Dangers Of Eating Raw Fish

Is eating raw fish really safe? Are there diseases that one can contract by eating raw fish? 

There are infectious diseases that one can contract from raw fish. Thus, the safest way to eat fish, like meat, is to cook them thoroughly because cooking kills the disease-causing bacteria, viruses and parasites that infect fish.  However, people who, like your husband, enjoy eating fish raw can reduce their risks of getting sick by getting well-informed about these infections and observing precautionary measures to minimize their occurrence.

To start with, not all fish can be eaten raw. Fish lovers should refrain from eating freshwater fish raw because a variety of tapeworms that can be transmitted to humans infest them. In Japan where eating raw fish is part of the national cuisine, almost no freshwater fish is used for sushi and sashimi. Filipinos are therefore well-advised to follow suit.

Disease causing bacteria and viruses that can cause food poisoning and hepatitis can grow in stale and poorly handled fish. Contamination of fish with these pathogens can occur at any time during its handling, storage or preparation. The usual causes of contamination with disease-causing microorganisms of raw fish include poor personal hygiene of people who handle and prepare the fish, improper cleaning of storage and preparation areas and unclean utensils.

Although saltwater fish are safer to eat raw than their freshwater counterparts, a number of parasites can be contracted from them.  Parasitic infections by raw saltwater fish involves mainly three kinds of parasites: Clonorchissinensis (a trematode/fluke), Anisakis (a nematode/roundworm) and Diphyllobothrium (a cestode/tapeworm). Of these, anisakis, a parasitic roundworm that may invade the gastrointestinal tract of humans, causing mild to serious complications is of highest concern at present. But the actual risk of getting infected with anisakis by eating raw or undercooked fish is actually very small; in the U.S. for example, less than 10 cases of the infection are diagnosed each year. Infection risk of anisakis is higher in saltwater fish that spend part of their lives in a river such as salmon and mackerel.

Anisakis reside in the gut of the fish while the fish is alive. It is only when the fish dies that their larvae, the form of the parasite that is infective to humans, migrate to the meat. Thus, gutting fish as soon as they are caught reduces the risk from anisakis greatly. It is also possible to remove anisakis larvae from fish as it is being prepared because they are visible to the trained eye.

To ensure that the raw fish you eat is safe, eat only in reputable restaurants, but if you wish to prepare raw fish yourself, you should observe the following measures:

• Buy only sushi-grade fish. Sushi-grade fish are caught quickly, bled upon capture, gutted soon after and iced thoroughly. In addition, sushi-grade fish are frozen to destroy the parasites that they may harbor. The recommended procedure is to freeze fish at temperatures of -20oC or below for seven days or -35oC or below for 15 hours or -35oC until frozen and held at -20oC for 24 hours.

• Defrost fish in the refrigerator. Do not take them out of the ref and thaw them under room temperature.

• Wash hands thoroughly with soap and water prior to preparing raw fish and after using the toilet, smoking, eating and touching non-food items.

• Wash with soap and water all utensils, chopping boards and kitchen areas before you use them to prepare raw fish.

By EDUARDO GONZALES, MD

mb.com.ph

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