They said that consumers should be aware that while larvae for the parasitic worm Anisakis cannot survive in a human host, the ingested larvae could produce severe intestinal problems warranting a visit to the emergency room.
According to them, ingested larvae attach themselves to the tissues lining the stomach and intestines, resulting in sudden abdominal pain, nausea, vomiting, and diarrhoea.
As the larvae cannot survive in humans and eventually die, intestinal anisakiasis usually resolves on its own, say the researchers.
The two cases examined in Japan pertained to an obstruction of the small intestine. In each case, both patients, aged 64 and 70, were rushed to the emergency room with sudden abdominal pain and vomiting after eating raw sardines as sashimi two days earlier.
While anisakiasis in the stomach can be easily diagnosed by endoscopy, it is very difficult to diagnose small intestinal ansakiasis.
Upon using a multidetector-row computed tomography (MDCT), the doctors examining the two Japanese cases obtained high quality images of the small bowel, and found the intestinal blockage was caused by the presence of Anisakis larvae.
They said that fluid replacement and resting immediately relieved the patients' symptoms.
Since the symptoms of anisakiasis can mimic other gastrointestinal diseases, it might potentially be misdiagnosed as appendicitis, acute abdomen (peritonitis) or stomach ulcers.
"Anisakiasis should be considered in the differential diagnosis of small intestinal obstruction," said Dr. Mashahiro Matshushita of Haibara General Hospital