Doctors writing in the British Medical Journal Case Reports said sushi’s growing popularity in the West could be linked to a rise in parasitic infections.

A team of doctors from Portugal raised concerns after a 32-year old man was admitted to hospital complaining of pain in his abdomen just below his ribs, vomiting and had a slight fever since the previous week.

An endoscopy revealed larvae of a worm-like parasite firmly attached to an area of swollen and inflamed gut lining. Microbiological analysis showed the larvae belong to the Anisakis spp. The worm Anisakis nematodes causes’ zoonosis Anisakiasis which invade the stomach wall or intestines of humans. It is caused by consumption of contaminated raw or undercooked fish or seafood.

Two views of the parasite, seen here firmly attached to an area of the patient’s upper gastrointestinal tract. Photograph: Carmo et al/BMJ case reports

A special kind of net was used to remove the larvae and the patient rapidly recovered.

The doctors added that most cases of anisakiasis to date had been reported in Japan but warned: “However, it has been increasing recognized in Western Countries”

EU food hygiene legislation requires fish that is to be eaten raw should be frozen before it is sold to consumers to ensure any parasite have been killed.

However, if making your own sushi from fish at home ensure that a reputable recipe is followed and the fish has been frozen for at least four days in a domestic freezer.