When I was a child, my family often went to the pond to touch the snails, and along the shore of the pond, I could catch a few at a time. When I got enough plates, I went back to my home to soak them in clean water so that they could vomit up all the dirty things. But there were some doubts at that time, because my parents always asked me not to catch any big snails, as long as those small snails were thought to be just big snails, but I didn't know that big snails were snails because I read some related contents recently.

1, what happens when you eat snails?

Pomacea canaliculata, also known as apple snail, originated in South America and is now an invasive species in China, which will have a great impact on rice in particular. Pomacea canaliculata was first introduced as a high-protein food. However, Pomacea canaliculata contains a large number of parasites. If it is not cooked, it will cause parasitic diseases. Therefore, the snail itself is not poisonous and can be eaten, but there are still a lot of parasites, so it is best not to eat it.

When did Pomacea canaliculata appear on the dining table? Take Beijing as an example, as the weather vane of Beijing's food popularity, around 2000, three kinds of things caught fire in Guijie, namely spicy crab, crayfish and snail, and soon the whole capital began to eat them.

In 2006, an incident of Ampullaria gigas broke out in Beijing, and dozens of people were infected with Angiostrongylus cantonensis because of eating Ampullaria gigas in the romance of Shu, which seriously damaged their brains. Due to the onset of the disease 1 to 2 months after eating, many consumers lost invoices, receipts and other documents, and finally did not get due compensation.

In the natural state, frogs, snails, fish and shrimp are common intermediate hosts of parasites. For example, snails are the hosts of schistosomiasis. Therefore, it is normal for snails to carry parasitic eggs. Kai Zhong said, however, the vitality of parasites is very limited. They are afraid of cold, and even more afraid of heat. As long as they are fully heated, there are no parasites that can't be killed, including eggs.

In the five points of food safety recommended by the World Health Organization, it is emphasized that food should be cooked thoroughly, that is, the temperature in the food center should reach 70 degrees. At this temperature, protein will denature and solidify, and parasites will naturally die.

However, unlike other fish and shrimp aquatic products, the special structure of Ampullaria canaliculata may make it more dangerous.

The snail shell is hard and thick, and the screw mouth has a hard horny cover, so it is difficult for soup to enter the snail meat. The spiral structure in the screw is like a maze, which is not conducive to heat conduction. It was originally relatively large, and it was not easy to burn through. Therefore, the snail is not inedible, but needs to be burned for a while. Kai Zhong said.

He pointed out that the meat quality of Ampullaria gigas is relatively old, and if it is cooked for too long, it is very difficult to chew, which also causes restaurants to tend to shorten the cooking time.

In addition, it is also very important to separate raw food from cooked food. For example, using knives, chopping boards and containers may cause parasites to pollute cold dishes or cooked food.

According to Kai Zhong, in the 1980s or so, Ampullaria canaliculata was introduced into China from South America, initially as aquaculture, but also as feed for other aquatic products. However, it is too fertile and lacks natural enemies, resulting in flooding and eating rice roots in rice fields, resulting in reduced production. It has also done great damage to the ecology and has become an out-and-out invasive species.

In 2003, the State Environmental Protection Administration listed Pomacea canaliculata on the blacklist of the first invasive alien species in China. The reproductive ability of Ampullaria canaliculata is amazing. It can reproduce two generations a year, laying thousands of eggs at a time. A female snail can reproduce 320,000 offspring after two generations a year, which is extremely harmful. In recent years, snail disasters have occurred repeatedly in Hunan, Guangxi, Fujian and other places, which has brought great troubles to agricultural production and farmers' lives.

2. Distinguish Ampulla canaliculata from Ampulla canaliculata

Pomaceacanaliculata is aquatic, with a yellowish brown or dark brown shell and a smooth surface. The body of the snail is right-handed, approximately disc-shaped, with 5-6 layers, the body of the snail (that is,1~ 2 layers near the mouth of the snail shell) is enlarged, and the mouth of the snail shell has a cover (that is, the cover). Oviposition (that is, laying eggs). Eggs are pink when they are first laid, and they are attached to solids above the water surface in blocks.

China round snail (Gray) is aquatic. The shell surface of the snail is yellowish brown, and its shape is wide conical, with fine and obvious growth lines. There are 6-7 layers of snail, all of which are convex. The height and width of each snail increase rapidly, and the top of the shell is sharp. The height of the spiral part is greater than the height of the shell opening, and the spiral layer of the body expands. There is a shell at the mouth of the snail. Viviparous (that is, its eggs don't come out directly like snails, but stay in the mother's body to develop into young snails and then be born).

1, the shell color of Ampullaria gigas is yellow, while the shell color of Ampullaria gigas is bluish brown.

2. The vertebral tail of Ampullaria canaliculata is flat and short, while that of Ampullaria canaliculata is long and sharp.

3. The snail cover of Ampullaria gigas is flat, while the snail cover of Ampullaria gigas is round.

4. The flesh of Amphibia canaliculata is lighter in color, mostly yellow and white, while the flesh of Oncomelania canaliculata is mostly bluish brown.

3. About Angiostrongylus cantonensis

For eating snail meat, the most famous parasite is Angiostrongylus cantonensis. If you are old enough to understand the news in 2006, you should have a little impression of the sensational Beijing snail incident. In June of that year, an outbreak of Angiostrongylus cantonensis broke out in Beijing, which was caused by a group of diners eating immature snail dishes in a restaurant. At that time, Beijing Friendship Hospital admitted 8/kloc-0 patients with Angiostrongylus cantonensis, but fortunately no one died in the end. However, the central nervous system of 25 critically ill patients was seriously damaged, and the recovery period was long. Three months after their discharge, there were still 12 patients with sequelae, and even severe symptoms of visual field defect [1].

According to the literature, Angiostrongyliasis cantonensis/kloc-0 was first discovered in Guangzhou domestic mice in 1935, and the first case of disease in human body was discovered in 1945. Up to now, most cases are infected by food. Up to 2007, there were as many as 78 species of molluscs (snails and snails, slugs are molluscs) that can be parasitized by Angiostrongylus cantonensis, including Pomaceacanaliculata, China round snail (Gray) and China round snail (Cipangopaludinacahayensis). In addition, other host animals include rats, freshwater shrimps, frogs, toads, snakes and so on.

Angiostrongylus cantonensis is a kind of nematode, its adult length can exceed 4 cm, but its maximum diameter will not exceed 0.5 mm, and the diameter of larvae is counted in microns [4]. So don't think that washing snails without sand and dirt is clean, because Angiostrongylus cantonensis is invisible to the naked eye.