What is a fish tapeworm?

Fish tapeworms include a number of species in the Diphyllobothrium family. The most common fish tapeworm in humans is a species called Diphyllobothrium latum . It causes a disease in humans called diphyllobothriasis. Doctors treat the infection with antiparasitic drugs.

Diphyllobothriasis occurs in populations around the world. People become infected with fish tapeworms by eating undercooked or uncooked freshwater fish that is contaminated with tapeworm cysts, which are embryonic tapeworms. The worm can live inside the human intestine for several decades.

Fish tapeworms require more than one host to mature. They begin their lives as eggs and mature into six-hooked embryos called coracidia. They must be eaten by a crustacean before they can begin the next part of their development and mature into first-stage procercoid larvae.

Small freshwater fish become the second intermediate host for tapeworms by consuming infested crustaceans. The worm matures into a sparganum or plerocercoid within these fish. The larger fish consume the smaller fish, and eventually the fish could be caught, and a human could eat the fish containing the sparganum. The immature worm grows within the intestine, maturing into a segmented worm that reaches lengths of 25-30 feet (7.62-9.14 m).

Each segment of the worm, or proglottid, produces eggs. A mature fish tapeworm is capable of producing more than a million eggs each day. These eggs pass out of the body through feces.

Most people who have a fish tapeworm do not know they are infected. Some people may have generalized symptoms, such as stomach pain, loss of weight or appetite, and lack of energy, and others suffer from anemia or vitamin B-12 deficiency. Patients may also see proglottids in their stool.

Doctors diagnose diphyllobothriasis by examining a stool sample. They treat the condition with medications such as praziquantel, niclosamide, and albendazole. These drugs don't always succeed in separating the worm's head from the intestinal wall, and the worm can grow back if its head is still attached. Some doctors use injections of diatrizoic acid to separate the entire worm so that nothing can grow back.

Raw fish is the main ingredient in many regional cuisines. People who enjoy these dishes can avoid fish tapeworms by freezing fish for 24 hours at a temperature of about minus 4 degrees Fahrenheit (minus 20 degrees Celsius) before preparing the dish. Substituting raw saltwater species for freshwater fish will also help prevent infections, because saltwater fish do not carry fish tapeworms. Cooking fish for about five minutes at 140 degrees Fahrenheit (60 degrees Celsius) will kill tapeworm eggs.

Go up