By: Pooja Sharma

Sushi is a traditional Japanese dish made up of small rolls of vinegar-flavored rice garnished with raw seafood, eggs, or vegetables. Eating Sushi has been on the rise in Western countries and the consumption has grown more than ever in the past decade itself. Sushi is actually considered an American meal now with annual Sushi Industry Revenue in the US rising to a whopping 2.25 billion dollars.(1) However, this special ‘wine and dine’ full of heart healthy Omega Fatty Acids is also associated with the risk of various foodborne illness and diseases that can be caused by raw seafood present in it.

A Parasitic Infection from Sushi?

First among them is Anisakiasis. Anisakiasis is spread by Anisakis, a parasite which enters the human intestinal system after consumption of under processed fish. Once this worm enters the human body, it tries to penetrate the intestinal walls to survive. This survival process can last for up to weeks before the worm eventually dies leaving an inflamed mass. This signals the production of immune cells in the body which surrounds the parasite, and hence, blocks the digestive tract.

Once the worm enters the human body, it can cause a havoc – resulting in symptoms such as: abdominal pain, nausea, vomiting, diarrhea, mild blood in mucus and stool and fever. In rare conditions, it can also cause digestive bleeding and inflammation of the inner wall of the abdomen. This type of infection doesn’t usually require any diagnosis, and the immune system response throws out the infection by vomiting or coughing. In some cases, diagnosis may be needed and the worm is removed by endoscopy, radiography, biopsy, or surgery.

In rare cases, Anisakiasis can cause allergic reactions in the body causing skin rash, swelling, and even anaphylaxis. This allergic reaction can also occur without the symptoms mentioned above, making it difficult for the doctors to find out the cause. These allergic responses can be life threatening. Occupational Allergy like asthma, conjunctivitis etc. has been observed in various fish processing workers.

Anisakiasis can infect salmon, cod, herring, mackerel, halibut, squid, and red snapper.

But that’s Not All…

Second illness associated with eating Sushi is Diphyllobothriasis, another intestinal infection caused by a fish tapeworm, D.Latum. Salmon is the most important intermediate host of D.Latum. But it can also infect trout, pike, and sea bass. It is generally spread by fish that has not been frozen to a proper temperature.

Infection can reduce levels of B12 in the body and could also lead to anemia. Other symptoms include diarrhea, abdominal pain, chronic hunger or appetite, fatigue, unintended weight loss, and weakness. Your doctor might order a blood test in order to check whether there is any sign of worm, parasites or eggs in a person’s stool. Treatment generally involves medication which can cause spasms in the worm’s muscles and kill it. Once the worm is dead it can pass out in human stool.

The third most common illness associated with raw seafood present in Sushi is Vibriosis. There are various types of Vibrio Species which can infect the human body but the two of the most commonly responsible for maximum US illnesses include Vibrio parahaemolyticus (found in under processed fish and shellfish) and Vibrio Vulnificus (found in shellfish especially oysters, clams, and crabs). Most infections occur between May and October when the water temperature is warmer and there is a higher concentration of the Vibrio Species breeding in the water.

Symptoms associated with infection are vomiting, diarrhea and stomach cramps. In healthy people, the infection doesn’t pose a severe health risk but in people with weakened immune system or any liver disease, the microbe can enter the bloodstream and cause a life-threatening condition. On rare occasions, the Vibrio can also infect human body when a wound is exposed to brackish or salt water.

People with mild cases of Vibriosis can recover within a few days but those infected severely might need intensive care.

There’s More!

Other infections associated with Sushi include:

  • Mercury Poisoning: Predator fish, like shark, swordfish, catfish, king mackerel, etc. are more prone to high levels of mercury of present in their body than other fish. Still, consuming fish more often can increase your chances of MethylMercury Poisoning. Fish low in Mercury include: salmon, trout, shrimp, cod, anchovies, and canned light tuna.
  • Salmonella: Salmonella is the most common foodborne illness in the world and can spread through raw seafood present in sushi too. A recent Salmonella sushi outbreak occurred in 2015 and sickened 62 people. Frozen tuna infected with Salmonella was the culprit.
  • Staphylococcus Aureus: This illness is usually associated with rice and not seafood. Rice becomes contaminated with this bacteria when it is not chilled soon after cooking. Symptoms of this infection include: vomiting, nausea and stomach pain. Staph infection is generally treated at home with intake of lots of fluids. Sometimes, the sickened individual might need hospitalization to receive IV’s.
  • Hepatitis A: Hepatitis A is spread when cold, under processed and undercooked foods are handled by people who don’t wash their hands properly after using the bathroom. Hepatitis A is viral liver disease that can result in an epidemic if action is not taken soon. A recent Hepatitis A outbreak in the US occurred in 2016 due to frozen strawberries.

Tips to Prevent Sushi-Related Foodborne Illnesses

  • The FDA requires all fish to be frozen at -4℉ for 7 days or -31℉ for a minimum of 15 hours before using it raw. This temperature kills all the parasites and also keeps the fish fresh. Home freezers generally don’t work as well, so it’s not recommended to freeze fresh fish at home and then use it. Salting and marinating will also not remove parasites. Eating farmed fish rather than wild fish can also help reduce the chances of Anisakiasis.
  • Some properly trained chefs can detect the Anisakis Larvae, but not all can. Therefore, eating at high-end restaurants can also sometimes lower the risk of developing an infection from sushi.
  • Properly cooked seafood is usually pretty safe. Most seafood should be cooked to an internal temperature of 74℃. How can you tell? Well:
    • Fish is done when it separates into flakes and appears opaque throughout.
    • Cooked shrimp will develop pearly and opaque flesh.
    • Cook clams, mussels and oysters until their shells open. Discard any that don’t open.
    • Prawns and lobsters turn red when cooked; the flesh becomes pearly opaque.
    • Scallops appear milky white or opaque and firm.
    • As always, food thermometers are a good idea to check the internal temperature of the fish.
  • Take extra precaution while traveling and avoid eating seafood or meat from local restaurants around.
  • Choose:
    • Saltwater Fish: They have a lower risk of infection than freshwater fish.
    • Atlantic Ocean fish over Pacific Ocean fish since Atlantic has less population and hence, fewer parasites.
    • Sashimi Grade Fish: These fish generally meet all the FDA measures for processing and storing fish.

Asking questions about the origin of the fish and how they have been prepared is another way to keep yourself protected. It is a good idea to seek medical attention as soon as possible once any symptoms show to prevent long-term complications.

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