The lone star tick's bite can release an antibody into its victims that makes them allergic to alpha-gal, a sugar found naturally in mammals. CDC

COLUMBIA, Mo. — It was a just a few pieces she sneaked off a pot roast that sent Chris Richey of Millersburg, Mo., to the hospital. She was covered in hives, her hands and arms “fire truck” red, itching so badly she was scratching the skin off. “This allergy is so weird,” she said. “It’s turned my life upside down.” Doctors had misdiagnosed her early reactions as a stomach virus or the flu, but recent research has validated what her own research had already uncovered: Richey is living with an allergy to red meat, likely brought on by a tick bite she suffered barely a year ago. She is one of what researchers estimate could be tens of thousands of people who have developed an allergy to alpha-gal, a sugar found naturally in mammals. Researchers believe the allergy is linked to bites from the lone star tick, a species named after its native range of Texas and the single white spot on its back. After being bitten, some victims carry a type of immunoglobulin E (IgE) antibody that, in turn, causes the allergic reaction to alpha-gal.

A lone star tick bit Richey, 58, in August 2012 while she was sitting with her husband in the shade of their apple tree in rural Missouri. She now carries the IgE antibody to alpha-gal. Her life hasn’t been the same since.

“I don’t want another reaction. That’s just too scary,” she said. “I can’t even begin to tell you how it makes you feel.”

Unexpected discovery

Thomas Platts-Mills, a professor of medicine and a researcher at the University of Virginia, discovered the connection between lone star tick bites and the alpha-gal allergy in 2006. He had been asked to investigate why some cancer patients were having a severe allergic reaction to the drug cetuximab, even though they had never been exposed to it before.

It turned out the patients who had a reaction already had the IgE antibody to alpha-gal, which is also found in cetuximab. Platts-Mills and his colleagues began to theorize about the origins of the antibody and noticed that the patients who carried it lived in rural parts of the South and Midwest, where ticks are common. “It had nothing to do with cancer,” Platts-Mills said. “It had everything to do with rural Tennessee, rural North Carolina, rural Virginia, (etc.). It wasn’t people who lived in the middle of the cities. It was the people who were living in the villages who really had this antibody.” Platts-Mills’ team’s first study, in 2008, described 24 cases. Within two years, they knew of 1,000. Patients exhibited reactions from eating beef, pork, venison, lamb — there was even a case of a reaction to squirrel meat reported at the University of Virginia clinic. Other products that come from mammals can trigger reactions as well. Richey has to have her medicine custom made because some pill casings contain gelatin, which comes from cows or pigs. Dairy is also out of the picture for her, since alpha-gal can show up in milk. She knows of another victim who had to cut out her favorite raspberry-filled pastries because the artificial flavoring is made with castoreum, a chemical that comes from the anal scent glands of the North American beaver.

Chris Richey's life was turned upside down after she suffered a lone star tick bite that left her allergic to meat and other animal products. Courtesy Chris Richey “What is so bothersome to me is the cross-contamination issue and all the hidden ingredients,” Richey said.

Anything containing, or that has come in contact with, a product from a mammal is a danger to people living with the alpha-gal allergy, Richey said. Not to mention that having to switch to a near-vegan lifestyle can add up at the supermarket checkout counter. “You’ve got to think, and double think, and think some more. It gets tiring,” she said. “It’s Russian roulette. The next time I have to get a tetanus shot, I don’t know what’s going to happen because I don’t know what’s going to be in it.”

Richey isn’t alone, and the numbers are growing. “We get daily emails from people who want to know about their tick bites and their reactions,” Platts-Mills said. “There’s no doubt that there are thousands of cases.” Lone star ticks have spread beyond the middle South in the last 20 years, having been reported as far north as Wisconsin and as far east as Maine. They tend to follow white-tailed deer, their host of choice, whose population has also been growing across the country, said Susan Little, a professor of veterinary parasitology at Oklahoma State University. The white-tailed deer population has exploded in recent years, with a Cornell University study (PDF) attributing the increase to changes in habitat, "including reversion of abandoned farm fields to forest, and shifts in human population to rural and suburban areas."



This map from 2011 shows the spread of the lone star tick, which originated in Texas. CDC

Lone star ticks need warm, humid environments to survive. Little said recent above-average temperatures combined with habitat change could be fueling the increase. When there are more shrubby plants and ample leaf litter, she said, not only do deer have more to eat, but there are more places for ticks to live and survive. One way people can protect themselves from ticks, Little said, is to put pets on tick-control medicine so they can’t bring the ticks into the home or close to people. “Every dog should be on tick control. Every dog, every month, all year long,” she said. “Having the dog treated (for ticks) will really protect the whole family.”

The lone star tick is an aggressive species. Instead of waiting for its host to walk by like most tick species, this one will actively pursue it. Females can lay up to 7,000 eggs at a time, and the lone star is the only tick in the United States that can bite humans when it’s still a larva, Little said. That’s how Platts-Mills got the alpha-gal allergy himself. In 2007, after hiking in the Blue Ridge Mountains, he found nearly 200 lone star larvae on his leg after they burrowed through his sock. He discovered his allergy that year when he broke out in hives after eating lamb at a conference in London.

'Allergy from hell'

For 16-year-old high school student Austin Lemieux of Bee Springs, Ky., adjustment to his alpha-gal allergy has been hard. His first reactions started a year ago, when he broke out in hives during football practice.

Despite taking great caution, Shauna Hensley Gravil said her 16-year-old son Austin Lemieux has accidentally eaten things he shouldn't have and had severe reactions. Courtesy Shauna Hensley Gravil One of the biggest changes was at lunchtime. If his school is serving only burgers or hot dogs, Lemieux could end up eating just an apple before football practice. At home there’s been an equally drastic change. “It has changed our whole family,” said Shauna Hensley Gravil, Lemieux’s mother. “I have to be careful with how I cook, and there have been a few times he accidentally has eaten something he shouldn’t have, and had a reaction.” Reactions typically occur three to four hours after exposure, unusual for most food allergies. Some people who carry the antibody show no symptoms, while some get hives and others even go into anaphylactic shock, a life-threatening allergic reaction that can cause the throat to swell shut. This danger is heightened by the fact that the reaction is delayed. “We think it’s perfectly possible that people have died,” Platts-Mills said. “Certainly people living on their own, especially at night. Nobody would know what happened. Within a few hours after death, you don’t see any signs of the hives.”