美国国家公共电台 NPR--CDC warns about red meat allergy caused by some tick bites

CDC warns about red meat allergy¹ caused by some tick bites

Transcript²

Red meat fans beware.

The Centers for Disease Control and Prevention warns that alpha-gal syndrome³ — a tick-borne illness that causes a red meat allergy — is an emerging public health concern.

There have been more than 90,000 suspected cases documented between 2017 and 2022, yet nearly half of clinicians have never heard of the condition, according to a pair of CDC reports released on Thursday.

Because many providers aren't aware of alpha-gal syndrome, or AGS, which also requires a diagnostic test, the agency estimates that as many as 450,000 people may have been affected⁴ since 2010.

Scientists first connected the dots between red meat allergies⁵ and tick bites more than a decade ago, when they identified patients who got allergic⁶ reactions such as hives or anaphylaxis after eating beef or pork. Most had been bitten by Lone⁷ Star ticks.

Now, doctors' understanding of these allergies has evolved.

"What's new is that we have patients who really just have GI symptoms," explains Dr. Sarah McGill, a gastroenterologist at the University of North Carolina. McGill says some alpha-gal syndrome patients feel sick to their stomachs after they eat red meat, but never develop more typical allergic symptoms, such as a rash, swelling⁸ or trouble breathing.

McGill has co-authored new guidance for the American Gastroenterological Association to raise awareness⁹ about the GI-only onset¹⁰. She has diagnosed AGS in people who experience abdominal¹¹ pain, diarrhea, nausea¹² or vomiting¹³ about 2 to 6 hours after eating red meat.

That's exactly what happened to Randy Rayborn, 72, who lives in a rural community in Caswell County, North Carolina. "I figured it was food-poisoning," Rayborn recalls thinking after his first alpha-gal attack in the fall of 2019. "I woke up in the middle of the night with severe pain and nausea. I had to rush to the restroom," Rayborn recalls.

He describes the episode as "the most violent upheaval¹⁴" he'd ever experienced.

Deer and ticks are prevalent near Rayborn's home. He recalls pulling several ticks off his body in the months before his illness began, but he didn't realize the bites had triggered the illness. Nor did he imagine that the hamburgers or bacon he'd eaten had anything to do with it.

When he had a similar attack a few weeks later, he went to see his doctor, who referred him to McGill. A blood test showed he had Immunoglobin E, or IgE antibodies to alpha-gal, the sugar molecule¹⁵ that he was exposed to from the tick bites, suggesting he was positive for the allergy. "I'd never heard of it," Rayborn says, so he was very surprised.

McGill advised him to eliminate all red meat from his diet. "I miss bacon, I miss hamburgers, " Rayborn says. But after suffering through such painful episodes, "I don't miss them that much," he says. He remains¹⁶ symptom-free after several years on the diet.

Alpha-gal is a sugar molecule found in most mammals, including cows, lambs and pigs. It can also be found in the saliva¹⁷ of ticks. Humans don't make alpha-gal, so it's foreign to us, explains Dr. Scott Commins, an allergist at the University of North Carolina in Chapel¹⁸ Hill. When tick saliva goes through a person's skin and transmits alpha-gal it can be a potent¹⁹ inflammation trigger.

"Our immune system can be tricked into making an allergic response to this sugar," says Commins. Then, after a person is sensitized to alpha-gal, they can get a reaction every time they eat red meat. Alpha-gal can be found in beef, pork, lamb, rabbit, deer meat as well as other products from mammals including milk and gelatin, according to the CDC.

Commins has published a new research paper on tick bites and the risk of developing the alpha-gal allergy. People who get multiple tick bites (four or more) and spend a lot of time outdoors in wooded areas are at higher risk.

And the new recognition that alpha-gal syndrome leads some people to have only GI symptoms, without any traditional allergic symptoms, is a paradigm²⁰ shift. "It was a surprise," he says. Blood tests show that these patients have the same allergic antibodies as other AGS patients. "We did not know that we were missing these patients," Commins says.

