A wriggling worm was discovered living in a young woman's tonsil just a few days after she ate sashimi.
The 25-year-old woman came to St Luke's International Hospital in Tokyo with complaints of a sore throat. Reported in the American Journal of Tropical Medicine and Hygiene, doctors peered into the patient's mouth and noticed a moving worm poking out of her left tonsil.
Once removing the invader with a pair of tweezers, the live worm was found to be 3.8 centimeters (1.5 inches) long, black in color, and cylindrical like an earthworm. Fortunately, she quickly recovered after the brief procedure and her blood tests showed no sign of any complications.
The worm in question (image below) belongs to a species known as Pseudoterranova azarasi, an uncommon parasitic nematode that lives in fish and marine mammals during certain stages of its life cycle. By no coincidence, the patient said she’d been having symptoms, namely a sore throat, for 5 days that arose shortly after she ate sashimi, a Japanese delicacy consisting of fresh raw fish or meat sliced into thin pieces.
Doctors have documented hundreds of similar cases involving similar species of Pseudoterranova worms after people have eaten raw fish. It's sometimes dubbed “tingling throat syndrome” as it causes symptoms such as a sore throat, a tingling sensation, and a cough. Eating raw fish also increases your risk of contracting tapeworm, ribbon-like worms that tend to live in your digestive tract and can cause a range of gastrointestinal symptoms, such as nausea, loss of appetite, abdominal pain, and diarrhea.
This new case study also notes that there’s been a notable increase in such cases following a rise in popularity of sashimi and sushi across the world. While not all sashimi is riddled with gross worms that can hide in your tonsils, eating raw seafood does increase one's risk of foodborne illness because cooking usually kills most would-be invaders, whether it’s bacterial, viral, or a parasite.
However, so-called “sushi-grade” fish that’s prepared raw is deeply frozen to rid the fish of any parasitic worms. Under US guidelines, this typically involves one of three processes: freezing at -20°C (-4°F) or colder for 7 days, freezing at -35°C (-31°F) or colder until solid and storing at the same temperature for 15 hours, or freezing at -35°C (-31°F) until solid and storing it at -20°C (-4°F) or below for 24 hours. Similar standards exist throughout the European Union and other parts of the world.
That said, these processes are not foolproof and are thought to be less effective for roundworms and flukes. It also doesn’t kill off bacteria that can make you sick, although it does slow its growth.
Broadly speaking, however, the risk of getting a parasite from eating raw sashimi or sushi is relatively low, especially if it’s been well-prepared at a restaurant with good health and hygiene standards.
So, nevermind the nematodes and pass the soy sauce.