On a camping trip nearly three years ago at the Nulhegan River in the Northeast Kingdom, Casey Gianfagna and his buddy ate a late-night snack of burgers while hanging out with family and friends. He felt fine when he went to bed but woke up in the middle of the night with a terrible headache and stomach cramps.

"I was on fire," said Gianfagna, 34, an emergency room nurse who lives in Huntington. "I ran out to the outhouse. I vomited. I had some diarrhea, and then I went back to bed."

The next morning, Gianfagna ate a breakfast burrito made with bacon. After a while, he was back at the outhouse, vomiting and sick. At the time, Gianfagna was a nursing student and emergency room technician. He attributed his sudden illness to eating contaminated, rare hamburger meat. He'd never before gotten sick from eating red meat.

A couple of weeks later, Gianfagna was working on his house when he took a break for a burger at the Hindquarter in Huntington. A few hours later, he became ill with symptoms including a headache, nausea, vomiting and diarrhea. He also felt "hot, hot, hot," he said.

Gianfagna looked in the mirror and saw that he was "red as a fire truck" and covered in hives: on his head, under his armpits, spreading across his stomach and down his legs. He was home alone. He called his wife, Alison, an herbalist, and told her he thought he was having an allergic reaction.

"To what?" she asked.

"I don't know," he told her. "I just had a burger."

Alison thought it could've been caused by a tick bite. She knew that a lone star tick could trigger an allergic reaction to red meat, a condition called alpha-gal syndrome.

Gianfagna took Benadryl to quell his symptoms. But when he and Alison arrived at the University of Vermont Medical Center's emergency room, he was still "feeling pretty awful," he said.

"When someone comes in with an allergic reaction, you get a lot of attention," said Gianfagna, who works in the center's ER. "Deep down, I was a little bit afraid," he admitted. "I was also confident in my peers that I would be taken care of."

A quick assessment determined that his airways were open. He was given an IV with steroids and an antihistamine, monitored for a few hours, and referred to an allergist.

At Timber Lane Allergy & Asthma Associates in South Burlington, Dr. Edward Kent did skin tests and blood work, Gianfagna recalled. The results indicated that he was allergic to red meat. A blood test showed he was "grossly positive for [alpha-gal]," Gianfagna said, "which points all arrows to the lone star tick."

Kent spoke with Seven Days about alpha-gal syndrome in general. For privacy reasons, he did not talk about a particular patient.

"You can think of it like immunization," Kent said of the tick bite. "The tick inoculates you through its saliva secretions with this molecule that's called alpha-gal." The person can then develop allergic antibodies that remain in their system on cells called mast cells, he said.

"They're sitting there, armed and ready to go off," Kent said. "And they will go off whenever you're exposed to alpha-gal. Once you've developed an allergic antibody, you're primed to have an allergic reaction."

Alpha-gal is a carbohydrate found in red meat, dairy and products that contain mammal meat, including certain antibiotics, cosmetics and gelatin. A carbohydrate allergen is unusual, Kent said: "Allergens tend to be proteins." The type of allergic reaction depends on the amount of exposure, he said.

Symptoms can include nausea, hives, itchy throat, swollen tongue and vomiting, and they usually occur several hours after exposure. This distinguishes alpha-gal from other allergens, such as a bee sting or peanuts, which typically cause symptoms in a matter of minutes, Kent said.

It's unclear why the onset is delayed with alpha-gal syndrome. It's possible that the carbohydrate is linked with lipids in food and takes longer to be absorbed, Kent said. He advises people who think they have alpha-gal syndrome or who have experienced symptoms consistent with it to see an allergist.

"It's worth stating that you really need to be careful with ticks, period," Kent said. "And you cannot be too careful. People are well aware of other tick-borne diseases. This is an oddity, and you don't want to have it.

"There's no clear evidence that alpha-gal can be carried by other ticks," Kent continued. "But I think it's likely it can be."

