Stomach worms from raw fish bought in Calgary believed to be 1st of its kind in Canada

Calgary doctors say they've treated what's believed to be the first case of stomach worms resulting from the eating of raw fish purchased at a Canadian grocery store.

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Dr.Stephen Vaughan, who works out of the South Health Campusin Calgary, reports the findings as lead authorofa "clinical vignette" in the Canadian Journal of Infectious Diseases and Medical Microbiology.

The report says a50-year-old man arrived at the emergency department complaining of vomiting and severestomach pain, one hour after eating raw salmon.

"He made his own sushi at home and obviously it wasn't prepared properly,"Vaughan tells CBC News.

The fish the man purchased was not sushi-grade, a process that eliminates parasites through freezing and cold storage.

"Within six hours after eating it he developed severe, intense abdominal pain, some of the worst that he could describe."

As time went on,the man developed a fever of 39C and continued to experience severe abdominal pain.

After running numerous tests, doctors eventually diagnosed the problem by sending a small camera down the man's throat and spotting the worms at the centre of small ulcers in his stomach.

The Homestretch6:55Homemade sushi leads to stomach worms

It all started when an Alberta man decided to buy some raw salmon to make his own sushi at home. He wound up in hospital with worms eating through his stomach lining. Dr. Stephen Vaughan is an infectious disease specialist at the U of C's medical school.

Some of the worms were removed and identified as anisakis, a type of parasite that lives in fish and aquatic mammals and leads to a condition known as anisakiasis.

1st case of its kind

"To our knowledge, this is the first case of anisakiasis acquired from raw 'wild salmon' purchased from a Canadian supermarket," the doctors wrote in their report.

"Humans become infected by eating raw seafood in dishes such as sushi, sashimi, ceviche, lomilomi, or other undercooked fish and squid dishes," the report said.

"Although a skilled sushi chef will recognize the distinctive 'watch coil' appearance of the larval worms (approximately one centimetreto twocentimetres) in raw fish, individuals preparing their own sushi may not, and may, inadvertently, become infected after ingestion of the larval nematodes."

Freeze your fish

To prevent the parasitic infection, amateur sushi chefs areadvised tofreeze raw fish for seven days at 20C,or at a lower temperature for a shorter period of time.

The doctors note that sushi prepared in Canadian restaurants and supermarkets is "very unlikely" to spread parasites because it is typically flash-frozento 35 C for at least 15 hours.

Vaughan says the risk, which exists only in wild salmon, is relatively low.

He says while some surveys have suggested up to 20 per cent of wild salmon can be infected in certain areas, he would speculate the risk of buying one from a grocery store ismuch lower, in the one to five per cent range.

"Increasing reports of acute anisakiasis will likely occur in the next few decades given the growing consumption of sushi and sashimi worldwide," the doctors conclude in the report.

Vaughan says his patient had no lasting effects.

"He had almost immediate relief of the pain after extraction of the worms and he has been perfectly fine since that time."

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