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Raw Fish and Tapeworms

Fish infected with the parasite Diphyllobothrium latum leads to the parasitic infection called diphyllobothriasis, also known as a fish tapeworm, if their flesh is consumed raw. Fish tapeworm infections are found in Chile, Peru, Uganda and in the northern hemisphere across the globe in areas of fresh water. Scientists have identified several different species of fish tapeworms, which can all lead to infections.

  1. About Tapeworms

    • Tapeworms are very small -- only 3 mm wide.

      Tapeworms can live inside the intestines of a human host for decades if left untreated, and can grow to lengths of 10 meters or more. They have long, flat segmented bodies that produce new growth from the neck region. They attach to the intestinal walls of humans using two shallow muscular grooves near their mouths called bothria.

    Life Cycle of a Fish Tapeworm

    • Tapeworms lay up to a million eggs in one day, which are passed through the feces of an infected person who serves as the first host. These eggs mature into oncospheres in water within three weeks, and are consumed by small freshwater crustaceans, which serve as the second host. The oncospheres mature into coracidia larvae once they are inside the crustaceans. The crustaceans are eaten by fish, where the coracidia develop into procercoid larvae. From here, the larvae burrow through the fish's gut to its muscle. If this flesh is eaten raw, the larvae mature into adult tapeworms in the intestines of a human.

    Symptoms of Tapeworm Infection

    • Once a person is infected, it takes approximately six weeks for the eggs to appear in fecal matter. Sometimes a tapeworm infection will produce no symptoms. Other times, infected persons will exhibit extreme cases of constipation, diarrhea, fatigue, bowel obstructions, stomach pain, vomiting and weight loss. These can lead to more severe side effects such as gradual anemia and inflammation of the bile duct and gall bladder. Tapeworms absorb a lot of the B12 in foods before the host human's intestines can, which contributes to anemia.

    Diagnosis and Treatment

    • A medical facility will test a stool sample for tapeworm eggs or sloughed body sections from the tapeworm. There should be enough eggs in the sample because of the amount of eggs one tapeworm produces in a single day. Some tapeworms will leave the host body on their own, but others require prescription drug treatment. The most common drugs used are praziquantel and albendazole, which are harmful to the adult tapeworm but not to the human host. The type of drug used depends on the species of tapeworm and the site of infection.

    Prevention

    • The plerocercoid larvae is killed when fish flesh is heated past 145 degrees Fahrenheit. It can also be killed if the meat is frozen at 14 degrees Fahrenheit or colder for two days. Refrain from defecating in water in case you are infected and do not know it; this prevents the eggs from being introduced to their next hosts in their life cycle.

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