By Muleme
Michael
My advice
to the consumer will depend on the several factors. The factors include the
country in which the restaurant is located, her health status, age and
conditions like pregnancy. The
implementation of food regulations varies from place to place. In most developing
countries the food regulations are outdated or human, infrastructural and
financial constraints affect the implementation of food safety laws (5). The consumer should therefore not
eat raw fish products in any restaurant in these countries.
In the
United States and countries within the European Union where food safety standards
are strictly adhered to, it may be safe to have sushi and other raw fish
products in a restaurant (11). The US
food and Drug code requires fish for raw consumption to be frozen at -35oC
for 15 hours or at less than -20oC for 7 days while the European
Union’s Hazard Analysis point for marine fish to be eaten raw is freezing at
less than -20oC for 24 hours (4,
14). Various studies have shown freezing to be effective against many
parasites feared in raw fish products (3,
6, 8). However it should be noted that all parts of the product must be
subjected to the recommended temperatures which may not be the case in all
freezing facilities even within restaurants in the United States. Studies have
shown that temperatures higher than -17oC are not effective against Anisakis larvae (2, 6). Additionally
freezing may not protect against allergic reactions that may develop due to ingestion
of dead parasite larvae (1, 2). Thus
the consumer should know that although minimal, there are chances of infection
with foodborne parasites or allergy reactions from eating raw fish in
restaurants that use the freezing criteria (11).
Dewormers like albendazole and praziquantel have been shown to be effective
against most of these zoonotic parasites (10,
11). Therefore with regular deworming, the risk acquiring foodborne
parasitic infections from the consumption raw fish from restaurants is very
minimal in countries where food safety regulations are strictly implemented.
A number
of parasitic zoonoses are known to be transmitted through the consumption of
raw fish. These include round worms (Anisakis
spp.), tapeworm (Diphyllobothrium
latum) and liverfluke (Clonorchis
spp, and Opisthorchis spp) infestations (9,
11, 13). These are mainly endemic in the Asia (9) but the existence of these parasitic infections elsewhere
cannot be ruled out. Of late many of these cases are reported due to modern
diagnostic techniques like endoscopy rather than the actual increase in number
of parasitic infections (11, 12). In
the United States, these have been identified in travelers and immigrants (13); however, the possibility of
getting these infections from sushi restaurants within the United States cannot
be ruled out. This is because fish borne
parasitic infections are not reportable within the United States and no
national estimates of cases have been published (9). Thus I would recommend that it is not safe for pregnant women,
immune-compromised individuals, and the aged to eat raw fish products even from
the restaurants. The consequences of the symptoms seen in some of the parasitic
infections from raw fish consumption like anemia and gastroenteritis (11) may be fatal in pregnant women,
immune-compromised, aged and infants. Additionally the treatment of these
parasitic infections may harm the fetus (9).
A survey done by Jones et.al (9)
showed that 81.5% of obstetric-gynecologists acknowledged that eating raw fish
during pregnancy is not safe. Until this is disproved scientifically, the
findings of this survey should not be ignored by consumers. Similarly children
may be adversely affected by these infections and allergic hazards of dead
parasites in raw fish due to either their under-developed immune system or
naïve immunity to the pathogens (7).
The
articles by Gustafson, Houwing, Deardorff and Throm, demonstrated the
effectiveness of freezing against most parasites in raw fish (3, 6, 8). Some of these experiments
like that Deardorff and Throm (3) showed
100 per cent effectiveness and was published in peer reviewed journals. Deardoff and Throm, (3) found no viable Anisakis
larvae in 3545 salmon and rockfish stored at -18OC for 1 hour. Thus
freezing may be effective against larvae. The consumer should therefore worry
about minimal risks due to failure to subject all parts of the fish to the
recommended temperatures, equipment failure in restaurants and allergic hazards
due to dead parasites. Children, immune compromised people and pregnant women
should not be exposed to these risks however minimal they are. Additionally
other viral and bacterial infections like hepatitis A virus, Salmonella and
Campylobacter may present serious foodborne hazards especially in unhygienic
restaurants.
References:
1.
Audicana, L., M. T. Audicanna, L. Fernandez de
Corres, and M. W. Kennedy. 1997. Cooking and freezing may not protect against
allergenic reactions to ingested Anisakis simplex antigens in humans. Vet. Rec. 140:235
2.
Beldsoe, G., and P. M. Oria. 2001. Potential
hazards in cold-smoked fish parasites. J.
Food. Sci. Suppl. 66:s1100-1103
3.
Deardorff, T. L., and R. Throm. 1988.
Commercial blast-freezing of third-stage Anisakis simplex larvae encapsulated
in salmon and rockfish. J. Parasitol.
74:600-603
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