A man vomited for more than a year and had a craniotomy to remove parasites. The cause turned out to be this kind of hot pot that everyone eats

Speaking of bullfrog, it is a favorite on many people's tables. The tender and juicy frog meat is mouth-watering whether it is stir-fried, braised or hot pot. But have you ever thought that behind this delicious bullfrog may be an "invisible killer" - parasites!

Image source: Screenshot of social platform

Recently, there was a shocking case on the Internet: a netizen vomited for more than a year and finally had to undergo a craniotomy. It turned out that the culprit was actually parasites! He had eaten bullfrog hot pot before. Does this sound a bit creepy? How can bullfrogs have parasites? How to prevent parasitic infections?

What are the parasites in bullfrogs?

Bullfrogs have delicious meat and are loved by many people. However, bullfrogs may also carry parasites - sparganosis.

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

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 people eat infected tadpoles or frogs, the larvae will enter our bodies.

The life cycle of Spirochete mansoni. Image: Human Parasitology/People's Medical Publishing House

Although humans are not the final host of Spirometra, the sparganum will not stay still in the human body. It will run around in different parts of the human body, causing various injuries to the body, and the damage may be all over the body. The 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. What's more terrifying is that sparganosis can also invade the brain, and in severe cases it may cause paralysis.

What are the routes of infection?

There are many ways to get infected with sparganosis. For example, some people like to eat frogs and snakes, but they handle them improperly, such as eating frogs or snake tissues that have not been processed in any way - drinking snake blood, swallowing snake gall, eating cold snake skin, or accidentally drinking water contaminated by worm-carrying sword water fleas, which may cause sparganosis infection.

Some people also have a "strange" eating habit of eating tadpoles raw, which can easily lead to infection. You should know that the claim that eating tadpoles raw can cure diseases is completely nonsense, and it can cause people to be infected with parasites.

In addition to eating, applying it 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 is said to have the effect of "cooling and detoxifying", many people apply raw frog meat on wounds or skin abscesses, which can also cause infection.

How to prevent parasitic infections?

1. Choose the right bullfrog

Don't buy wild bullfrogs just because they are cheap, as they are the "base camp" of parasites. Wild bullfrogs are very likely to carry sparganosis. A study analyzed the infection of sparganosis in frogs sold in Guangzhou. The results showed that the infection rate of wild frogs was as high as 51.92% (216/416), while the infection rate of farmed frogs was 0 (0/1382); random inspections in Shanghai, Taiyuan and other places also found that the infection rate of sparganosis in farmed frogs, including bullfrogs, was very low, and the random inspection results were all 0.

Artificially bred bullfrogs have a controlled environment and a much lower risk of parasites. Be sure to buy artificially bred bullfrogs from formal channels. Safety first!

2. Cook bullfrog

Sparganum can be killed in 5 minutes at 56°C. Therefore, when cooking bullfrog, make sure the core temperature of the frog meat reaches above 70°C and keep heating for at least 5 minutes. Stir-frying and hot pot cooking methods may not cook the ingredients thoroughly, which can easily leave hidden dangers of parasites.

3. Don’t eat freshwater seafood raw

Freshwater aquatic products have a high risk of parasites, especially wild ones. Don't try to eat them raw, pickled, or as sashimi. Safety is everything.

4. Standardized processing

The chance of farmed bullfrogs carrying sparganosis is very small, and the risk of parasite infection is very low, but this does not mean that you can eat them at will.

From the perspective of food safety risk control, only by cooking thoroughly can the sparganosis be killed. When making bullfrogs yourself, be sure to separate raw and cooked food. Use special knives and cutting boards to handle raw meat to prevent cross contamination. If there are wounds on your hands, it is best to wear gloves when handling them to prevent parasites from drilling into the skin.

5. Freezing to kill insects

In addition to heat treatment, freezing can also kill parasites. Freezing bullfrog meat at -20°C for more than 24 hours can effectively kill sparganosis.

6. Don’t be superstitious about “sterilization artifacts”

I would like to remind everyone that soy sauce, wasabi sauce and white wine are not enough to kill these parasites, so don't be superstitious about their effects.

In short, although bullfrog is delicious, you must be careful when eating it. As long as you follow the above points, you can enjoy the food without worry!

References

[1] Lin Ximeng, Wang Zhongquan. Overview of clinical characteristics of sparganosis in my country[J]. Chinese Journal of Pathogenic Biology, 2011, 6(06): 467-468+471. DOI: 10.13350/j.cjpb.2011.06.022.

[2] Zhang Kairen, Wang Rui, Gu Guanjun, et al. Survey on infection of Sparganosis mansoni in Xiangxi Autonomous Prefecture from 2010 to 2018[J]. Tropical Diseases and Parasitology, 2021, 19(2):82.

[3] Feng Jieping, Hong Qing, Liu Haijuan, et al. Investigation on infection and source of sparganosis in frogs sold in Guangzhou[J]. Chinese Journal of Zoonoses, 2015, 31(01): 88-91.

[4] Lu Lu, Jiang Shoufu, He Yanyan, et al. Investigation of parasitic infections in animal food sold in Huangpu District, Shanghai, 2015-2017[J]. Tropical Diseases and Parasitology, 2018, 16(01): 23-25.

[5] Li Ke, Li Dan, Fan Wenjia, et al. Infection status of Sparganosis mansoni in frogs sold in Taiyuan and residents’ awareness of Sparganosis mansoni[J]. Journal of Shanxi Medical University, 2018, 49(11): 1316-1318. DOI: 10.13753/j.issn.1007-6611.2018.11.008.

[6] Tang Guiwen, Chen Yan. Effects of different physical and chemical factors on the infectivity of Sparganum mansoni[J]. Chinese Journal of Parasitology and Parasitic Diseases, 2011, 29(5): 368-371.

Planning and production

Author: Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center

Review丨Zhang Yu, researcher/PhD, Chinese Center for Disease Control and Prevention, national health science expert