Why don’t I recommend you to eat raw pickled or raw water chestnuts?

Recently, pickled shrimp has become popular again! But it’s not because of its delicious taste, but some negative news: a netizen learned to make pickled shrimp, but unfortunately got food poisoning...

Picture丨@Boiling Point Moment

In fact, the netizen's poisoning may not have much to do with the seasoning, but was caused by the ingredients not being fresh enough. Among food safety issues, parasitic infections cannot be underestimated. In addition to the raw pickles mentioned in the news, many common foods that are not properly handled, and even aquatic plants, can also cause parasitic infections. Save this article quickly, and don't fall for it in the future!

Liver fluke: a ghost in freshwater fish and shrimp

Friends who travel to the southern coastal areas may have eaten freshwater fish and shrimp foods such as sashimi , sashimi porridge , and hot pot . However, there is a very common parasite in freshwater fish - Clonorchis sinensis, also known as liver fluke, which is one of the parasites with the highest infection rate in China. Liver fluke disease has a history of at least 2,300 years in China.

The larvae of liver flukes parasitize in freshwater snails and freshwater fish and shrimps. The commonly eaten black carp, grass carp, silver carp, bighead carp, carp and crucian carp can carry them. After being eaten by humans, the larvae are excysted in the duodenum and crawl into the bile duct, and then the adult worms make their home in our bodies.

The life cycle of liver flukes. Humans are infected with liver flukes by eating parasitized freshwater fish. Liver flukes excyst in the human intestines and the adult worms eventually make their home in the bile ducts. | Human Parasitology / People's Medical Publishing House

Once liver flukes enter the human body, they can survive for a long time , some even for 20 to 30 years. The biggest harm it causes to the human body is that it can damage the liver, leading to a series of liver and gallbladder diseases such as cholecystitis, cirrhosis, and bile duct cancer. It is classified as a Class I carcinogen by the International Agency for Research on Cancer (IARC).

The most troublesome thing is that liver fluke is like a ghost, and it is difficult to detect even if infected . The early symptoms of liver fluke infection are not obvious, and unless it is an acute attack, it often takes several years for symptoms to appear. Moreover, the symptoms caused by liver fluke disease are very common, such as fatigue, stomach pain, loss of appetite, indigestion, abdominal pain, diarrhea, etc., so many people don’t know it is because of it when they are sick, and they are often misdiagnosed and the disease is delayed.

In order to pursue a fresh and tender taste, people may not have enough time to blanch freshwater sashimi before taking it out, which increases the chance of infection with liver flukes |

Eating raw freshwater fish is the most important factor causing liver fluke infection . In areas where people have the habit of eating raw freshwater fish (such as Guangdong), the infection rate of liver fluke is quite high. In recent years, the infection rate of parasites such as roundworms, hookworms, and whipworms has been declining, but the infection rate of liver fluke has been increasing in some areas (such as Guangdong) , largely because people in these areas like to eat raw freshwater fish.

At present, it is known that nearly 70 kinds of freshwater aquatic products can be infected with liver flukes . For example, a survey found that the infection rate of grass carp reached 75%, the infection rate of bighead carp in Nanhai District of Foshan City was 87%, and the infection rate of wheatear fish in Sanshui District was 100%. Therefore, we remind everyone not to eat freshwater fish and shrimp raw. In addition, when cooking freshwater fish and shrimp at home, you should also pay attention to separating raw and cooked cutting boards, knives, and containers to prevent cross contamination.

Fresh freshwater shrimp are directly marinated with wine to make drunken shrimp. Because there is no heating step, alcohol alone cannot completely kill liver flukes. If you like the taste of drunken shrimp, it is recommended to cook the shrimp thoroughly before marinating with wine | James Creegan / wikimedia

Bullfrogs are delicious, but beware of sparganosis

Bullfrogs are also a delicacy that many people like to try. However, bullfrogs may also carry parasites - sparganosis.

Plerocercoid is not the name of a parasite. It is a general term for the larvae of certain types of tapeworms at a developmental stage called the "mid-tapestomium", the most common of which is Sparganosis mansoni.

If the bullfrog you eat is not cooked well, you may be infected with sparganosis |

The adult worm of Spirometra mansoni is called Spirometra mansoni , which is a relative of the well-known pork tapeworm. The final hosts of Spirometra mansoni are mainly cats and dogs, and sometimes carnivores such as tigers and leopards. In the intestines of these animals, the adult Spirometra mansoni can parasitize for several years and produce a large number of eggs. These eggs enter the water with feces, hatch into larvae, and then enter the body of tadpoles along the food chain. As the tadpoles develop into frogs, the larvae also develop into sparganosis. If humans eat infected tadpoles or frogs, the larvae will enter our bodies.

