688 metacercariae were found on a water chestnut. How can we eat water chestnuts, water caltrops and wild rice stems safely?

Summer is the season when aquatic vegetables such as water chestnuts are on the market. I believe many of my friends are already gearing up to enjoy them.

Water Chestnut

Source: Serious Eats

However, although eating water chestnuts raw can cool you down and relieve heat, there is a risk of parasitic infection.

What is going on here? Today, I will talk to you about the issue of "insects entering through the mouth".

01

Why does eating water chestnuts raw lead to parasite infection?

Compared with the "famous" parasites such as Ascaris lumbricoides and Schistosoma japonicum, the ginger worm can be regarded as an unknown "eighteen-line" small worm. Many people even heard of this name for the first time.

So, what kind of parasite is the ginger worm?

Fasciolopsis buski, also known as Fasciolopsis buski (Lankester, 1857) Odhner, 1902, is a large trematode of the order Digenea, class Trematoda, family Fasciola that can parasitize the small intestine of humans and pigs . Since Fasciolopsis disease is mainly prevalent in Asia, it is also called the Asian large intestinal fluke.

Source: Human Parasitology, Ninth Edition

The ginger worm is named for its shape resembling ginger slices. The adult is an oblong flat piece, flesh-red in color, 20-75 mm long, 8-20 mm wide, 0.5-3 mm thick, and has abundant and thick muscles. The ginger worm's eggs are 130-140 μm long and 80-85 μm wide, making them the largest worm eggs among human parasites.

Source: Human Parasitology, Ninth Edition

Humans and pigs (including wild boars) are the definitive hosts of the ginger worm. The adult ginger worm parasitizes the upper small intestine of the definitive host . After laying eggs, the eggs are discharged into the water with feces. Under suitable temperature conditions, they can hatch into miracidia after 3 to 7 weeks. Subsequently, the miracidia enter the intermediate host, the flat spiral snail, and develop into cercariae after 1 to 2 months. After that, they escape from the intermediate host and attach to the surface of aquatic plants, such as water chestnuts and other transmission media. The cercariae will shed their tails at this stage to form metacercariae. Metacercariae attach to food and enter the host's body, attach to the mucosa of the upper small intestine to absorb nutrients, and develop into adults.

The pathogenic mechanism of the ginger worm parasitizing the human body mainly includes mechanical damage and hypersensitivity reactions caused by the absorption of the worm's metabolites by the human body.

The ginger worm is huge in size and is the largest trematode that parasitizes the human body. Its sucker has well-developed muscles and strong adsorption ability, which can cause necrosis and shedding of the host's intestinal mucosa, causing inflammation, bleeding, and edema. In severe cases, it can even develop into ulcers or abscesses.

The metabolites of the worm may trigger an abnormal and excessive immune response in the host, i.e. a hypersensitivity reaction, which is mainly manifested by the infiltration of neutrophils, lymphocytes and eosinophils in the lesion area. In severe cases, it may cause abdominal pain, abnormal defecation and malnutrition, and even intestinal obstruction. Children infected with the ginger worm often develop low fever, edema, ascites, malnutrition, intellectual impairment and developmental disorders, and in severe cases may even die from organ failure.

Not only that, in rare cases, the ginger worm will also parasitize ectopically in the bile duct, causing patients to experience repeated symptoms such as abdominal pain, bloating and fever.

In addition to the water chestnuts mentioned above , water chestnuts, wild rice stems, lotus roots and other aquatic vegetables commonly seen on the table are common "gathering places" for the metacercariae of the ginger worm . There was a report that 688 metacercariae were found on a water chestnut. Not only does eating these aquatic plants raw increase the risk of infection, but drinking raw water during the season of high infection incidence also poses a certain risk of infection.

02

How to prevent ginger locusts

I just wanted to stay cool, but I didn't expect to take such a big risk. So how can I avoid the "bug crisis" in summer?

Source: Greenish Thumb

Although metacercariae have a certain resistance and can survive on wet paper for more than 10 days at 28-30°C and for a year at 5°C, they are not resistant to high heat and dryness and can be killed by boiling in water for 1 minute or exposing in the sun for 1 day. Therefore, the key measure to avoid "worms entering the body through the mouth" is to avoid eating raw water fruits and vegetables such as water chestnuts and water caltrops. Wash the ingredients carefully and cook them thoroughly, and they can be eaten safely. Secondly, not drinking raw water from rivers and ponds and avoiding feeding pigs with feed contaminated with metacercariae can help us prevent ginger worm infection.

In addition, strengthening public health management, improving the feces treatment process, and preventing human and pig feces from contaminating water bodies and causing the spread of infection are also important auxiliary means to prevent ginger worm infection.

Once you discover that you may have parasites in your body, you must go to the hospital in time and take medicine as prescribed by the doctor to avoid delaying the disease and causing serious consequences.

Although infection with parasites is only a probabilistic event, some of our friends have been eating raw water chestnuts since childhood and are still safe and sound; some people were unfortunately infected after trying it only once.

But Tadpole still wants to remind everyone that it is not worthwhile to put yourself at high risk of parasitic infection for the sake of temporary coolness and refreshment. It is better for everyone to find a safe and reliable way to cool down in summer!

END

Audit expert: Wang Guoyi, Postdoctoral Fellow in Food Safety

Tadpole Musical Notation original article, please indicate the source when reprinting

Editor/Xiao Xitushuo