Hepatitis
A is an infectious disease affecting
the liver caused by hepatitis A virus
(HAV).
2.
Food
borne transmission through faecal-oral
route is the most important mode of
transmission for hepatitis A.
3.
Hepatitis
A may be asymptomatic, or produces acute
symptoms depending on the age of the
infected persons. Adults exhibit more
severe symptoms while infants usually
show no signs.
4.
The
incubation period of the disease ranges
from two to six weeks. Symptoms can
include fatigue, poor appetite, nausea,
vomiting, diarrhoea, abdominal discomfort,
jaundice and tea-coloured urine.
5.
Because
of its unique habitat and special feeding
mechanism, shellfish especially bivalve
shellfish is an important vehicle responsible
for transmission of hepatitis A.
Risk
Assessment and Public Health Significance
1.
Shellfish
is a broad term for all aquatic animals
that have a shell of some kind. It generally
divided into four groups namely crustaceans
(examples: crabs, crayfish, lobster,
and shrimp), gastropods (examples: abalone,
limpet, snail, and whelk), bivalves
(examples: oysters, clams, mussels,
and scallops), and cephalopods (examples:
octopus, squid, and cuttlefish).
2.
Shellfish
living in water contaminated by sewage
can carry the HAV. Because bivalve shellfish
are filter feeders, they absorb food
particles and nutrients by filtering
out the seawater. Hence they tend to
concentrate the virus present in the
polluted water. Man may contract hepatitis
A after consumption of contaminated
shellfish that has not been thoroughly
cooked. Consumption of bivalve shellfish,
like cockles, oysters and clams, is
strongly associated with hepatitis A
outbreaks.
3.
Attention
to environmental, food and personal
hygiene can prevent hepatitis A. When
handled properly, shellfish is as safe
to eat as any other source of food.
Control
Measures and Surveillance Findings
1.
Under the
Public Health and Municipal Services
Ordinance, Cap.132, fresh or frozen
shellfish is classified as a restricted
food item, which is subject to licensing
control.
2.
At the
import level, we strongly encourage
importers to obtain health certificates
issued by health authorities of the
countries of origin certifying that
each imported consignment of shellfish
is fit for human consumption.
3.
When a
consignment of shellfish arrives at
entry points, it may be subject to inspection
or sampling by us. If the importer concerned
is unable to present a health certificate
for inspection, we may take samples
from the consignment for examination
before its release.
4.
We take
regular samples of shellfish both from
the retail outlets and at the entry
points for testing of HAV. From 1999
to June 2000, 809 samples of shellfish
(including 734 samples of bivalve shellfish)
were taken for HAV testing. 92 samples
(11.4%) were found unsatisfactory. All
these unsatisfactory samples were bivalves.
The surveillance findings reflected
that bivalve is more vulnerable to HAV
contamination than other groups of shellfish.
Advice
to the Public
1.
Buy only
those shellfish which are fresh, with
intact shell and free from abnormal
odour.
2.
Do not
buy shellfish from illegal hawkers and
unlicensed food premises.
3.
Scrub and
rinse the shellfish in clean water.
4.
All shellfish
should be cooked at boiling temperature
for not less than five minutes before
eating.
5.
Mud oysters
should not be eaten raw.
6.
If possible,
remove the shells before cooking as
they impede heat penetration.
7.
Remove
the viscera of the shellfish before
cooking.
8.
When having
hotpot, use separate chopsticks and
utensils for handling raw and cooked
food to avoid cross contamination.
Advice
to the Trade
1.
Do not
obtain the supply of shellfish from
unreliable sources.
2.
Importers
should obtain health certificates from
the relevant health authorities certifying
the safety of each consignment of shellfish.
3.
Observe
good manufacturing, preparation and
hygiene practices.
4.
Observe
hygienic practice during food preparation
and storage.
Last
review date: 19-01-2005