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Strange meat allergy caused by ticks may be easier to catch than we thought



A Female Lone Star Tick or Amblyomma americanum.
Picture: Amanda Loftis, William Nicholson, Will Reeves, Chris Paddock (CDC)

One of the strangest side effects of a tick bite – a new allergy to red meat – could be even easier to get than previously thought. New research from this weekend suggests that bites from certain ticks can trigger the allergy, no matter what they have recently bitten. The finding could reverse a widespread theory that ticks may have recently absorbed the blood of other mammals before they can transmit a meat allergy to humans.

The allergy is caused by an immune reaction to a sugar molecule called alpha-gal. Most mammals have alpha-gal in their muscles, but not humans and other primates. For some reason, the bite of certain ticks can sometimes cause persistent hypersensitivity to things that contain alpha-gal, especially red meat, including beef, pork, and sometimes dairy products.

This hypersensitivity reaction works almost exactly like a typical food allergy with symptoms like hives, respiratory distress or even a life-threatening anaphylactic shock. But it's the only known food allergy to a sugar instead of a protein and the symptoms only appear after an hours exposure. Sometimes the allergy seems to occur years after the first bite.

We know the Alpha-Gal syndrome for a long time, as it is called. In fact, this is one of the main reasons that important organ transplants from nonhuman animals like pigs just can not work for us. But it took decades before the first cases of alpha galaxies in the alpha-gal region were documented until the late 1980s, when scientists could officially track them down for tick bites. And we still do not understand so much about the condition.

One of these mysteries is why exactly ticks can cause the syndrome. The lead author of the new research, Scott Commins, an adjunct professor of medicine and pediatrics at the University of North Carolina, was one of the first physicians to report cases of red meat allergy a decade ago. A widely held theory that he and others had is that ticks pick up alpha-gal from a previous blood meal, such as a dog, deer, or mouse. Her saliva, which is now filled with alpha-gal, then sensitizes the person who bites her.

To test this theory, Commins and his team did a simple experiment. First, they took samples of human blood and filtered out their native immunoglobulin E (IgE), the antibodies that protect certain types of foreign invaders and also cause an allergic reaction to an allergen. Then they administered the blood with donated plasma (filled with IgE antibodies) from people with and without the syndrome. Finally, they introduced saliva from four types of ticks: the Lone Star, Hirsch, the Gulf Coast and the American dog. The saliva samples were from ticks that had not been fed with alpha-gal containing blood and were not fed.

Previously, the tick most commonly associated with red meat allergy in the US was the Lone Star tick. And not unexpectedly, the saliva of this tick could trigger an immune response (based on the level of a particular white blood cell called the basophile) 40 times stronger than normal in alpha-gal sensitized blood. But also saliva from the deer tick, the main vector of Lyme disease and other tick-borne diseases in the US, triggered a reaction. Most worrying was that the non-fed tick saliva of both species also triggered a reaction in sensitized blood.

The results presented last weekend at the annual meeting of the American Academy of Allergy, Asthma and Immunology (AAAAI) are preliminary (and have not yet been published in a peer-reviewed journal). However, they provide evidence for another well-known theory that the tick itself, not its last meal, causes the syndrome.

"These new data suggest that the latter [theory] may be correct: something is in the saliva," says Commins told Gizmodo. "All humans have an existing response to alpha gal, which would be consistent with a model in which tick bites easily divert the existing immune response to switch to an allergic response."

It is almost certain that there are chances of every single tick bite of a Lone Star or any other tick that triggers the allergy is quite low. However, we do not know how low this risk currently is (according to a previous Commins estimate, 5,000 people might be affected in the US alone). And if ticks are the main cause, regardless of their diet, the time window for an allergy-causing bite is obviously higher.

The Red Meat Allergy is just one of the nightmare health problems caused by ticks – problems that, at least in the US, the climate should warm up over time. There were nearly 60,000 cases of Lyme disease in 2017, compared to 22,000 in 2004. But the actual annual number of Lyme cases is around 300,000, according to CDC.

How a Red Meat Allergy Could Be A rare tickborne complication, it is one of many that are likely to become more common. There is currently no treatment or cure for the syndrome (some sufferers may eventually eat meat again, but not all). This means that there is really only one way to prevent this from happening at all, says Commins, though not every summer walker is in danger.

said. "The people in the west and northwest of the US seem to have little or no risk. Beyond these areas, people should be alert and diligent with tick bite provisions. Most of all, we worry about the southern and eastern areas of the US. "


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