Who does not love a bargain – buy one, get one free? Here is a great bargain that has escaped the eye of fish eaters. For every fish you eat, you get a couple of worms as well which stay alive long after the fish is dead. 

How serious is the problem of worms in fish? An international standard, Codex Alimentarius, allows a maximum of 5 worms of more than 1 cm in length in 1 kg of fish. Why is there no warning on fish? Would you buy fish if it had a warning on it about worms? 

The most common are roundworms, tapeworms and flukes.

Roundworms are of the Anisakis family. Anisakis simplex or herring worm is found in all warm water fish like herrings, mackerels and whitings and a large number of coldwater fish as well. It is found in all nearshore fish. It grows up to 2 cm long , is almost colourless, and is found tightly coiled and encased in the guts and flesh.
Rhexanella verrucosa is a hooked worm that attaches itself to the tongue of the fish and helps itself to whatever the host fish eats. 

The Phocanema worm or codworm grows up to 4 cm long and varies in colour from creamy white to dark brown. It curls up and encases itself in a sac-like membrane produced by fish tissue. Most fillets( boneless pieces) , specially mackerel fillets are infested with these skinny milky colour see-through one inch long coiled worms. 

The fish eater can pull the large ones out – if you are watching out for them. But if you buy them from on ice they stay tightly coiled within the flesh of the fish so you only see the red or black pinhead on the body of the fish. Anisakis larvae are resistant to salting. So are anchor worms which are thread-like worms that attach themselves to the head of the fish. Never pull out the worms using force, since the head of the worm will stay attached to the head of the fish and grow a new body. 

The fish industry does not deny that there are worms in fish. They claim that they are harmless if eaten ( after all , if you can survive the mercury and the human feces in fish , then what are a couple of worms ?) as long as the fish is cooked. But there have been many cases reported in which worms – anisakids – have been found wriggling around in fish that have been microwaved. When there are worms in the fish, it is also likely there are eggs, too. They withstand heat better than mature worms so are more likely to be ingested while still viable. Roundworms in ?sh may be found in muscle tissues, in internal organs, or in the intestinal tract. When chilled, they stay tightly coiled within the flesh of the fish. As they warm up, they come wriggling out to be seen. 
Another typical fish parasite is the fish tapeworm. It can live many years in the intestines. There is a worm called giant stomach worm (Hirudinella ventricosa) which can grow to longer than a man’s hand. Freshwater fish like trout and salmon may carry tapeworm larvae. These are small, whitish, and somewhat flabby worms that can live in the human intestinal tract for several years. Symptoms can include abdominal pain, weakness, weight loss and anemia.  

Flukes are among the largest groups of parasites affecting marine ?shes. Flukes are similar in shape to tapeworms, but are shorter and broader. Some ?ukes are enveloped in cysts and can be seen only through a microscope. The dark pigments that occasionally appear around these cysts can be seen with the naked eye and is referred to as “black spot disease.” 

Flatworms are transparent when alive, but turn white when they die: Heavy infections cause irritability, and anorexia. Gill flukes are brown , thin flatworms that look like tiny blobs and feed on blood. Infections can cause emaciation, lethargy and anaemia. Sea-lice scuttle around on the surface of the fish and can cause irritation and anaemia in heavy infections. All these can be removed from the fish by using hydrogen peroxide but to dip your fish in that and then eat it would cause its own problems.

What are the effects on human beings. Anisakiasis is a parasitic infection of the gastrointestinal tract which causes stomach flu like symptoms and permanent allergic reactions to chemicals left by the worms in fish flesh. The symptoms of these disease are : Within hours after ingestion of infective larvae, violent abdominal pain, nausea, and vomiting may occur. Occasionally the larvae are coughed up. If the larvae pass into the bowel, a severe allergic response may also occur 1 to 2 weeks following infection, causing symptoms mimicking Crohn's disease. Acute allergic manifestations such as urticaria(rash) and anaphylaxis (shortness of breath)may occur with or without gastrointestinal symptoms. Asthma, conjunctivitis, and contact dermatitis have been observed in fish processing workers who come into contact with live worms. In some cases infection can lead to small bowel obstruction, which may require surgery. 

Codworms are particularly common in white fish , cod, haddock, flounder, sole, and halibut, swordfish and monkfish. If you examine tuna you will probably see wriggling, very narrow pink worms. Deep sea fish like salmon have dark coiled worms . Frozen flounder fillets have little circles on them with a small reddish string in the center of the circle which unwinds and moves out of the circle. In shrimps , the parasites are too small to see but all fish ranging from sardines to squid ,cuttlefish and sharks have them. Warmwater fish that typically harbor parasites are mackerel, sea trout, shrimp, and eel, amberjack., catfish large saltwater fish. Worms appear like thin white strings. The most common fish to be infected with tapeworm are salmon, pike, perch, lake trout, grayling, orange roughy, and turbot. If you see spots in the muscle, those are worms. German television recently did a s series on worms in supermarket fish. They showed worm larvae in the bellies and flesh, as well as live ones in jars of pickled herring in the supermarket . 

If you eat lightly cooked fish – sushi or sashimi - you probably will swallow live worms. The only way to reduce the numbers of worms is to inspect the fish . Visual inspection of fillets will reveal worms embedded near the surface; these can be removed easily with a knife. Worms embedded deep in the flesh are not immediately obvious, but some can be detected by candling, that is, shining a bright light through the meat. Worms show up as dark shadows in the flesh, and can be removed with forceps or a knife.  

Happy eating!

Maneka Gandhi

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