Ticks are the worst.

And they’re very effective at being the worst. They’re responsible for 77% of diseases in the US passed to humans by blood-feeding critters, like Lyme disease and spotted fevers.

But the weirdest tick-borne disease out there is a lot stranger. The only common manifestation is an allergy to red meat. It’s called Alpha-Gal Syndrome, or AGS.

And, it is spreading. [♪ INTRO] Alpha-gal syndrome is kind of a baby in the tick-borne disease world. It was only confirmed in 2007. And its main sign is that it causes you to develop an allergic reaction to a sugar called alpha-gal.

It’s actually one of only two known allergies where the thing you react to is a sugar, instead of a protein. Almost all mammals make this alpha-gal sugar, but the gene is inactivated in humans and some other primates, so we don’t produce it. We don’t fully understand the mechanism of how ticks cause Alpha-gal syndrome, but we think it has to do with their spit.

Ticks carry all kinds of nasty stuff in their saliva, like the bacteria that causes Lyme disease. It’s also chock full of proteins that have an outer coating of a whole bunch of alpha-gal sugars. The main hypothesis right now is that when they snack on us, those alpha-gal covered proteins enter our body.

And because humans don’t produce this sugar, it’s treated as a foreign invader, triggering our immune systems to see it as a threat. That causes the body to produce antibodies called IgEs, which are then primed to recognise alpha-gal as a threat in the future. And that future is inevitable for eaters of red meat, since, as we said, basically all other mammals make that sugar too.

Which means that the next time the unsuspecting tick-bite victim digs into a burger or hot dog, the antibodies spot the sugar and tell immune cells to release chemical signals, triggering an allergic reaction. This can present in a few different ways, from uncomfortable rashes to something as severe as anaphylaxis. And unlike in other allergic reactions, where anaphylaxis is almost immediate, Alpha-gal related anaphylaxis can be delayed for hours after eating meat.

Despite the delay, this is still a serious, potentially-fatal reaction, so getting a quick and correct diagnosis is super important. But that isn’t as simple as it sounds. One survey found that nearly half of health care practitioners in the United States hadn’t even heard of alpha-gal syndrome, and less than a third felt comfortable diagnosing it.

The lack of widespread knowledge on this new illness is a pretty big issue. The CDC estimates that more than 450,000 in the United States might have developed the life-threatening allergy since 2010, many of whom won’t even realize they have the illness. The majority of these cases are found in the eastern United States, which is also where we find the Lone Star tick, a species of tick named for the single white dot on its back.

The Lone Star tick is responsible for a plethora of nasty diseases like ehrlichiosis, Heartland virus disease and southern tick-associated rash illness. And, alpha-gal syndrome. But this disease isn’t unique to the Lone Star tick or even the United States.

From South Africa to Sweden, Alpha-gal syndrome has been spread by different but equally nasty species of ticks in countries on every continent but Antartica. Now, if you’re one of the growing number of people across the globe with alpha-gal syndrome but you still have a hankering for bacon, not all is lost. In 2020, the FDA approved a line of “GalSafe” domestic pigs for both food and therapeutic use.

These pigs don’t express alpha-gal on their cells, so shouldn’t trigger an allergic reaction. It might just be easier and cheaper to cut mammal meat out of your diet, though. But people with alpha-gal syndrome aren’t just missing out on steak.

It can cause reactions to other products containing alpha-gal like dairy and gelatin. And the bigger concern with Alpha-gal syndrome is the potential for reactions to pharmaceutical products that contain alpha-gal, which are much more complicated to avoid than meat or dairy. Take Cetuximab, a drug used to treat colorectal cancer and squamous-cell carcinoma of the head and neck.

Back in 2007, people in areas like Tennessee and North Carolina were reported to show negative reactions to Cetuximab at much higher rates than reported elsewhere. We now know that people in these areas are much more likely to report being bitten by the fiendish Lone Star tick, and those adverse reactions were caused by Alpha-gal syndrome. Unfortunately, beyond avoiding the triggers, there’s no cure for Alpha-gal syndrome.

Although the symptoms can lessen or even disappear over time, there’s no guarantee of that happening. So your best bet to keep enjoying the occasional steak is to try and avoid tick bites altogether. Which is becoming increasingly difficult to do.

For instance, Lone Star ticks have been found in the southeastern United States for over a century, but in the past few decades they‘ve been expanding their territory northward. As temperatures increase due to the climate crisis, conditions become much more favourable for ticks to survive and reproduce. So we’re seeing more ticks than ever, and a longer active season for them to find humans to snack on.

All of this means the potential for more tick-borne disease, including Alpha-gal syndrome. So I guess if you do want to continue eating that McDonald's hamburger the best thing to do is to follow the ABCs of tick prevention. A - Avoid places ticks love to hide out, like tall grasses and leaf litter.

B- bug spray! And lots of it. The CDC recommends bug spray containing 30% DEET or picaridin.

And C - clothing. Cover up with long clothes, and tuck your pants into your socks if you plan on wading through long grass. These are all simple but effective ways to stay safe against ticks and avoid a future allergy to cheese.

And, given the damage ticks can do, this is good advice even if you’re a vegetarian. A big thank you to our patrons on Patreon for making this video possible. Your support helps us keep these lights on and also other lights throughout this building and also mainly to pay the people who make this stuff.

Aside from that warm fuzzy feeling, our patrons also get access to, like, a ton of neat perks, like a monthly patron-only podcast, blooper reels–very fun–and our private Discord server. If all that sounds up your alley, head on over to Patreon.com/scishow to learn more. [♪ OUTRO]