Reporters learned from the First Affiliated Hospital of Sun Yat-sen University that after a family of five from Guangzhou, surnamed Yang, were all infected with Angiostrongyliasis cantonensis, another citizen was found to be suspected of being simultaneously infected with Angiostrongyliasis cantonensis and clonorchiasis due to long-term consumption of raw fish. Doctors pointed out that in addition to freshwater fish, apple snails, and东风螺 (east wind snails), deep-sea fish cannot be ruled out as a risk for parasites, and it is recommended that people in Guangzhou change their dietary habits of loving to eat raw or undercooked food.
Professor Zhan Ximei from the Department of Parasitology, Zhongshan School of Medicine, Sun Yat-sen University, pointed out in an interview with reporters that recent surveys on东风螺 (east wind snails) found that the infection rate of Angiostrongyliasis cantonensis was as high as 27%, with one snail carrying up to 622 Angiostrongyliasis cantonensis parasites. Both eating raw snails and contact with snail bodies can lead to infection, so it is not ruled out that an outbreak of Angiostrongyliasis cantonensis could occur in Guangzhou.
Eating raw东风螺 (east wind snails), apple snails, and freshwater fish all carries the risk of parasitic diseases, and eating raw deep-sea fish is not necessarily safe either. According to data from the Disease Prevention and Control Office of the Guangdong Provincial Health Department, between 1990 and 2004, about 5 million residents in Guangdong were infected with clonorchiasis. Zhan Ximei pointed out that in recent years, salmon, which has been widely accepted by Guangzhou citizens, is easily infected with "Anisakis simplex," which is prevalent in 27 countries including Japan, South Korea, and France, with Japan alone reporting over 30,000 cases.
Dr. Wang Jinhui from the First Affiliated Hospital of Sun Yat-sen University pointed out that among the cirrhosis patients of Guangdong origin seen in clinical practice, the proportion of cirrhosis caused by clonorchiasis is on the rise, which is related to the preference of Guangdong people for undercooked and raw food. It has now been confirmed that different parasites are carried in snails, freshwater fish and shrimp, deep-sea fish, and mountain delicacies, and none of them should be eaten raw in principle. Some citizens think that occasional consumption is not a big risk, but in fact, it is possible to "get infected" even after eating just once. Link for reading: Diagnosis and Treatment of Anisakiasis
Anisakis is a type of nematode whose adult parasites reside in marine mammals and whose larvae parasitize certain marine fish.
It belongs to the order Ascaridida and family Anisakidae. The main species that can cause human anisakiasis are from 5 genera: Anisakis, Pseudoterranova, Contracaecum, Hysterothylacium, and Thynnascaris.
The species reported in China are mainly from the genera Anisakis and Thynnascaris. Humans are not suitable hosts for Anisakis, but the larvae can parasitize various parts of the human digestive tract and can also cause visceral larva migrans. Human infection is mainly caused by consuming marine fish and marine mollusks containing live Anisakis larvae. The parasites mainly inhabit the gastrointestinal wall, and patients develop the disease abruptly, resembling a surgical acute abdomen, often leading to clinical misdiagnosis. This is mainly because residents in these countries like to eat pickled marine fish, or enjoy raw marine fish slices, fish liver, roe, or squid as side dishes with wine, from which they get infected, making this disease a natural focus of infection in the ocean. In China, although no cases have been reported so far, the infection rate of Anisakis larvae in the muscle or organ tissues of small fish such as mackerel, yellow croaker, and hairtail sold in domestic markets is as high as 100%, with an infection intensity of up to 401 larvae per fish; among 30 species of fish and 2 species of mollusks obtained from the East China Sea and the Yellow Sea, an 84% rate of larvae was found. This shows that the potential risk of human infection with anisakiasis in China is very high.
[Route and Mode of Infection]
Infection route: Ingesting Anisakis larvae orally.
Infection mode: Infection is caused by eating raw or undercooked marine fish (such as mackerel, yellow croaker, hairtail, etc.) and marine mollusks (such as cuttlefish) containing live Anisakis larvae. For example, eating pickled marine fish, or eating raw marine fish slices, fish liver, roe, or squid as side dishes with wine can lead to infection.
[Diagnosis]
The parasites mainly inhabit the gastrointestinal wall, and patients develop the disease abruptly, resembling a surgical acute abdomen, often leading to clinical misdiagnosis. The diagnosis of this disease is based on the detection of larvae from the stomach. The parasites are mostly found on the greater curvature of the stomach. Using the secretions and excretions of larvae cultured in vitro to detect specific antibodies in the patient's serum is an important auxiliary diagnostic method for this disease.
[Pathogenesis]
Humans are not suitable hosts for Anisakis, but the larvae can parasitize various parts of the human digestive tract and can also cause visceral larva migrans. After human infection with this parasite, mild cases may only have gastrointestinal discomfort, while severe cases manifest as sudden severe upper abdominal pain accompanied by nausea, vomiting, diarrhea, and other symptoms a few hours after eating. Fiberoptic gastroscopy may show edema, bleeding, erosion, and ulcers of the gastric mucosa. In advanced patients, tumor-like masses may be seen on the gastrointestinal wall. The pathological characteristics are abscesses or tumor-like masses centered on the submucosa with a large number of eosinophilic infiltrations, and fragments of the parasite, cuticle, or intestine can be seen inside the mass. In addition to the gastrointestinal tract, the parasite can form masses in the abdominal cavity, urinary system, subcutaneous tissue, and other places.
[Treatment]
Currently, there is no specific drug for treating gastrointestinal anisakiasis, so a fiberoptic gastroscopy can be used to remove the parasites.