Consumption of raw fish in the supposed form of "sushi" and "sashimi" is
spreading all over the world. A word of caution is necessary regarding the
possible hazard of parasites in raw fish consumed that way: (1) outside Japan
the supposed "Japanese conditions" are not necessarily the same cultural,
hygienic and regulatory (control) conditions; (2) there is no possibility to
generalize "urbi et orbi" regarding the possible occurrence of parasites of
interest to human health (both in fresh water and marine environments); and
(3) fraud (specie substitution) can not be ruled out as possibility.
Of particular concern is the consumption of raw fish in developing countries
particularly in the cases where fish inspection services do not have the
resources to practice and effective surveillance and control, or where
HACCP-based regulations for the internal market are not in place.
Of particular concern could be for instance Diphyllobothrium spp parasites.
Recently has been published a study in Brazil: "Diphyllobothrium spp.: an
emerging parasite in Sao Paulo, associated to raw fish consumption - Sushis
and Sashimis"; de Paula Eduardo, M.B. et al.; Boletim Epidemiológico Paulista
(BEPA) 2; No 15; March 2005 pp 2-5 (in Portuguese) (can be downloaded free
from: http://www.cve.saude.sp.gov.br/agencia/bepa15_diphy.htm ).
Diphyllobothriasis, in particular from D. dendriticum could be expected in
circumpolar area at high altitudes. Other additional parasite species are
also implicated in human infections in northern communities bordering the
Pacific: D. ursi from Northern Canada and Alaska; D. dalliae from Alaska and
Siberia and D. klebanovskii from Siberia. Larvae of D. dendriticum occur
predominantly in salmonid fish (e.g. artic char, salmon, trout and some white
fish). D. ursi and D. klebanovskii predominantly occur in Pacific salmon and
D. dalliae in Alaskan blackfish. See: "Diphyllobothriasis: fish tapeworm
disease in the circumpolar north. Curtis, M.A.; Blyund, G.. Artic Med. Res.
1991 Jan, 50 (1): 18-24.
D. dendriticum also appears in wild Atlantic salmon (Salmo salar) as could be
seen for instance from the site of the Maine State (US):
http://www.maine.gov/ifw/fishing/fishlab/vol4issue1.htm .
Of course it is well known the hazard of D. latum in fresh water fish of the
Northern Hemisphere (no need to be discussed here).
In the Southern Hemisphere it can be found a similar situation, where in
addition to D. latum (fresh water fish); D. dendriticum there is the
possibility of D. pacificum (sea water fish). Human infections with D.
pacificum due to the consumption of raw fish or fish consumed as "ceviche"
(raw fish plus salt and lemon) have been reported particularly in Chile and
Peru. See for instance:
Sagua F., H. et al. "Diphyllobothrium pacificum: infection in a 3 year old
boy in Antofagasta, Chile". Rev. chil. pediatr. v. 71 n. 5 Santiago, set.
2000
(in Spanish with abstract in English). Can be downloaded free from:
http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0370-4106200000050000
9&lng=en&nrm=iso
Sagua F., H. et al. "New cases of Diphyllobothrium pacificum (Nybelin, 1931)
Margolis, 1956 human infection in North of Chile, probably related with El
Niño phenomenon, 1975-2000". Bol. chil. parasitol. v. 56 n. 1-2, Santiago ene
2001. (in Spanish with abstract in English). Can be downloaded free from:
http://www.scielo.cl/scielo.php?pid=S0365-94022001000100006&script=sci_arttex
t&tlng=es
Revenga, JE. "Diphyllobothrium dendriticum and Diphyllobothrium latum in
fishes from southern Argentina; association, abundance, distribution,
pathological effects and risk of human infection". J. Parasitol. 1993 Jun; 79
(3): 379-83
Semenas, L. and Ubeda, C. "Human diphyllobothriasis in Patagonia, Argentina".
Re, Saúde Pública vol. 31 no. 3 São Paulo (Brasil) June 1997. (In Spanish
with abstract in English). Can be downloaded free from:
http://www.scielosp.org/scielo.php?pid=S0034-89101997000300012&script=sci_art
text&tlng=es
(In these publications there a some other papers related to the subject).
The possibility of infection of parasites from fresh water fish, including
those from aquaculture, particularly in the S.E. Asiatic context, can be seen
from the "Food safety issues associated with products from aquaculture,
report of a Joint FAO/ NACA/ WHO study group, 1999. The full report can be
downloaded from:
http://www.who.int/foodsafety/publications/fs_management/aquaculture/en/index
.html
There is a discussion about the possibility of marine Diphyllobothrium spp
could infect commercial salmon. Even if feeds (trash fish) are controlled the
potential possibility exist in the sense that intermediaries of the parasite
could infect some copepods that in turn may infect the salmon or eventually
other fish in cages. Water temperature seems to be critical in the
possibility of existence of copepods with intermediaries of the parasite. A
paper discussing this subject is: Dorucu, M. "Seasonal variation of
Pseudophyllidean cestode, Diphyllobothrium spp. Infection in Cyclops strenuus
abyssorum (Copepoda) in Loch Lomond". Tr. J. of Zoology 23 (1999) 85-91. A
copy of this paper can be downloaded free from:
http://journals.tubitak.gov.tr/zoology/issues/zoo-99-23-1/zoo-23-1-11-97030.p
df
Reservation and care in discussing this point can be understood because it
involves the core of commercial aquaculture in cold and temperate regions. It
is known that fish inspection services monitor the possible presence of
parasites in aquaculture salmon. Producers also express that parasites will
affect in first place the fish and that they will know of this situation and
correct it, and that is in their own interest.
