This vampire "tick" can cause deadly food allergies
This is a rare food allergy.
People have seizures several hours after eating red meat, and even have severe anaphylactic shock in their sleep.
The problem is red meat?
No, there is another "culprit" behind it.
August 9-15, 2021 is the sixth "China Allergy Week" in China. Doctors from the Allergy Department of Peking Union Medical College Hospital will reveal the midnight terror caused by "vampires" here.
Rare food allergies caused by eating red meat
Case replay: Since 2009, the United States and Australia have successively reported rare cases of red meat allergy. Patients have been able to eat meat happily for decades, but suddenly from a certain day, they were eating red meat for several hours. Later, symptoms such as general itching, urticaria, edema of the face and larynx, and difficulty breathing appear. In more severe cases, sudden drop in blood pressure, shock, convulsions, fainting, and even incontinence may occur.
Since then, Sweden, Spain and other places have also reported this rare case of food allergies.
This kind of typical immediate allergic disease, onset in adulthood, with acute onset, severe symptoms, and potentially fatal, often requires emergency treatment in the emergency room.
Doctors found that, different from the usual clinical manifestations of food allergy, the above-mentioned food allergic reactions have very peculiar clinical features: allergic symptoms appear only 3 to 6 hours after eating red meat foods such as pork, beef or lamb; in addition, cause The allergen caused by the symptoms is a special sugar substance-alpha galactose, which is so far the only food allergy caused by sugar substances.
Behind the shock was it "ticked"
What causes rare food allergies?
After detailed epidemiological investigations and laboratory examinations, scientists found that the pathogenesis of this peculiar disease is different from almost all other food allergies-delayed anaphylactic shock caused by red meat allergy is related to the patient's previous tick bite. This is so far the only food allergy caused by the bite of parasites on the body.
The dominant tick species in different countries and regions are different, such as Amblyomma americanum in the Americas, Ixodes scoparium in Europe, Ixodes pertussis in Australia, and Haemaphysalis longhorned tick in China, but all of them have been reported to cause red meat allergies.
So far, this disease is still very rare, with only more than 200 cases reported internationally.
In 2010, the Allergy Department of Peking Union Medical College Hospital confirmed the first case of red meat allergy caused by the bite of Haemaphysalis longhorned tick in Asia.
Up to now, Concord has confirmed more than 10 such cases.
Ticks are veritable "vampires"
Ticks are blood-sucking arthropods widely distributed throughout the world.
Unlike cat fleas, ticks are quite dangerous blood-sucking creatures.
The only food source for ticks is the blood of other animals. Whether they are female or male ticks, juvenile ticks or adult ticks, they all need to feed on blood to survive.
Under normal circumstances, ticks or hidden dormant on the grass and trees of the hills, or lodge in the fur of domestic animals or wild animals.
The ticks before blood-sucking may be as big as a needle tip, and it is difficult to detect its existence with the naked eye; the ticks after blood-sucking swell like full soybeans, their volume and weight increase by dozens or even hundreds of times compared with those before blood-sucking.
In order to survive, the tick is also quite fighting, and has evolved a "stunt".
At the end of its first pair of feet, there are special receptors: Haller’s organs, which can sense the host’s chemical information, heat, and airflow to help it find its host. Once it finds a suitable "victim", it will Will climb to the top of the plant, stretch out his arms, ready to give a "death hug" to passing animals at any time.
The tick’s saliva contains a special "narcotic", which makes you neither itchy nor painful when sucking blood, and quietly eats a meal on your body without knowing it.
In most cases, the bite of a tick that does not carry the pathogen can cause the host to lose a small amount of blood.
In extreme cases, a large number of ticks biting the same animal can cause blood loss and death.
The deadly “kiss” of ticks that carry pathogens can transmit a variety of serious diseases, such as “forest encephalitis”, Q fever, and rickettsial disease. The notorious “Lyme disease” is also caused by tick bites. Caused by.
After sensitization, "red meat" is a passerby
The focus of this article is that tick bites can cause a small number of victims to produce specific IgE antibodies, leading to severe allergic reactions after eating red meat.
Why is red meat allergic after being bitten by a tick?
It turns out that there is a kind of alpha galactose in the saliva of ticks. It is this substance that caused the victims to suddenly develop allergies to meat such as pork, beef, and lamb.
To put it simply, the process is like this: When a tick bites a human, the alpha galactose in the saliva will enter the victim's blood along with the saliva, and then be detected by the human immune system.
The immune system treats alpha galactose as an invader and produces special, targeted specific IgE antibodies, which are "recorded" in this way.
After these people who have been "labeled" by IgE eat red meat again, the alpha galactose structure contained in the red meat is "recognized at a glance" by the special antibodies pre-stored in the body, which then activates a series of intense immune responses in the body. A series of allergic symptoms such as skin and mucous membranes, respiratory tract, gastrointestinal tract, and cardiovascular system appeared immediately.
Although the story is simple, it is clinically difficult to detect and diagnose this disease.
First of all, because patients often have late-onset allergies, they will not develop until a few hours after eating, so it is not easy for patients or doctors to discover the causal relationship.
When performing an allergen test, it is difficult to find this allergen in a conventional skin test, because it is not the protein allergen in the traditional allergic reaction that causes the allergy, but the alpha galactose in the allergen preparation process. The class will be greatly depleted and the content will decrease, resulting in false negative skin tests.
We found that once a patient is sensitized, in addition to the red muscles, the animal’s various internal organs, skin, tendons and other "meat surroundings" can no longer be eaten, although these are not "red meat."
In this way, ticks are still a "food killer."
After being bitten by a tick, some people will say goodbye to twice-cooked pork, sauced beef, Dongpo pork knuckle, lamb offal, braised boil, lion's head, roasted sausage, ham, fried steak, lamb skewers, roast suckling pig, roasted whole lamb...
How to prevent being bitten by a tick?
As a meatless foodie, do you start to tremble when you see this place?
It doesn't matter, as long as we take the necessary protective measures, there is a way to prevent this from happening.
Please keep the following guide:
1. The activities of ticks have significant seasonality (spring and summer). In spring and summer, try to avoid getting involved in woods and grasses with a high density of ticks;
2. When walking in an area with ticks, it is best to fasten the cuffs and trouser legs to prevent the ticks from getting into the clothes, and try to wear light-colored long-sleeved trousers for inspection at any time;
3. Spraying drugs to repel ticks on clothes, DEET, which is effective for mosquitoes, also has a good repelling effect on ticks;
4. Ticks that crawl on the body generally do not bite people immediately, so after going home, you should carefully check your clothing and body for ticks.
If you take your pet to a place such as grass, you also need to check whether there is a tick attached to the pet.
What to do after being bitten by a tick?
Once you have been bitten by a tick, you must pay special attention to it.
Never pinch it with your hands or use folk remedies such as fire, because any damage and irritation to the tick may allow more pathogens to flow into the body.
The correct way is to use pointed tweezers to clamp the mouthparts of the tick (most of them are buried in the skin at this time) or as close to the skin as possible, and then carefully and slowly pull it out in the vertical direction.
Do not throw away or destroy the plucked ticks, but should be kept in a bottle for the doctor to identify and examine.
After being bitten, find a hospital that can handle tick bites as soon as possible for further treatment.
If you remove the tick within a day after the tick bite and seek medical attention in time, the probability of contracting the disease is very low.
Text/Wen Liping (Peking Union Medical College Hospital)