During her medical training as a gastroenterologist, McGill says she was taught that allergies don't present with GI symptoms alone. But her clinical experience treating patients who didn't experience any hives or rashes led her to a different conclusion. "This flies in the face of what I learned about GI distress²¹ and allergies," McGill says.

Her change in thinking came after she saw a patient, similar to Randy Rayborn, who had experienced several episodes of nausea and GI distress. Each time it happened a few hours after eating a hamburger. "I did an endoscopy on that patient and it was normal," McGill says. But a blood test showed the patient was positive for AGS.

"I started checking for it more often," McGill says and she identified a string of patients who were also positive for alpha-gal antibodies. She advised all of them to go on the Alpha-Gal Elimination²² Diet.

A chart showing the sequence of the red meat allergy caused by some tick bites.

Early in the pandemic, when her endoscopy lab was shut down, she had time to do some research and check in with patients she'd diagnosed with AGS. She found that patients who had eliminated red meat told her they felt better. They also reported getting sick again if they went off the elimination diet. "I was surprised," she says. It was a confirmation²³ that her diagnosis²⁴ had been correct, and that avoiding these foods was an effective treatment.

Cases of alpha-gal syndrome have been concentrated in southeastern states, but the range extends from New York and Iowa to Texas and Florida. There have been cases reported on every continent (except Antarctica), and doctors say other types of ticks, beyond the Lone Star tick, may cause the syndrome.

A report in the New England Journal of Medicine, documents the case of a 47-year-old man in Ann Arbor²⁵, Michigan who stumped²⁶ doctors in the E.R. who were not familiar with the condition.

In the new guidelines for gastroenterologists, McGill and her colleagues say it's important for GI doctors to be aware of alpha-gal Syndrome and "be capable of diagnosing and treating it in a timely manner," pointing to the importance of the elimination diet. The evidence from recent studies show roughly 75% of AGS patients improve when they follow an alpha-gal–avoidance diet.

1 allergy   

n.(因食物、药物等而引起的)过敏症

参考例句：

• He developed an allergy to pollen.他对花粉过敏。
• The patient had an allergy to penicillin.该患者对青霉素过敏。

2 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

3 syndrome   

n.综合病症；并存特性

参考例句：

• The Institute says that an unidentified virus is to blame for the syndrome. 该研究所表示,引起这种综合症的是一种尚未确认的病毒。
• Results indicated that 11 fetuses had Down syndrome. 结果表明有11个胎儿患有唐氏综合征。

4 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

5 allergies   

n.[医]过敏症；[口]厌恶，反感；（对食物、花粉、虫咬等的）过敏症( allergy的名词复数 )；变态反应，变应性

参考例句：

• Food allergies can result in an enormous variety of different symptoms. 食物过敏会引发很多不同的症状。 来自辞典例句
• Let us, however, examine one of the most common allergies; hayfever. 现在让我们来看看最常见的变态反应的一种--枯草热。 来自辞典例句

6 allergic   

adj.过敏的，变态的

参考例句：

• Alice is allergic to the fur of cats.艾丽斯对猫的皮毛过敏。
• Many people are allergic to airborne pollutants such as pollen.许多人对空气传播的污染物过敏，比如花粉。

7 lone   

adj.孤寂的，单独的；唯一的

参考例句：

• A lone sea gull flew across the sky.一只孤独的海鸥在空中飞过。
• She could see a lone figure on the deserted beach.她在空旷的海滩上能看到一个孤独的身影。

8 swelling   

n.肿胀

参考例句：

• Use ice to reduce the swelling. 用冰敷消肿。
• There is a marked swelling of the lymph nodes. 淋巴结处有明显的肿块。

9 awareness   

n.意识，觉悟，懂事，明智

参考例句：

• There is a general awareness that smoking is harmful.人们普遍认识到吸烟有害健康。
• Environmental awareness has increased over the years.这些年来人们的环境意识增强了。

