Quantitative Risk Assessment Of Shellfish On Retail From Major Coastal Cities In China

V. parahaemolyticus(Vp) is one of the most important foodborne pathogens in our country and can cause acute gastroenteritis in most cases or blood poisoning in few of cases. At present, the foodborne diseases caused by Vp were gradually increasing year by year especially in littoral areas where outbreak frequency are significantly higher and cases involved in are more than the other areas. In this paper, PCR targeted at tlh and tdh which had been established by previous experiment were used to replace a series of biochemical identification test in MPN quantitative method in national standards. With this method, Vp in shellfish on retail from nine cities were surveyed and estimated. The concentration of Vp in shellfish on retail from nine cities nationwide was investigated, and data on dietary intake of shellfish in Qingdao were surveyed and statistically analyzed. Vp human exposure assessment was performed. The primary research on quantitative assessment on shellfish from nine cities were carried out according to the theory and technology of the microorganism quantitative assessment. The probability of gastroenteritis per meal in different seasons for consumer in nine cities were assessed.In this paper,22 strains with tlh gene detected by PCR were identified by biochemical test to vertify the specificity and accuracy of PCR. The result showed 22 strains with tlh were Vp, which has demonstrated PCR can replace a series of biochemical identification test in MPN to quantify Vp in seafood.Under consideration of the production according to fishery statistics yearbook in 2007, Aquatic products wholesale market in Qingdao, Yantai, Rizhao, Weihai, Lianyungang, Dalian, Guangdong, Xiamen and Zhoushan were chosen to sample shellfish from Oct.2008 to Sep.2009, with total samples 675. Clam, Oyster, Mussel, Razor, Bloody clam, Scallop were major species used in this paper. Background data on concentration of shellfish on retail from nine cities were acquired and analyzed by SPSS to review the distribution patterns of Vp. Vp were widely distributed in shellfish with the average detection rate within the range from 56% to 73.3%,56% shellfish from Rizhao were Vp-positive and 59.7% from Dalian. More than 60% of shellfish from the other seven cities were vp-positive with Lianyungang 73.3%, which was the highest rate in nine cities; The geometric mean concentration of Vp in razor from Qingdao, Yantai and Weihai were 86.6MPN/g,258.4MPN/g and 494.6 MPN/g respectively, which were significantly higher than the other kinds of shellfish (P<0.05). The detection rate (12/12) and geometric mean concentration (269.8MPN/g) of Vp in mussel from Guangzhou significantly higher than the other kinds of shellfish (P<0.05), which suggested that mussel and razor in these cities should be monitored. While the distribution of Vp in shellfish from Rizhao, Dalian, Lianyungang, Xiamen and Zhoushan were similar(P>0.05);The distribution of Vp in shellfish in spring(3-6) and summer(7-9) show no differences among different cities, while Vp distribution in autumn(10-12) and winter(1-3) were significantly different among nine cities with the highest concentration of Vp in shellfish from Zhoushan and lowest concentration of Vp in shellfish from Rizhao, and the highest and lowest concentration of Vp in shellfish in winter were from Guangzhou and Qingdao respectively.0.96% of shellfish were detected Vp with tdh gene in nine cities.By use of the theory on microorganism risk assessment, the quantitative assessment on shellfish on retail from nine cities in our country were carried out.The starting point of exposure assessment was shellfish on retail, the distribution of total Vp, the rate of pathogenic Vp and simple diet survey data were used to assess the exposure, and the temperature in different seasons, the stroge time on retail and the growth rate of Vp were added in exposure model. So the exposure per meal distribution of pathogenic Vp were acquired by using Crystal Ball. The result showed that the exposure in nine cities were highest in summer, within the range from 3.26～5.32. The exposure was lowest in Dalian, with the average exposure was 3.26, and 50 percentile,90 percentile and 97.5 percentile were 3.04,6.95 and 7.91, respectively. The average exposure in Guangzhou was 3.26, and 50 percentile,90 percentile and 97.5 percentile were 3.04,6.95 and 7.91, respectively, which was highest in nine cities. In winter, the exposure was lowest in four seasons, within the range from 0.01 to 2.26, with the highest in Guangzhou, and lowest in Qingdao.The distribution of probability of gastroenteritis per meal by consuming pathogenic Vp of consumer in nine cities were acquired by quantitative assessment, which showed the high risk of raw-consuming shellfish. In summer, the average probability of gastroenteritis per meal for people in Qingdao was 3.41E-03,50 percentile,90 percentile and 97.5 percentile were 2.31E-03,7.79E-01 and 9.18E-01, comparing with actual morbidity statistics from 2004 which showed the probability of gastroenteritis induced by Vp was 5.58E-5, lower than the result acquired in this paper. There were a lot of missing data druing the epidemiological survey, so actual cases were more than the cases acquired.