Sushi Delights and Parasites: The Risk of Fishborne and Foodborne Parasitic Zoonoses in Asia
Sushi Delights and Parasites: The Risk of Fishborne and Foodborne Parasitic Zoonoses in Asia
By Michele Barry, MD, FACP
Professor of Medicine, Co-Director, Tropical Medicine and International Travelers’ Clinic, Yale University School of Medicine
Dr. Barry is a consultant for the Ford Foundation, and receives funds from Johnson & Johnson.
Synopsis: Because of worldwide popularization of Japanese cuisine, travelers who consume sushi and sashimi in countries where certain zoonoses are endemic, and pre-freezing is an uncommon practice, may put themselves at risk for infection. Sushi and sashimi prepared without flash freezing can put the traveler at risk for exotic fishborne parasites. Undercooked wild animal meats also served as sushi and sashimi overseas can also become sources of zoonotic parasites. This review provides practical background information with an excellent table of endemic regions.
Source: Nawa Y, et al. Sushi Delights and Parasites: The Risk of Fishborne and Foodborne Parasitic Zoonoses in Asia. Clin Infect Dis. 2005;41:1297-303
A review of the potential parasites travelers might acquire by eating traditional Japanese sushi (rice with raw fish wrapped in seaweed) or sashimi (thinly sliced raw fish) was reviewed in CID by Nawa and colleagues. Due to FDA recommendations, most expensive marine fish served in US restaurants have been frozen at less than -35°C for 15 hours, or at less than -20°C for 7 days and, thus, pose a very low risk of infection. Fortunately, the commonly served tuna, yellow tail, snapper, salmon, and flatfish/flounder rarely carry parasites; other than salmon, which may harbor Diphyllobothrium latum. Cheaper marine fish such as cod, herring, mackerel, or squid could transmit Anisakis larvae. In rural areas in Japan, various other animals (crabs, snails, frog, boar, bovine liver) are consumed raw or undercooked and served as sushi or sashimi, especially in the mountainous areas. This review provides practical information regarding fishborne parasites acquired in Asia.
Anisakiasis incidence in Japan has felt to be increasingly due to enhanced detection by endoscopy. These larvae usually cause acute abdominal pain within a few minutes after consumption of infected fish to several hours after they penetrate the gastric wall. Rarely, they can penetrate the intestine and migrate to other organs. An antigen-capture ELISA with reported sensitivity and specificity of near 100%; eosinophilia and/or endoscopy can clinch the diagnosis once an immune response has developed.
Diphyllobothriasis infection is spreading in Japan due to commonly served lake trout and salmon, with > 100 cases described annually from the north. Detection of the tapeworm is usually based on ova or proglottids being found in the feces. Megaloblastic anemia is rarely seen.
Gnathostomiasis is mainly contracted by consumers of sashimi in Thailand and Japan—although a recent outbreak occurred in Latin America. Various fish harbor the parasite: tiny squid, snakehead, catfish, tilapia, brook trout, and sashimi of terrestrial snakes have been implicated. Migratory erythema, serpiginous eruptions, and dramatic eosinophilia are common symptoms. Occasionally, serious neurological illness can present as eosinophilic meningoencephalitis, radiculitis, and subarachnoidal bleeding; less commonly migration to other organs can occur.
Intestinal capillariasis is endemic in the Philippines and Thailand, but sporadic cases occur in Japan, Korea, Taiwan, India, Iran, Indonesia, and Egypt. Freshwater and brackish-water fish have been implicated, and patients will experience diarrhea and abdominal pain. Characteristic ova are passed in stool samples.
Paragonimiasis westermani causes human disease, especially in Asia, after ingestion of infected freshwater crabs. Fever, chest pain, hemoptysis, and lung lesions mimicking cavitary tuberculosis indicate disease. Ectopic migration can occur, causing extrapulmonary symptoms; cutaneous and cerebral diseases have been described. Diagnosis is confirmed by detection of ova in sputum, stool, biopsies, or serologic testing.
Several species of liver flukes, Clonorchis sinensis, and Opisthorchis viverrini are known to cause hepatobiliary disease in southeast Asia. Human infection occurs after eating raw freshwater or brackish water fish carrying infective larvae. Heavy infection can lead to jaundice, liver cirrhosis, and cholangiocarcinoma. Another important liver fluke infection caused by Fasciola hepatica can result from ingesting aquatic plants or sashimi of bovine liver—a delicacy in Yakitori bars in Japan. Intestinal flukes (Metagonimus yokogawi) are a well-known sequelae of eating the famous freshwater fish Ayu in Japan. Eating raw snails, slugs, or green salads may precipitate angiostrongyliasis—a cause of eosinophilic meningitis.
Sparganosis or spirometrosis occurs when sashimi of infected frogs or snakes are ingested. Approximately 500 cases have been reported in Japan. Larvae usually appear in the subcutaneous tissues as slow-growing migratory nodular lesions. Occasional CNS lesions occur. Table 1 in the paper outlines those areas with parasite endemicity.
A review of the potential parasites travelers might acquire by eating traditional Japanese sushi (rice with raw fish wrapped in seaweed) or sashimi (thinly sliced raw fish) was reviewed in CID by Nawa and colleagues.Subscribe Now for Access
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