As consumer it is interesting to be reassured about the control of this
potential possibility and I do not doubt that most of the salmon production
is parasite (D. spp) free (otherwise we would know of the problem as a rise
in diphyllobothriasis); but from the point of Risk Analysis it would be
interesting to know which could be the actual risks to eat raw fish.
Consumers (Risk Communication) would like to have a clear picture, and it
could become an issue if a single case appears in a developed country and the
news reach the press.
When we talk that some form of control exists is because there is no zero
risk for that hazard. May be the risk assessment exists and I do not know it
(surely at least some form of qualitative risk assessment for this hazard
exists in the files of more than one of the fish inspection services of
developed countries). Personally I would be more afraid, in this case (raw
fish consumption), of:
(i) Wild salmon and wild fish in general, in particular wild fresh water
fish.
(ii) Fraud, voluntary or non-voluntary, this means fish (e.g. fresh water
salmonids) presented as "salmon". Fresh water salmonids are in general
cheaper than salmon.
In any case if we sum up all the situation the best advice could be/ is not
to eat raw fish that have not been frozen before (according to existing local
regulations and/ or recommendations). I wrote "could be/ is" because there is
in some countries a strong cultural component here, and food convey many
aspects (not only hazards). I do not eat currently raw fish, even if I have
tested a number of raw fish with research purposes (long time ago) or due to
"diplomatic/ politically correct" reasons (no so long ago).
Hector M. Lupin
Senior Fishery Industry Officer (Quality Assurance)
Fish Utilization and Marketing Service (FIIU)
Fishery Industries Division (FI)
Fisheries Department, FAO, Room F 606
Viale delle Terme di Caracalla
00100 Rome, Italy
Tel + 39 06 570 56459
Fax + 39 06 570 55188
E-mail: hector.lupin@fao.org
-----Original Message-----
From: owner-seafood@ucdavis.edu [mailto:owner-seafood@ucdavis.edu] On Behalf
Of P Howgate
Sent: 26 July 2005 21:37
To: Jin Kim; seafood@ucdavis.edu
Subject: Re: Fish for raw consumption in US
Yes, I agree. You will see from my message that I am not entirely happy with
the EU derogation of farmed salmon from the requirement of freezing before
using raw. I don't think bird droppings transmit nematode parasites, but I
do not think you can rule out that fish reared in sea cages will
occasionally have the opportunity to consume wild food. Also I think some
fish farmers make up their own feeds and they might use raw trash fish. The
derogation should not be for farmed salmon as such, but for farmed salmon,
or perhaps other species of farmed fish, that has been fed only with
pelleted feeds, or with heat processed or previously frozen fish or fish
offal.
Peter
----- Original Message -----
From: "Jin Kim" <jkim@spa.ars.usda.gov>
To: <phowgate@clara.co.uk>; <seafood@ucdavis.edu>
Sent: Tuesday, July 26, 2005 8:23 PM
Subject: Re: Fish for raw consumption in US
What I meant in my comment was I would like FDA in the future to require all
fish frozen for safety if it is intended to consume as raw. That is my
personal opinion. Feed is extrusion-cooked and safe, but how about many
different kinds of bird's droppings in floating pens of salmon farming and
in pond of land-based different fish farming. One fish was infested in a
major study in the case of farmed Atlantic salmon as Hans Morten Henriksen
mentioned. If someone eats that fish, that person is going to be sick. If a
portion of the fillet is served some other people, they may get sick.
I saw many species of fish caught off-coast of Alaska were infested by
parasites. Most sashimi restaurants in Anchorage don't use fish right from
their coast, but ship the fish from Seattle and West Coast of the US to
serve at their restaurants. What happens if someone serves fish from there
without previous freezing. There could be many non-reported food-borne
disease caused by these parasites.
I hope University Seafood Extension obtain funds to organize and train
sashimi restaurant chef how to freeze and thaw all fish species for serving
so that raw fish can be served without much quality deterioration.
Jin Kim
USDA-ARS-ASRU
Pine Bluff, AR 71601
jkim@spa.ars.usda.gov
>>> "P Howgate" <phowgate@clara.co.uk> 07/26/05 09:39AM >>>
In the EU farmed Atlantic salmon need not be frozen before consumption in the
raw or lightly processed states because surveys have shown that such salmon
are free from nematode parasites. Nematode parasites are transmitted to the
host fish through consumption of parasitised prey fish, and likewise other
species of farmed fish should also be free of nematode parasites, but only
provided they have been fed on processed feeds, as distinct from unprocessed,
raw, feeds or, presumably, previously frozen raw feeds. I would still be wary
of such derogations from the best practice of prior freezing of fish destined
for raw or lightly processed products unless the specific combination species
and cultural practices had been demonstrated to be safe.
I would agree that the texture of fish frozen according to the requirements
to inactivate trematode parasites - holding at -18 or below for 24 hours -
would be little changed compared with the unfrozen counterpart, and any
change would anyway be well within the natural variation in texture of the
species in question. This observation is based on my experience of attempting
to measure the effects of the freeing/thawing cycle alone, as distinct from
the from the effects of storage in the frozen state, on texture of fish. If
the fish is frozen and thawed under good practices - frozen rapidly and
thawed rapidly - any affects of the freeze/thaw cycle is difficult to detect
even by an experience laboratory panel, and only then when data are pooled
over several samples.
Peter Howgate
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