1 Recent International Efforts to Improve Bivalve Molluscan Shellfish Safety
5
Table 1.1 Predicted and reported illness due to V. parahaemolyticus following consumption
of oysters in selected countries (FAO/WHO 2011a)
Production region for which
data was available
Annual cases predicted
by the model for the
country
Epidemiological records of
V. parahaemolyticus illness
following oyster consumption
Wallis Lake, Australia
91
Two cases in 18 years, two large
outbreaks from other seafood
sources
Orongo Bay, New Zealand
0
None during 1997–2002 from
oysters; several outbreaks from
other seafood sources
Hiroshima Bay, Japan
66
13 during 1998–2004
British Columbia, Canada
186
212 in decade 1997–2006
number of V. parahaemolyticus or the number of pathogenic V. parahaemolyticus
ranges from absence in 25 g to 1,000 CFU or MPN per gram”.
The FAO/WHO risk assessment for V. parahaemolyticus in seafood (FAO/WHO
2011a, b) estimated the risk in four countries for which some data was available:
Japan, New Zealand, Canada and Australia. With the exception of New Zealand,
the model predicted higher levels of illness in other regions than are recorded in the
countries notifications (Table 1.1).
In the FAO/WHO risk assessment, four factors were used to model exposure
(a) level of pathogenic V. parahaemolyticus in oysters at harvest (b) effect of
postharvest handling and processing (c) ability of the organism to multiply to an
infective dose (d) number of pathogenic V. parahaemolyticus consumed. However,
local data for the regions mentioned in Table 1.1 were available only with respect to
amount of oysters harvested, time oysters out of water, air and water temperature.
The relation between temperature and V. parahaemolyticus multiplication in oysters
was based on US data, so also was the proportion of V. parahaemolyticus that are
pathogenic, oyster consumption pattern, and illness under-reporting factor. Some
of the differences observed between the predicted illness and epidemiological data
could be due to variations in the above mentioned factors in the model in different
geographical regions. For example, Eyles et al. (1985) reported that V. parahaemolyticus does not multiply in Sydney rock oysters stored at 30
ı C for 7 days.
Further, in trying to address the CCFH question on risk reduction achieved
when different criteria were applied, the FAO/WHO risk assessment also considered the impact of applying criteria on product rejection. This indicated that
application of 100 CFU/g of V. parahaemolytucs criterion would reduce predicted
illness by 96–99 % in Australia, New Zealand and Japan, but this would lead to
rejection of 67, 53 and 16 % of products in these three countries respectively.
This highlights the relation between application of specified target and baseline
levels of V. parahaemolyticus in oysters in different geographical regions and that
establishment of international limits for V. parahaemolyticus in oysters may have
greater impact on product rejection in some countries.
5
Table 1.1 Predicted and reported illness due to V. parahaemolyticus following consumption
of oysters in selected countries (FAO/WHO 2011a)
Production region for which
data was available
Annual cases predicted
by the model for the
country
Epidemiological records of
V. parahaemolyticus illness
following oyster consumption
Wallis Lake, Australia
91
Two cases in 18 years, two large
outbreaks from other seafood
sources
Orongo Bay, New Zealand
0
None during 1997–2002 from
oysters; several outbreaks from
other seafood sources
Hiroshima Bay, Japan
66
13 during 1998–2004
British Columbia, Canada
186
212 in decade 1997–2006
number of V. parahaemolyticus or the number of pathogenic V. parahaemolyticus
ranges from absence in 25 g to 1,000 CFU or MPN per gram”.
The FAO/WHO risk assessment for V. parahaemolyticus in seafood (FAO/WHO
2011a, b) estimated the risk in four countries for which some data was available:
Japan, New Zealand, Canada and Australia. With the exception of New Zealand,
the model predicted higher levels of illness in other regions than are recorded in the
countries notifications (Table 1.1).
In the FAO/WHO risk assessment, four factors were used to model exposure
(a) level of pathogenic V. parahaemolyticus in oysters at harvest (b) effect of
postharvest handling and processing (c) ability of the organism to multiply to an
infective dose (d) number of pathogenic V. parahaemolyticus consumed. However,
local data for the regions mentioned in Table 1.1 were available only with respect to
amount of oysters harvested, time oysters out of water, air and water temperature.
The relation between temperature and V. parahaemolyticus multiplication in oysters
was based on US data, so also was the proportion of V. parahaemolyticus that are
pathogenic, oyster consumption pattern, and illness under-reporting factor. Some
of the differences observed between the predicted illness and epidemiological data
could be due to variations in the above mentioned factors in the model in different
geographical regions. For example, Eyles et al. (1985) reported that V. parahaemolyticus does not multiply in Sydney rock oysters stored at 30
ı C for 7 days.
Further, in trying to address the CCFH question on risk reduction achieved
when different criteria were applied, the FAO/WHO risk assessment also considered the impact of applying criteria on product rejection. This indicated that
application of 100 CFU/g of V. parahaemolytucs criterion would reduce predicted
illness by 96–99 % in Australia, New Zealand and Japan, but this would lead to
rejection of 67, 53 and 16 % of products in these three countries respectively.
This highlights the relation between application of specified target and baseline
levels of V. parahaemolyticus in oysters in different geographical regions and that
establishment of international limits for V. parahaemolyticus in oysters may have
greater impact on product rejection in some countries.