The growing popularity of sushi could fuel a rise in deadly parasitic worm infections, doctors have warned.
Raw fish can carry tiny worms that bury into the human gut if eaten, a condition known as anisakiasis, which can cause severe stomach pain, vomiting and fever.
However, in severe cases it can cause an anaphylactic reaction, with the parasites triggering an erratic heartbeat and respiratory failure, which can be fatal.
Until recently, cases in Western countries were rare because most dietary fish is cooked, which kills the worms. But the rise of sushi has led to cases in hospitals across Europe.
In the latest incident a 32-year-old Portuguese man was left in agony for a week after eating slices of raw fish from a Japanese restaurant.
When doctors put an endoscope – a long tube with a camera – down his throat they found a mass of writhing white larvae burrowing into his gut lining. After the worms were cleared out using a special kind of retrieval net, the man’s symptoms quickly cleared up.
Writing in BMJ Case Reports, the Lisbon doctors who treated him warned clinicians to consider the condition in patients with pain, nausea, vomiting and other complications, such as bowel obstruction and bleeding, who have recently eaten sushi.
Dr Joana Carmo, a gastroenterologist at the Hospital of Egas Moniz in Lisbon, said:
“Owing to changes in food habits, anisakiasis is a growing disease in Western countries, which should be suspected in patients with a history of ingestion of raw or uncooked fish.
Most people believe sushi is a nutritious, low calorie meal, but previous research has suggested it could actually be bad for you.
One study revealed that people who regularly eat sushi could be at an increased risk of heart disease.
Recent research also found that eating a lot of sushi puts people in danger of exposure to dangerous levels of mercury, which can cause heart disease, problems with brain and nervous system development, and decreased cognitive performance.
The sushi retail market alone is now worth about £68 million in the UK.