That yummy fish may carry a dangerous passenger
“Freshwater salmon” farming is now trending on Chinese social media after CCTV-2 reported that over one-third of the salmon on the Chinese market comes from the Qinghai-Tibet Plateau.
“The Longyangxia Reservoir in Gonghe County, Qinghai Province has the largest salmon farm at the highest altitude in China,” CCTV Economy (@央视财经) recently posted on Weibo.
“But hatching the spawn/fry that traveled across oceans to the reservoir at an altitude of 2,600 meters was once a tricky problem.
“Now, the salmon are growing better and better on the plateau, and one-third of the salmon in the Chinese market come from this farm.”
Immediately, Weibo users started to discuss the parasite problems in “freshwater salmon.” (Technically no freshwater salmon, but in China people call it freshwater salmon because it looks like the real salmon.)
Salmon is a popular fish for sashimi.
Unlike ocean salmon, freshwater fish cannot be eaten raw.
User @難梦清明 reblogged the post and wrote:
“This means over one-third of the salmon in the Chinese market are actually freshwater fish.
“The most important problem is that the parasites in freshwater fish can complete their life cycle in the human body. There’s a severe supervision loophole.
“But instead it’s promoted as an achievement, thanks to CCTV Economy. I think I won’t touch any salmon sashimi in my lifetime.”
It was picked up by thousands of users, but the blogger later deleted the post. However, concern spread quickly and soon people started calling “freshwater salmon” “fake salmon,” “poisonous salmon” and labelled it a health hazard.
The “freshwater salmon” farmed in Qinghai is actually rainbow trout (Oncorhynchus mykiss) from the family of Salmonidae, the same as salmon (Salmo salar). But in China, both are known as sanwenyu.
The flesh of rainbow trout is very similar to salmon — bright orange with thin white strips of fat. And the taste of the raw fish is also similar.
Rainbow trout.
Huang Bing, a professor at the Shanghai Veterinary Research Institute of the Chinese Academy of Agricultural Sciences who specializes in parasitology, says that the freshwater fish farmed in lakes are indeed carrying parasites.
“In freshwater fish, some of the parasites may be infectious to humans, while some are only infecting aquatic creatures,” Huang said.
“For rainbow trout, the anisakis parasite is common and could infect people.”
And in terms of sea fish, the deep-sea species are safer than those living offshore because of the lower level of pollution from human activities.
Huang stresses that selling or marketing the rainbow trout as salmon is deceiving consumers but it doesn’t mean the fish is not edible. In fact, when fully cooked, the rainbow trout is tender, with a mild flavor.
“The authentic deep-sea salmon carries the risk of picking up parasites if the fish is contaminated during processing — such as when the same knife and cutting board are used for dealing with other ingredients,” he said.
Summer is more favorable for the development of some parasites and people also have wider selections of meat and vegetables.
“There’s just one principle to follow: Eat fully cooked meat and vegetables,” said Huang.
“It’s easy to prevent parasitic infection. Just follow all the safe handling guidelines and separate the knives and boards for raw and cooked ingredients. There’s not much to worry about.”
It is important to separate the knives and boards for raw and cooked ingredients.
Common parasites
Tapeworm is a very common parasite found in many meats, such as beef, pork, lamb and rabbit. Humans can pick up tapeworm through ingesting contaminated food or water, especially raw and undercooked meat.
The infection comes from ingesting the tapeworm’s eggs or larvae. Once the eggs are inside the intestines, they develop into larvae, which are mobile and can migrate out of the intestines and form cysts in other tissues such as the liver and lungs, Huang said.
Ingesting larvae cysts from meat would lead to the development of adult tapeworms in the intestines.
The symptoms of intestinal infection include nausea, weakness, loss of appetite, diarrhea and weight loss.
If the larvae migrate out of the intestines into other tissues, they can cause headaches and seizures.
The majority of meats like pork and lamb are served fully cooked. But raw beef and venison are sometimes made into tartar/carpaccio dishes, and steak is often eaten medium rare to rare, so using quality-assured ingredients is a must in preventing infections.
Summer is a time for eating fish, shrimp and crabs, and these present a high risk of parasitic infections if not cooked or handled properly.
Drunken shrimp and drunken crab are two staple Shanghainese dishes, soaking live river shrimp or crabs in hard liquor. As delicious as they are, these kinds of dishes can infect people with parasites very easily.
Drunken crab soaks the live crabs in liquor and is eaten raw, it can infect people with parasites very easily.
And the crowd favorite, crayfish, also carry parasites like lung fluke and liver fluke.
In addition to fully cooking freshwater crustaceans, it’s important to discard the crayfish heads, where the majority of bacteria and parasites gather.
Bullfrog is another popular delicacy and favored by many for its tender, juicy meat.
But they can carry many kinds of parasites and it’s crucial to select the artificially bred animals.
“The environment the bullfrogs live in is very important,” said Huang.
“If it’s contaminated by the faeces of parasite carriers, there’re also risks.”
Eating snake is even more dangerous, according to Huang, because they carry a large number of parasites.
Cold snake skin salad is a popular dish, but Huang suggests avoiding it because the skin is only very briefly cooked in hot water — not long enough to kill the parasites.
Apart from meat and fish, parasites are also found in vegetables, most notably the water chestnut and jiaobai (Manchurian wild rice), as aquatic plants can be contaminated by parasites in the water. “Also, don’t drink unboiled water, the common parasites include cryptosporidium and giardia, which cannot be filtered or killed by chlorine,” said Huang.
Jiaobai (left) and water chestnut (right) are vegetables that could carry parasites.
