a few of the tick-related diseases experts urge people to look out for.
Alpha gal syndrome
Researchers are still working to determine how common alpha-gal syndrome is nationwide, but the condition varies widely by geography. According to McGill, antibody levels to the alpha-gal sugar are present in 20% to 25% of people in North Carolina and Missouri, for example, while in Boston they’re as low as 1%. That means plenty of people have been exposed to the molecule—likely through ticks—without knowing it. A 2021 study found that up to 3% of the U.S. population may carry alpha-gal antibodies—though often asymptomatically—with active cases most common among people living in the south, east, and central part of the country. But the U.S. is not alone. “Alpha-gal has been described in many parts of the world as well,” says McGill, “including Australia, Africa, and Europe. In those places, other ticks might be responsible, while in the U.S., it’s the lone star tick.”
One of the lingering mysteries of alpha-gal is why it takes a tick-bite to transmit the syndrome. If the sugar is present in mammal flesh, why don’t we contract the allergy simply by eating meat?
“We’re still working on the mechanism of transmission,” says CDC medical epidemiologist David McCormick. “There’s some research that suggests it may be related to compounds in tick saliva, but that hasn’t been definitively identified yet.” Adds McGill, “We don’t think people become sensitized through the gastrointestinal tract very easily. The skin is much more allergy prone.”
One of the most common tick-borne illnesses after Lyme, anaplasmosis is caused by a bacterium spread by the black-legged tick, and the disease is on the march. “The number of cases reported to the CDC have been increasing steadily,” says McCormick, “from 348 cases in 2000 to 5,762 in 2017.” Symptoms include fever, headache, muscle pain, and chills—all common across many tick-borne diseases—and the treatment of choice is the antibiotic doxycycline. About 1% of patients—especially older people, very young children, or people with compromised immune systems—can develop severe disease, such as encephalitis (brain inflammation) and require hospitalization.
Another increasingly common tick-borne disease—affecting up to 2,500 Americans per year—babesiosis is caused by a parasite spread by the black-legged tick. Like Lyme disease, it is common in the Northeast, but also in the Midwest, especially in Wisconsin and Minnesota. Its symptoms are similar to those of anaplasmosis, and in some cases, infected people may have no symptoms at all. The disease is treated by a combination of antibiotics and anti-parasitic drugs, and while the medications are usually effective, there are exceptions.
“If a person is immunocompromised or does not have a spleen—lost to either injury or surgery—the disease can be severe,” says CDC epidemiologist Megan Swanson. “In those cases, there can be complications that can lead to death.”
The lone star tick and the black-legged tick are both vectors for ehrlichiosis, a bacterial infection that is on the rise. The U.S. recorded just 200 cases in 2000—then more than 2,000 in 2019. Headache, chills, and fever are the most common symptoms. As with most bacterial tick infections, the treatment of choice for ehrlichiosis is the antibiotic doxycycline. While about 1% of reported cases were fatal, approximately half of reported cases required hospitalization.
Ehrlichiosis is especially pernicious because of its range. It appears in the most common tick-borne disease regions of the Northeast and Midwest but is also in South Central states including Missouri, Arkansas, Tennessee, Mississippi, North Carolina, and Virginia. “Because we have that additional tick,” says McCormick, “there’s a lot of additional cases.”
Rocky Mountain spotted fever
Rocky Mountain spotted fever (RMSF) is transmitted by three ticks: the American dog tick, the Rocky Mountain wood tick, and the brown dog tick. That gives it a range across most of the U.S., with up to 5,000 cases reported each year. In addition to fever and headache, RMSF can cause nausea, vomiting, stomach pain, muscle pain, and a signature rash. Caused by a bacterium and treated by doxycycline, the disease is the most deadly of the tick-borne illnesses, with an untreated mortality rate of up to 25%. That makes it especially important to be vigilant for symptoms, especially the telltale rash, which usually appears within two to four days of infection and can appear either as red splotches or pinpoints.
Still, “up to 60% of patients may not develop a rash until very late in their infection,” warns McCormick. “So if you’ve had a tick bite and you have a fever or headache, I strongly encourage people to seek medical attention so they can be evaluated for Rocky Mountain spotted fever.”
Powassan virus disease
Another disease with two multiple vectors, Powassan is transmitted by the black-legged tick, the squirrel tick, and the groundhog tick, with a range in the Northeast and throughout the Great Lakes region. Caused by a virus transmitted by the tick, the disease may take a month to incubate before symptoms—including fever, headache, vomiting, and muscle weakness—occur. A handful of cases can also lead to inflammation of the brain and spinal cord. Antibiotics do not work against viruses, and no effective antivirals have yet been determined to treat the disease. The best course of treatment in cases that do not require hospitalization for brain inflammation, according to the CDC, is rest, fluids, and over-the-counter pain medications. The only upside: Powassan is rare, with annual cases nationwide measured in the low dozens. But those cases can be serious. If Powassan results in encephalitis, its mortality rate can be as high as 15%.
How to protect yourself
The same precautions protect against all tick-borne diseases. Experts recommend using insect repellant containing DEET when venturing into the woods, conducting a full body tick check on yourself and your pets when you return from potentially tick-infested areas, showering right after returning from spending time outdoors, and immediately washing the clothes you wore and drying them on high heat for at least 10 minutes to kill any ticks.
Remember, too, that ticks are not only found in the wild. “Most persons who acquire tick-borne infections acquire them close to their homes,” says McCormick. “Even when you’re outdoors just gardening, you need to be thinking about it. These are infections people acquire where they live, work, and play.”
Corrections: The original version of this story misstated the dangers of ehrlichiosis. Fatalities, not just hospitalization, occur in about 1% of cases. The story also misstated the ticks that transmit Powassan disease. They are the black-legged tick, the squirrel tick and the groundhog tick, not just the black-legged tick and the groundhog tick.
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