The Vermont Agency of Agriculture, Food and Markets recently conducted a survey to look for lone star ticks. Volunteers looked for the tick on 107 wild turkeys that had been shot by hunters. That type of tick "favors turkeys," said Eliza Doncaster, the agency's vector management coordinator.

No lone star ticks were identified on the birds examined at wildlife checkpoints in six counties, she said. Only one tick was found on any of the turkeys: a black-legged tick on a bird in Addison County. The study indicates there is no breeding population of lone star ticks in Vermont, according to Doncaster.

"We were really surprised that we didn't find any," she said. "But I'd rather find none than a bunch."

The results provide useful baseline information. "If we redo this survey in a few years, we might find something different," Doncaster said.

The lone star tick, as its name indicates, is from the southern part of the country. But in the past two decades its "distribution, range and abundance have increased," including in the north and east, according to the Centers for Disease Control and Prevention.

Doncaster noted that lone star ticks have been identified on occasion in Vermont since the early 2000s. Experts believe they come on migratory birds, she said. In the early 2000s, about half a dozen were found on dogs with no travel history. A few were discovered in the spring of 2018 in a tick surveillance program. And in 2019, a person in Waterbury submitted a tick to state officials that was identified as a lone star, she said.

That's the year when Gianfagna, who hadn't left the state, developed alpha-gal syndrome. He never saw the classic rash associated with a tick bite, but he remembers a lesion on his inner thigh that was itchy and persistent.

"I've had ticks on me many times before, but only one or two that have been embedded and engorged," he said. "I've taken those off, no problem, and I didn't associate them with any kind of adverse reaction."

Gianfagna has eliminated red meat and dairy from his diet in favor of a predominantly plant-based diet, plus chicken and fish. He said he has to be very careful in restaurants, where he can't be certain of all the ingredients.

At work in the ER, Gianfagna said, the staff routinely sees people with tick-related ailments in the spring through fall. He thinks an annual physical should include blood work to check for tick-borne diseases. People should be aware of alpha-gal syndrome and take note if they become ill hours after eating red meat, he said.

"It has impacted my life so profoundly," Gianfagna said. "No one's ever heard of it, nor do they believe it. They question if I'm being factual or if I'm bullshitting them. I can tell you with 100 percent certainty that it's real."

Tick Avoidance Tips

Lyme disease is the most common tick-borne disease in Vermont, according to Natalie Kwit, the State of Vermont's public health veterinarian.

Lyme is an infectious disease transmitted by black-legged ticks, which are particularly active in late spring, early summer and fall, she said. Most human infections occur in the summer, when ticks are in their nymph stage. They're abundant and small, about the size of a poppy seed.

"They're the driver of disease," Kwit said, "compared to adults in the fall."

Kwit recommends taking precautions to minimize the risk of acquiring Lyme and other tick-borne infections: The goal is prevention.

Avoid tick habitats, such as wooded or brushy areas and high grass. If you are in the woods or in a field, stick to the center of trails.

On your skin, use a tick repellent registered with the U.S. Environmental Protection Agency.

Treat clothing with permethrin, a readily available insecticide that makes ticks unable to bite and can kill them. (Every year, Kwit treats two sets of clothing with permethrin; she wears them while gardening and hiking.)

Wear long pants, long-sleeved shirts and light-colored clothing; this provides protection from ticks and makes it easier to spot them.

Talk to your veterinarian about treating your animals with tick prevention medication.

Check yourself and your dogs for ticks before coming inside. Dogs are "tick magnets" because they often accompany their owners on walks in woods and parks. If they're off-leash, they can run through tick habitats.

If you have outdoor cats, check them for ticks when they come in.

When you come inside, put your clothes in the dryer on high heat for 10 minutes.

Take a shower within two hours of being outside; unattached ticks will come off, and attached ticks can be removed.

Make checking for ticks a daily habit. If you find one (or more), remove it from your body. The Vermont Department of Health advises people to call a doctor if they develop symptoms of a tick-borne infection.

"It's good practice anywhere you go," Kwit said of tick checks. "The black-legged tick is so prevalent here in Vermont."