Home' Trinidad and Tobago Guardian : January 13th 2017 Contents A26 body & soul
guardian.co.tt Friday, January 13, 2017
US salmon may carry
If you eat raw or undercooked fish,
you risk developing an infection
One of the most gruesome is tape-
worm, a species of digestive tract-in-
vading parasites that includes Diphyllo-
bothrium nihonkaiense, or the Japanese
Though this worm was commonly be-
lieved to infect only fish in Asia, a study
published Wednesday in the Centers
for Disease Control and Prevention's
monthly journal Emerging Infectious
Diseases says wild salmon caught in
Alaska had also been infected by this
Based on those results, researchers
warn that salmon caught anywhere along
the Pacific coast of North America may
Meet the tapeworm
The most common fish tapeworm is
Diphyllobothrium latum. In 1986, scien-
tists identified another member of this
family, the Japanese broad tapeworm,
and believed it had been responsible
for about 2,000 infections reported to
that point, making it the second most
common cause of tapeworm infection.
However, continuing to study the
tapeworms using new molecular meth-
ods, researchers funded by the Czech
Science Foundation discovered they'd
Almost all of the previous cases of
tapeworm infections occurring in Ja-
pan, South Korea and the Pacific coast
of Russia had actually been caused by
Japanese tapeworms rather than D la-
tum. In fact, Japanese tapeworm larvae,
known as plerocercoids, could be found
in salmon caught off the coasts of eastern
Russia and Japan.
Could Japanese tapeworms also be
infecting salmon caught in the United
In July 2013, a team of scientists ex-
amined 64 wild Alaskan salmon. After
filleting the musculature into narrow
slices, the scientists observed these and
the internal organs of each fish under a
They discovered larvae, between eight
and 15 millimetres long, that continually
elongated and contracted (as worms are
known to do).
With gene sequencing, they were iden-
tified as Japanese tapeworms.
Based on the study results, four spe-
cies of Pacific salmon are known to car-
ry Japanese tapeworm infections: chum
salmon, masu salmon, pink salmon and
Because these salmon are exported
on ice---unfrozen---and then appear in
restaurants around the world, infections
caused by the Japanese tapeworm may
occur anywhere, from China to Europe,
from New Zealand to Ohio.
Few have symptoms
Compared with an infection resulting
from D latum, "we think this Japanese
version would not be any different, al-
though very little is actually known about
this variant of tapeworms," said Dr. Wil-
liam Schaffner, a professor of preventive
medicine at Vanderbilt University School
of Medicine who was not involved in the
Because the Japanese version is from
the same family of tapeworms, illness
and symptoms should be largely the
same, he said.
But D latum and related species (in-
cluding the Japanese tapeworm) can
grow up to 30 feet long, according to
"Actually, most of the people who
are infected don't have symptoms,"
Schaffner said. Some feel a little bit of
abdominal discomfort, some have nau-
sea or loose stools, and some even lose
a little weight.
Most often, tapeworm leads to only
minor symptoms, but in exceptional cas-
es the infection can turn into a serious
medical problem, according to Roman
Kuchta, lead author of the study and
a research scientist at the Academy of
Sciences of the Czech Republic.
"Massive infections may result in in-
testinal obstruction" and painful inflam-
mation of the bile ducts, said Kuchta.
"The infections can have a substantial
emotional impact on patients and their
families, because segments are evacuated
over a long period of time.
"More severe cases may require spe-
cialised consultations and complemen-
tary analyses, which are costly."
Along with emotional impact and ex-
penses, there's also the initial shock---
terror, really---of discovery.
"The reason you know you have tape-
worms is you look in your stool and
you find bits of tapeworm floating in
the water---and that usually panics you
enormously," Schaffner said. After all,
tapeworm infection is very unusual in
the United States.
After discovering that you're infected,
you can collect a sample from your toilet
bowl and send it to a lab for testing, and
then, with your doctor's help, the tape-
worm can be identified and "treated very
effectively," Schaffner said.
According to Dr Patrick Okolo, chief of
gastroenterology at Lenox Hill Hospital
in New York, the medications used are
not typical antibiotics but specialised
drugs targeting specific types of para-
Though the study suggests that in-
fections by Japanese tapeworm may be
much more common in the US than an-
ticipated, there's still "no evidence at all
about how common it is," Schaffner said.
"Is this a teeny-tiny proportion of the
population, or is this something the av-
erage family doctor better learn about?"
cooking or freezing
Those who prefer the safe side can
stick with adequately frozen or cooked
fish, according to the CDC.
"Cooking for 145 Fahrenheit for four or
five minutes will destroy the tapeworm,"
said Okolo, who was also not involved
in the study.
"Freezing fish under certain condi-
tions will also destroy the worm and its
Schaffner admits the new study has
given him "a little bit of pause---because
I like salmon sushi."
He said talk of "emerging in-
fections" or new infections comes
about, in part, because new scien-
tific methods are able to identify
This view is supported by Jayde
Ferguson, a co-author of the new
study and a scientist at Alaska De-
partment of Fish and Game.
"The tapeworm itself is probably
not new---it's just that more skilled
parasitologists started looking for
it. Identifying these parasites is
challenging," said Ferguson. "This
was simply a more detailed eval-
uation of the Diphyllobothrium
that has occurred here for over a
Still, there's another important
reason "old" infections from one
part of the globe emerge as "new"
infections on another part of the
globe, said Schaffner.
"Because we do things that we
haven't done before," Schaffner
"Now, we have these fresh caught
fish that can be transported any-
where and eaten raw. ... I am sure
we will be on the lookout for this
kind of tapeworm going forward."
Cook salmon at 145F for four or five minutes to destroy the tapeworm.
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