Life cycle of Spirochete mansoni | Human Parasitology / People's Medical Publishing House

Pork tapeworm removed from a human body | wikimedia

Although humans are not the final host of Spirocera, they can also cause great harm to the human body, especially the sparganum, which can travel between different parts of the human body and cause damage all over the body . Diseases caused by sparganum are collectively called sparganosis , which can be roughly divided into five categories according to the site of onset: eye, subcutaneous, oral and facial, brain and internal organs.

In China, the incidence of ocular sparganosis is the highest, and the symptoms are quite terrifying. Patients will have lumps in their eyes and are accompanied by various severe discomforts. If the sparganosis invades the eyeball, it may even cause blindness . Sparganosis can also damage the human brain, and in the most serious cases, it can cause paralysis .

Incorrect consumption of frogs and snakes, such as eating frog or snake tissues without any processing , drinking snake blood, swallowing snake gall, eating cold snake skin, or drinking water contaminated by worm-carrying sword water fleas, can cause sparganosis infection. In addition, some people have a "strange" eating habit of swallowing tadpoles raw, which can also easily cause infection.

There is a folk remedy that believes that eating tadpoles raw can cure certain diseases, which is unfounded and there is also a risk of parasitic infection | westdene / Vegetable

In addition to eating, applying it on the skin can also increase the risk of sparganosis infection. In China, more than half of the people infected with sparganosis are infected by applying raw frog meat . Because frog meat has the effect of "cooling and detoxifying", many people apply raw frog meat on wounds or skin abscesses, which increases the risk of infection.

When eating snails, beware of fake ones

Snails are also a famous snack for late night snacks. However, many people often get parasitic infections due to eating golden apple snails by mistake. Here we especially remind everyone not to eat golden apple snails as field snails .

The golden apple snail (Pomacea canaliculata) is very popular in the Yangtze River area. The golden apple snail itself actually tastes bad and is not delicious at all, so few people eat it specifically. However, because it has no natural enemies and has a high yield, some unscrupulous merchants "switch it for a prince" and sell it as field snails, resulting in people being infected with a parasite - Angiostrongylus cantonensis.

The difference between the Golden Apple Snail and two common types of river snails: the Chinese round river snail and the Chinese round river snail | Claude & Amandine EVANNO

Angiostrongylus cantonensis, also known as rat lungworm, was first discovered in rats in Guangzhou by Chinese scholar Chen Xintao in 1933.

Angiostrongylus cantonensis | Punlop Anusonpornperm / wikimedia

Adults of this parasite live in the heart and lung tissue of rodents, and the intermediate hosts are mollusks such as the golden apple snail and the brown cloud agate snail. These mollusks are infected by ingesting feces containing larvae. Humans can be infected by eating uncooked or raw snails and other mollusks, frogs, toads, freshwater fish, shrimp, crabs, etc. that contain larvae of the Guangzhou roundworm, or by contact with food or water contaminated with infective larvae of the Guangzhou roundworm. The first case of Guangzhou roundworm disease in humans was discovered in Taiwan Province in 1994.

The golden apple snail is the intermediate host of the Guangzhou roundworm, and the nematodes can parasitize in the golden apple snail. If the food is not heated thoroughly or not cooked well, the nematodes can easily invade the human body and make people sick.

Although it is said that cooking thoroughly can avoid risks, can ordinary people ensure that it is cooked thoroughly? | Luke Nguyen

Being infected with Angiostrongylus cantonensis is a very painful process. Its most prominent symptom is severe headache , which may also cause nerve root pain, hyperalgesia, fever, nausea, vomiting, and even meningitis . If not treated in time, it may even lead to death . We remind everyone to be more careful when eating snails outside to avoid eating golden apple snails.

Eat water chestnuts raw, beware of ginger worms

Many people also go to the lake to pick lotus pods, water chestnuts, and water caltrops to eat. However, if you think that the hosts of parasites are limited to animals, you are wrong. Eating aquatic plants raw may also cause parasite infection .

There is a parasite whose main transmission medium is the stems and fruits of aquatic plants, such as water chestnuts, wild rice stems, lotus roots, large water caltrops and red water caltrops. This parasite is called Fasciolopsis buski, or simply Fasciolopsis buski.

Fasciola busulinae | CDC / wikimedia

This is a large trematode that parasitizes the human small intestine and can cause fasciolosis. The larvae of Fasciola busulinae will burrow into the flesh of aquatic plants. When people eat these sweet, crisp and juicy edible parts raw, or use their teeth to gnaw off the skin of these plants , they will eat the larvae of the fasciolinae into the intestines and cause illness. Once the fasciolinae enter the human body, they will cause necrosis and shedding of the intestinal mucosa, inflammation, edema, ulcers or abscesses, causing abdominal pain, diarrhea and other symptoms in the infected person. In severe cases, it can cause malnutrition or even death.

