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环球科学

户外被它被咬一口，你可能再也不能吃药丸、喝牛奶、吃烤肉｜科学60秒

环环球科学约 5 分钟

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蜱虫的咬，尚无解药

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小小蜱虫，大大伤害 @Unsplash
蜱虫，一种会在徒步时跳到你身上的小吸血鬼，它会传播一些严重甚至致命的疾病，例如在美国最常见的虫媒病（Vectorborne）莱姆病（Lyme disease）。
但除此之外，它还可能让你对红肉和奶制品过敏，准确来说，是患上“α-半乳糖综合征”（alpha-gal syndrome）：蜱虫叮咬会引起我们对半乳糖-α-1,3-半乳糖（galactose-α-1,3-galactose，简称α-半乳糖）的免疫反应。
除人类与部分猿猴外，α-半乳糖存在于大多数哺乳动物体内。少吃点红肉对地球来说似乎不是什么坏事，但这种过敏实际上会非常严重。如果不慎被孤星蜱虫（Amblyomma americanum）叮咬，你可能会在几周或几个月后对各种红肉产品，包括牛肉、羊肉、猪肉还有培根、香肠，以及牛奶、奶酪等乳制品，甚至是果冻和含有明胶的药丸，都！过！敏！不仅仅是不吃红肉就可以了……[查看全文]

This Tick Bite Makes You Allergic to Red Meat

Josh Fischman: On today's show, we're talking about ticks—and the nasty diseases these little blood-sucking vampires carry with them. One of them even makes you allergic to red meat and dairy!
[Clip: Show theme music]
Tanya Lewis: I am terrified of ticks. I like to go hiking in the Hudson Valley, but I always try to wear long pants or use insect repellant. And I check for ticks when I come home.
Fischman: You're really actually sort of like shaking terrified of ticks? Why?
Lewis: Well, I mean I especially worry about deer ticks because they carry Lyme disease. Those ticks are super common here in the Northeast.
What about you, Josh?
Fischman: Funny, I actually went to college not that far from Lyme, Connecticut where that disease got its name, and I wasn't that worried about it then. But now I've got this dog with this dense, black fur.
Lewis: Oh, you mean Kayla?
Fischman: Yep, good old Kayla. And it's very hard to see ticks in her fur because they're the same color. I once was brushing Kayla and I brushed one onto myself and I didn't see it for hours. Fortunately, it didn't bite me. It was just hanging out, dangling from my leg.
Lewis: I'm glad it didn't bite you, because ticks are more than just a nuisance—they transmit serious and sometimes deadly diseases.
Lyme disease, for example, is probably the one we're most familiar with, and it's the most common vectorborne disease in the U.S.
Fischman: Vectorborne means what exactly?
Lewis: Any disease spread by insects that bite or suck our blood, like ticks, mosquitoes or fleas.
Lyme disease is primarily caused by a bacterium called Borrelia burgdorferi, which is transmitted by the bite of the blacklegged tick—more commonly known as the deer tick. This often results in a characteristic bull's eye rash, as well as flu-like symptoms like fever, headache, fatigue, and sometimes joint pain.
Fischman: Some people experience long-term chronic symptoms too, and those can include extreme fatigue or neurological issues.
Lewis: Yeah that's pretty awful. We actually know quite a lot about Lyme disease. Or at least more than other kinds of diseases spread by ticks. But today I want to talk about a different tickborne condition, which causes a particularly bizarre problem: an allergy to red meat, among other things.
It's called alpha-gal syndrome. The tick bite causes an immune response to a sugar called galactose-α-1,3-galactose.
Fischman: Okay Tanya, you get the hard science word of the week.
Lewis: I thought you'd like that. The sugar, called alpha-gal for short, is present in most mammals  except for humans and a few ape and monkey species.
Kersh: Alpha-gal syndrome is a tick-bite-associated allergic condition. We think people, after getting a tick bite, in the few weeks or maybe a couple of months after, they start having allergic reactions when they consume red meat or other products that contain the alpha-gal sugar.
Lewis: That's Gilbert Kersh, chief of the Rickettsial Zoonoses Branch at the CDC's Division of Vector-Borne Diseases. How's that for a title?
I talked to him a couple weeks ago for a story about alpha-gal syndrome. He co-authored a couple of recent CDC reports about how widespread this condition is and what doctors know about it.
Fischman: I'd never heard about this. A tick bite can make you allergic to hamburgers?
Lewis: Yeah, strange as that may seem. Something that makes people eat less red meat might not sound so bad for the planet. But it's actually quite severe.
Fischman: What kind of symptoms do people get?
Lewis:  They are really debilitating. The reactions include gastrointestinal symptoms like diarrhea and vomiting.
Fischman: And it's not just beef, right?
Lewis: Right—many mammalian products contain alpha-gal, like pork…
Fischman: Bacon? Sausages?
Lewis: Yup.
Fischman: Venison?
Lewis: Yup.
Fishman: Cheddar cheese? Regular milk?
Lewis: Yeah, dairy too. It's even in gelatin!
Fishman: So people with the syndrome could react to jello! And also, and maybe more importantly, pills like gel caps, which are made from gelatin.
Lewis: Yeah, that's the tricky part. It's not like you can just stop eating red meat and you'll be fine...[full transcript]

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论文信息

1. Thompson JM, Carpenter A, Kersh GJ, Wachs T, Commins SP, Salzer JS. Geographic Distribution of Suspected Alpha-gal Syndrome Cases — United States, January 2017–December 2022. MMWR Morb Mortal Wkly Rep 2023;72:815–820.

DOI: 10.15585/mmwr.mm7230a2

2. Carpenter A, Drexler NA, McCormick DW, et al. Health Care Provider Knowledge Regarding Alpha-gal Syndrome — United States, March–May 2022. MMWR Morb Mortal Wkly Rep 2023;72:809–814.

DOI: 10.15585/mmwr.mm7230a1

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