Doctors Found Roundworm in a Woman’s Tonsil in Japan After Eating Sashimi

Humans usually cook their food before consuming it. But some cultures eat raw meat and unknowingly also ingest the parasites that live in the flesh. For instance, the Japanese delicacy, sashimi, can infect the eater with various unpleasant aquatic parasites.

Roundworms Found at the Back of a Woman's Tonsil

Science Alert reports that the unfortunate experience of a 25-year-old woman in Japan had a particularly nasty surprise after eating sashimi. According to the case report, the woman was sent to St. Luke's International Hospital in Tokyo five days after eating sashimi and was complaining of pain and irritation in the back of her throat.

The doctors immediately conducted blood tests on her, and it went back normal. Overall, she seemed otherwise fine, but a closer inspection of her throat revealed that something was off. The doctor found something black and squirming in her left tonsil, which was extracted later by a tweezer. They have identified the wriggling culprit and put it on a petri dish.

"The worm body was black, 38 millimetres long, 1 millimetre wide, and was moulting the outer cuticle [flexible exoskeleton]," wrote the doctors in their case report. "DNA PCR and the fact that the worm was in exuviation revealed this worm was a fourth-stage larva of Pseudoterranova azarasi."

P. azarasi is a type of nematode or roundworm, and they are a known hazard of eating another Japanese food, the sushi. Infection to the throat by this parasite is rare since most of the 700 cases reported during the mid-1990s across Japan, the North Pacific countries, South America, and the Netherlands mostly occurred in the stomach.

Although these worms are a member of the Anisakidae family, the symptoms are generally not as severe as those caused by other parasites like the herring worms, in which nematode larvae attach themselves to the lining of the esophagus, stomach, and the intestine.

Since PCR is not widely available, doctors noted that it is important to be able to identify P. azarasi visually. PCR is the process of replicating the DNA to obtain a large sample used for testing.

"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," the doctors wrote in their report.

What Happened to the Patient?

Freezing the fish should kill the parasites within it. Different countries have different guidelines for regulating raw meat. However, some of them have lax guidelines or none at all, which means that it will be hard to determine whether the raw fish are safe to eat.

The good thing about throat infection is that roundworms are easily detected and easier removed than stomach infection. There is no pharmacological intervention, and the best treatment is to remove the worms from the affected area.

So, after removing the worm from the back of her tonsil, the woman was discharged from the hospital. All her symptoms cleared up quickly as soon as the procedure was done. Her experience might become a reminder to her to maybe think twice the next time she craves for a raw fish.

The doctors published their report in The American Journal of Tropical Medicine and Hygiene.