10 onset   

n.进攻，袭击，开始，突然开始

参考例句：

• The drug must be taken from the onset of the infection.这种药必须在感染的最初期就开始服用。
• Our troops withstood the onset of the enemy.我们的部队抵挡住了敌人的进攻。

11 abdominal   

adj.腹（部）的，下腹的；n.腹肌

参考例句：

• The abdominal aorta is normally smaller than the thoracic aorta.腹主动脉一般比胸主动脉小。
• Abdominal tissues sometimes adhere after an operation.手术之后腹部有时会出现粘连。

12 nausea   

n.作呕，恶心；极端的憎恶(或厌恶)

参考例句：

• Early pregnancy is often accompanied by nausea.怀孕期常有恶心的现象。
• He experienced nausea after eating octopus.吃了章鱼后他感到恶心。

13 vomiting   

吐

参考例句：

• Symptoms include diarrhoea and vomiting. 症状有腹泻和呕吐。
• Especially when I feel seasick, I can't stand watching someone else vomiting." 尤其晕船的时候，看不得人家呕。”

14 upheaval   

n.胀起，(地壳)的隆起；剧变，动乱

参考例句：

• It was faced with the greatest social upheaval since World War Ⅱ.它面临第二次世界大战以来最大的社会动乱。
• The country has been thrown into an upheaval.这个国家已经陷入动乱之中。

15 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

16 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

17 saliva   

n.唾液，口水

参考例句：

• He wiped a dribble of saliva from his chin.他擦掉了下巴上的几滴口水。
• Saliva dribbled from the baby's mouth.唾液从婴儿的嘴里流了出来。

18 chapel   

n.小教堂，殡仪馆

参考例句：

• The nimble hero,skipped into a chapel that stood near.敏捷的英雄跳进近旁的一座小教堂里。
• She was on the peak that Sunday afternoon when she played in chapel.那个星期天的下午，她在小教堂的演出，可以说是登峰造极。

19 potent   

adj.强有力的，有权势的；有效力的

参考例句：

• The medicine had a potent effect on your disease.这药物对你的病疗效很大。
• We must account of his potent influence.我们必须考虑他的强有力的影响。

20 paradigm   

n.例子，模范，词形变化表

参考例句：

• He had become the paradigm of the successful man. 他已经成为成功人士的典范。
• Moreover,the results of this research can be the new learning paradigm for digital design studios.除此之外，本研究的研究成果也可以为数位设计课程建立一个新的学习范例。

21 distress   

n.苦恼，痛苦，不舒适；不幸；vt.使悲痛

参考例句：

• Nothing could alleviate his distress.什么都不能减轻他的痛苦。
• Please don't distress yourself.请你不要忧愁了。

22 elimination   

n.排除，消除，消灭

参考例句：

• Their elimination from the competition was a great surprise.他们在比赛中遭到淘汰是个很大的意外。
• I was eliminated from the 400 metres in the semi-finals.我在400米半决赛中被淘汰。

23 confirmation   

n.证实，确认，批准

参考例句：

• We are waiting for confirmation of the news.我们正在等待证实那个消息。
• We need confirmation in writing before we can send your order out.给你们发送订购的货物之前，我们需要书面确认。

24 diagnosis   

n.诊断，诊断结果，调查分析，判断

参考例句：

• His symptoms gave no obvious pointer to a possible diagnosis.他的症状无法作出明确的诊断。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做一次彻底的调查分析。

25 arbor   

n.凉亭；树木

参考例句：

• They sat in the arbor and chatted over tea.他们坐在凉亭里，边喝茶边聊天。
• You may have heard of Arbor Day at school.你可能在学校里听过植树节。

26 stumped   

僵直地行走，跺步行走( stump的过去式和过去分词 )； 把（某人）难住； 使为难； （选举前）在某一地区作政治性巡回演说

参考例句：

• Jack huffed himself up and stumped out of the room. 杰克气喘吁吁地干完活，然后很艰难地走出房间。
• He was stumped by the questions and remained tongue-tied for a good while. 他被问得张口结舌，半天说不出话来。