Moving Black Worm Discovered in Woman's Tonsils After Eating Raw Fish

A woman in Japan was found to have a moving black worm living in her left tonsil after she had eaten contaminated sashimi.

The worm, Pseudoterranova azarasi, is a type of parasitic worm that normally uses marine mammals such as walruses and seals as hosts. It can, however, be acquired by humans through the consumption of raw fish or squid. It is a rarely reported member of the Anisakidae family, which are intestinal roundworms that can cause anisakiasis—an infection of the gastrointestinal tract.

In a case study published in The American Journal of Tropical Medicine and Hygiene, Sho Fukui and colleagues from St. Luke's International Hospital, Tokyo, Japan, reported a rare case of the worm being found in a woman's throat.

The 25-year-old had arrived in hospital complaining of pain and irritation on the left side of her throat for five days. Her blood tests were normal. After examining her, however, the team discovered a "black moving worm" in the left tonsil. They removed it with a pair of tweezers and her symptoms quickly improved.

The worm was 1.5 inches long and 0.04 inches wide. It was in the process of shedding the outer cuticular layer of its body. Further analysis revealed the creature was Pseudoterranova azarasi in the fourth stage of larvae development.

In the report, the team says that like other parasitic worms, this species tends to infect the stomach when ingested as a third-stage larvae. They said there are fewer than 700 cases of this type of worm found in humans in Japan, the Netherlands, South America and North Pacific countries.

They said there is "limited evidence" for pharmacological treatments of the species, and that "direct removal is the most effective."

"Although oropharyngeal infection is rare, this infection is known to cause 'tingling throat syndrome' and cough and should be considered a differential diagnosis of oropharyngeal parasitosis as consuming raw fish, including sushi and sashimi, has become more popular and the number of reported cases has markedly increased worldwide," they wrote.

For gastric cases of anisakiasis, the U.S. Centers for Disease Control and Prevention says treatment normally involves removal of the worm using an endoscope. Some of the symptoms of anisakiasis include abdominal pain, nausea, vomiting, diarrhea and a mild fever.

Normally, freezing raw fish before consumption will kill off any parasites in the meat. According to the U.S. Food and Drugs Administration, freezing and storing fish at minus four degrees Fahrenheit for seven days is normally long enough to kill parasites.

Stock image of sashimi. A woman in Japan was found to have a parasitic worm in her throat after eating raw fish. iStock