(CNN) - A woman in Japan visited the doctor for a sore throat and was surprised with an unusual diagnosis: a worm lived inside her tonsil.
The 25-year-old woman underwent a physical examination at Tokyo's St. Luke's International Hospital after being left with a sore throat and irritation five days after eating a variety of sashimi, according to a case study published in the American Society of Tropical Medicine and Hygiene.
Doctors identified a black worm, which was 1.5 inches (3.8 centimeters) long and still moving, inside the woman's left amygdala, and removed the creature with forceps.
DNA testing on the worm identified it as a fourth-stage larva of Pseudoterranova azaras , a parasitic earthworm, the study, published in July, revealed.
The parasite infects the stomach after a host has consumed larvae in raw or undercooked marine fish, according to the study, with more than 700 cases reported in Japan, the North Pacific countries, South America and the Netherlands.
The results of the woman's blood tests were normal and her symptoms improved rapidly after the worm was removed, the newspaper noted.
Doctors and scientists have documented similar infections in patients who ate seafood dishes.
Anisakiasis, a disease caused by eating parasitically contaminated fish or shellfish, is on the rise in western countries, where sushi and other raw or undercooked seafood has gained popularity, according to a 2017 report published in BMJ Case. Reports.
In one particular case, a previously healthy 32-year-old man was found to have an inflamed intestinal membrane with a tightly attached parasite, its end penetrating the stomach, which was discovered after the patient suffered from severe pain in the upper intestine, vomiting and fever for a week. During an interview, the man said he had recently eaten sushi.