Life history of Fasciola brucei | Human Parasitology / People's Medical Publishing House

Human Fasciola pneumoniae is usually more common in adolescents, but in severely endemic areas, the infection rate is high in all age groups, which mainly depends on the chance of infection with Fasciola pneumoniae metacercariae. Investigations have found that eating raw water chestnuts, wild rice stems, water chestnuts and other aquatic plants , especially eating while picking water chestnuts, is very likely to cause infection with Fasciola pneumoniae.

Remember to cook water chestnuts thoroughly before eating | TheDarkCurrent / wikimedia

We remind you that even water chestnuts bought in town markets may contain live metacercariae. There have been cases of radix fasciatus metacercariae found in a water chestnut before. Therefore, we recommend that you try not to eat water chestnuts, water chestnuts, lotus roots and other aquatic plants raw. Even if you want to eat them raw, do not bite the skin with your teeth . Be sure to wash them thoroughly and soak them in boiling water for a few minutes or dry them in the sun for a day before eating. When you take your children to pick these aquatic plants, do not eat them while picking them.

Is it OK to eat raw seafood? Don't ignore Anisakis

After talking about so many parasites in freshwater food, many people will wonder, is there no parasite in seafood? In recent years, eating raw salmon fillets and oysters has become very popular.

Many people like to eat salmon sashimi, but there is still a risk of parasitic infection | Pixabay

Indeed, there have always been sayings that "parasites cannot live in seawater", "there are no parasites in marine fish", "you don't have to worry about parasites when eating raw marine fish", etc. However, this is not true. In fact, seawater is not a forbidden zone for parasites, and eating seafood is also likely to infect parasites .

There are many types of "parasites", and their living environments and hosts are very different. Although some parasites cannot live in seawater environments, there are many parasites that live on the surface or in the body of marine fish. Like other animals, almost every marine fish will be infected by parasites.

There are many types of marine fish parasites known to date. Fish diseases caused by these parasites, such as Cryptocaryonosis, Myxosporidiosis, and Heterozygotasis, are problems that often need to be faced in marine fish farming. The most notorious parasite in seafood is Anisakis.

Anisakid nematodes found in salmon flesh | Togabi / wikimedia

Anisakis (also known as the sea stomach nematode) is a nematode parasite that is distributed globally and can be found in major oceans around the world. There are many types of marine fish infected by Anisakis, including edible fish such as salmon, king salmon, tuna, sea bass, cod, hairtail, conger eel, grouper, herring, sea bream, etc. In addition, squid, which is not a fish, is also one of the hosts of Anisakis.

If Anisakiasis enters the human body, it will cause health damage to the human body. For example, acute Anisakiasis. Acute Anisakiasis is caused by a large number of live worms entering the body. These live worms drill into human tissues, causing tissue swelling, bleeding and even inflammation , which in turn causes patients to experience symptoms such as nausea, abdominal pain and vomiting. In addition, this parasite can also cause allergic Anisakiasis . So, don't think that there is no risk of parasites when eating seafood.

How to prevent parasitic infections?

1. Do not eat freshwater aquatic products raw . Freshwater aquatic products have a much greater risk of parasites, so never eat freshwater aquatic products raw.

2. When eating out, especially seafood and meat, try to go to regular restaurants.

3. If you cook it yourself, freeze the seafood you buy at home first. Parasites are afraid of low temperatures. If you want to make sashimi at home, you might as well freeze the sashimi you buy at home for about a week before eating it.

4. Cook thoroughly before eating. Heating thoroughly is the most effective way to kill parasites. When eating seafood and other foods outside, many people choose to eat them raw for the sake of deliciousness, but the risk of parasite infection is actually very high. It is best to heat them thoroughly before eating.

5. A special reminder to everyone: soy sauce, wasabi sauce and white wine are not enough to kill these parasites , so don't be superstitious about their effects.

6. Pay attention to standard operation and keep raw and cooked food separate . When cooking seafood at home, you must pay attention to standard operation and keep raw and cooked food separate to prevent cross contamination.

7. Beware of fakes. Some businesses will use freshwater farmed rainbow trout as salmon and golden apple snails as field snails, which will increase the risk of parasite infection. It is recommended to shop at reliable shopping malls, supermarkets, and restaurants.

Author: Ruan Guangfeng

This article comes from the Species Calendar, welcome to forward

If you need to reprint, please contact [email protected]