A Japanese woman started experiencing sore throat symptoms after eating assorted sashimi and found a worm burrowing in her tonsils. The 25-year-old woman had been suffering through throat pain and irritation for five days when she finally sought medical help at St. Luke's International Hospital in Tokyo.

Following a physical examination and upon having a closer look, the doctors were quick to identify the cause of the woman's problem. Actively wriggling on the surface of her left tonsil was a black worm. It was identified as a nematode roundworm measuring 38mm long and 1mm wide. It was removed with a pair of tweezers after which the patient's symptoms immediately improved.

Nematode worms ( Pseudoterranova Azarasi ) are parasites that typically affect people who eat raw fish. It will infect a person's stomach after the host consumes larvae from raw or under-cooked fish. There are more than 700 cases recorded across countries where people enjoy raw fish dishes such as Japan, South America, the Netherlands and North Pacific countries.

According to the study published by the American Journal of Tropical Medicine and Hygiene, at the time the worm was extracted, the larvae was already in the fourth stage of its growth cycle where it was starting to molt and shed off its outer cuticle.

In some cases, people report a tingling throat sensation that leads to coughing and retching. Some have even coughed up the worms without any further health issues. Cases of this parasite infection known as Anisakiasis have started to increase in many western countries due to the rising popularity of sushi and other raw seafood dishes such as ceviche and tuna tartare .

One other case was of a 32-year-old man who complained of severe upper stomach pain, vomiting and fever that lasted for a week. Doctors' findings showed a swollen intestinal membrane that had the same parasite attached to it, with its tail end penetrating the stomach lining. The man said he had eaten sushi before experiencing the symptoms.

Although these parasite infections seem alarming for sushi loving foodies, it is important to note that most of these infections occur from home and not from restaurants, as professional chefs are highly trained to prepare these dishes.

sushi worm
In another case, a 32-year-old who had eaten sushi was found with a parasite, pictured right, burying into his gut lining Reuters/Dr Joana Carmo