Seafood Safety
latum tapeworm
Description
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).
ADULT
------> 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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