Seafood Safety

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latum tapeworm


Diphyllobothrium latum is a cestode, or tapeworm, which parasitizes a variety of piscivorous mammals of the upper northern latitudes (Olson, 1986). Cestodes are flatworms which have an anterior attachment structure, called the scolex, and body segments, called proglottides. Cestodes found in infected fish range from a few millimeters to several centimeters in length (Olson, 1986).

Contaminated Species

Most Diphyllobothrium tapeworms infect freshwater fish, however, anadromous salmonid fish can also carry the parasite (Schantz, 1989; Olson, 1986). Diphyllobothrium tapeworms are usually found unencysted and coiled in musculature, or encysted in viscera.

Life Cycle

Adult Diphyllobothrium live in the intestine of a variety of fish-eating mammals and birds. Eggs are passed in the feces and develop to coracidium, or ciliated larvae, in the water. The larvae are consumed by crustaceans, usually copepods. In the digestive tract of the crustaceans, the larvae develop to the first tapeworm stage, called the procercoid. Fish become the second intermediate hosts by consuming infected crustaceans. The pleurocercoid, or second tapeworm stage, develops in the fish. Birds and mammals (including humans) become the final hosts by consuming fish containing the pleurocercoid (Olson, 1986).
    ------> Mammals & Birds ------> Eggs passed
    |                                      | in feces
    |                                      v
    PLEUROCERCOID                           CORACIDIUM
        Fish                                 Seawater
    ^                                      |
    |               PROCERCOID             v
    <------ Crustaceans <------
Symptoms & Treatment
Most cases of human Diphyllobothrium infection are asymptomatic (Schmidt and Roberts, 1985 as cited in Olson, 1986). However, some individuals experience abdominal pain, diarrhea, constipation and occasional megaloblastic anemia. Examination of eggs and proglottides in the feces of affected individuals provides diagnosis of tapeworm genus only. In order to determine the species, it is necessary to examine the scolex (Matsui et al., 1985 as cited in Olson, 1986). Cases of human infection have been successfully treated with anthelminthic drugs (Schantz, 1989).
Detection & Prevention

Salmonid fish should be thoroughly cooked to avoid infection. No precise information on the freezing temperature tolerance of Diphyllobothrium is available.

This is long so I had to break it up, Part 2 .

This is long so I had to break it up, Part 2 .

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