One bite from this parasite can make you allergic to meat forever

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Even if you’re a fully fledged member of PETA’s elite animal fan club, it’s hard to love parasites. No matter how many times we’re told that they are just part and parcel of the natural world, the thought of something burrowing into your flesh and slowly sucking you dry is enough to make anyone reach for the bug spray. It’s a sad fact that planet earth is full of horrific creepy crawlies that make the monsters from Alien look like bunny rabbits.

In certain parts of the world, there’s a very real risk that every time you step outside your front door you’ll end up with something horrible clamped to an exposed limb. Eventually, you might even get used to the idea of living in your very own horror movie. However, things get a whole lot more serious when these interactions with insectoid ne'er-do-wells extend beyond an itchy bite. In some cases, the world’s worst parasites can cause real damage.

In all of God’s rich parasitical tapestry, there is one species that we are perhaps more likely to encounter than any other. Ticks are, unfortunately for anyone squeamish, everywhere. Found on every continent except Antarctica, they flourish in warm, wet climates, making them a particular hazard in places where people like to go on holiday. Of the estimated 900 species around the world, most survive by drinking the blood of different mammals and birds. Some extend their eating habits to include us. This is not only disgusting but, in certain circumstances, can have a host of hideous side effects - all of which are more than capable of ruining your vacation.

You could write a book - and many have - on all the horrible things that can happen after a tick bite, but there is one particular species that can have a uniquely cruel effect. Spread across the Southeastern United States, Mexico and parts of South America, the lone star tick is more like a sick joke from a particularly vindictive Greek god than something that naturally evolved. A bite from this bug won’t kill you. In some cases, it might not do anything at all. However, if you’re particularly unlucky, there’s a chance that a bite from a lone star could make you completely allergic to meat. Forever.

The reaction is all to do with a complex chemical aversion to a carbohydrate known as alpha-gal. Present in most mammalian cells, alpha-gal is found in the protein membrane and is integral in forming cell structure. Humans, great apes and Old World monkeys, are not born with a natural aversion to alpha-gal. However, one bite from a lone star tick can cause the immune system to treat alpha-gal as an invading antibody, and trigger an aggressive response in the form of an anaphylactic allergic reaction. This can happen any time the person eats beef, pork or even dairy products.

Given our natural insulation from alpha-gal, scientists were for a long time baffled as to what could possibly be causing patients’ seemingly spontaneous meat allergies. Their work was made even more complicated by the fact that the reactions sometimes wouldn’t even present until between three to six months after the initial bite from a lone star. It wasn’t until a study from the University of Virginia in 2011 - when the lead researcher himself was accidentally bitten by a tick - that scientists slowly began to make the link.

Initially, it was believed that the condition could only be spread if the tick had recently feasted on another mammal before biting a human. This made the risk of becoming allergic relatively low. However, new research presented by The American Academy of Allergy, Asthma & Immunology suggests that the danger is much more present than we first thought. In actual fact, it seems as though the reaction is not caused by a hangover from a previous victim, but from the tick’s saliva itself. As researcher Scott Cummins said in an interview with Gizmodo: “All humans make an existing response to alpha-gal and these data would be consistent with a model where tick bites simply redirect the existing immune response to shift to an allergic one.” In lay terms, the risk is much greater than we previously thought.

Despite what might look like a pretty gloomy prognosis for any meat-loving Texas ramblers, there’s no need to call a national crisis just yet. Compared to other conditions, such as Lyme disease, cases of tick-induced meat allergy are relatively low. The CDC estimates that around 30,000 Americans contract Lyme disease every year, while only 5,000 are afflicted with alpha-gal. Nonetheless, the numbers are high enough that those who enjoy both steak and the great outdoors should take note. Being bitten by something small and many-legged is already bad enough before you realise that you’ll never be able to eat another burger.