EPI Update, September 9 2005

Weekly newsletter for Center For Acute Disease Epidemiology of Iowa Department of Public Health

Health Transfers: An Application of Health-Health Analysis to Assess Food Safety Regulations

The authors apply a Health-Health Analysis to risks associated with harvesting Gulf oysters to evaluate that approach to managing health and safety risks

The Demand for Eastern Oysters, Crassostrea virginica, from the Gulf of Mexico in the Presence of Vibrio vulnificus

California, in response to health concerns, initiated a program on 1 March 1991 which required anyone selling eastern oysters, Crassostrea virginica, from the Gulf of Mexico area to notify potential consumers that there was a risk in consuming them raw. This mandatory warning, followed shortly thereafter by a similar warning in other states, including Louisiana and Florida, received extensive press cover-age throughout the country and particularly in the Gulf area. This paper examines the extent to which the demand for Gulf-area oysters has been reduced as a result of mandatory warning labels and negative publicity. In general, the results suggest that since 1991 the “summer” dockside price has been reduced by about 50% as a result of warning labels and associated negative publicity, while the “winter” dockside price has been reduced by about 30%

Oyster Demand Adjustments to Counter-Information and Source Treatments in Response to Vibrio vulnificus

A web-based contingent behavior analysis was developed to quantify the effect of both negative and positive information treatments and post harvest processes on demand for oysters. Results from a panel model indicate that consumers of raw and cooked oysters behave differently after news of an oyster-related human mortality. While cooked oyster consumers take precautionary measures against risk, raw oyster consumers exhibit optimistic bias and increase their consumption level. Further, by varying the source of a counter-information treatment, we find that source credibility impacts behavior. Oyster consumers, and in particular, raw oyster consumers, are most responsive to information provided by a not-for- profit, nongovernmental organization. Finally, post harvest processing of oysters has no impact on demand.consumer behavior, information treatments, non-market valuation, optimistic bias, Oyster demand, source credibility, Vibrio vulnificus, Agribusiness, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics, Q18, Q13, Q58,

Specific discrimination of three pathogenic salmonella enterica subsp enterica serotypes using CarB-based oligonuceotide microarray

It is important to rapidly and selectively detect and analyze pathogenic Salmonella enterica subsp. enterica in contaminated food to reduce the morbidity and mortality of Salmonella infection and to guarantee food safety. In the present work, we developed an oligonucleotide microarray containing duplicate specific capture probes based on the carB gene, which encodes the carbamoyl phosphate synthetase large subunit, as a competent biomarker evaluated by genetic analysis to selectively and efficiently detect and discriminate three S. enterica subsp. enterica serotypes: Choleraesuis, Enteritidis, and Typhimurium. Using the developed microarray system, three serotype targets were successfully analyzed in a range as low as 1.6 to 3.1 nM and were specifically discriminated from each other without nonspecific signals. In addition, the constructed microarray did not have cross-reactivity with other common pathogenic bacteria and even enabled the clear discrimination of the target Salmonella serotype from a bacterial mixture. Therefore, these results demonstrated that our novel carB-based oligonucleotide microarray can be used as an effective and specific detection system for S. enterica subsp. enterica serotypes.open117Nsciescopu

Comparative Microbial Dynamics in Crassostrea virginica and Crassostrea ariakensis

Considerations to introduce the Suminoe or Asian oyster Crassostrea ariakensis along the East Coast have raised many questions regarding ecology, economics, and human health. To date, research has focused primarily on the ecological and socioeconomic implications of this initiative, yet few studies have assessed its potential impact on public health. Our work compares the rates of bioaccumulation, depuration and post harvest decay of indicator organisms (such as E. coli) and Vibrio sp. between Crassostrea virginica and Crassostrea ariakensis in the laboratory. Preliminary results suggest that the rates of bioaccumulation of E. coli in Crassostrea ariakensis were significantly lower than those for Crassostrea virginica, depuration of E. coli was variable between the two species, and Crassostrea ariakensis post harvest decay rates of Vibrio sp. were significantly lower than Crassostrea virginica. This research provides coastal managers with insight into the response of Crassostrea ariakensis to bacteria, an important consideration for determining appropriate management strategies for this species. Further field-based studies will be necessary to elucidate the mechanisms responsible for the differences in rates of bioaccumulation and depuration. (PDF contains 40 pages

An Analysis of US Oyster Demand and the Influence of Labeling Requirements

In response to concerns about the morbidity rate associated with the consumption of raw Gulf of Mexico oysters, California initiated a program in March 1991 that required anyone selling raw Gulf oysters to notify potential consumers that the “consumption of raw oysters can cause serious illness and death among people with liver disease, chronic illness, or weakened immune systems.†This labeling requirement, followed shortly thereafter by similar requirements in other states, received extensive media coverage. The primary objective of this study was to consider, within the context of a complete demand system, the impact of mandatory warning labels and associated media attention on the demand for the product subject to regulation and media attention (i.e., Gulf product) as well as substitute products. Results indicate that warning labels lowered the demand for oysters originating from the Gulf and Chesapeake and increased demand for oysters originating from the Pacific and foreign sources. Results also indicate that the own-price flexibilities from all sources are inelastic and, with few exceptions, all products are gross substitutes for one another.Demand analysis, oysters, warning labels, food safety event, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Research Methods/ Statistical Methods, Q18, Q58,

EXPLORATION OF BACTERIA Symbionts Mangrove Waste FOR THE PRODUCTION OF DECOMPOSTER

Mangrove waste comprises of naturally decomposed dead mangrove leaves, twigs, and branches. This research aims to determine the types of bacterial symbionts in mangrove waste with potency as anti-bacterial agents. These anti-bacterial agents will subsequently be used in the production of compost with bio-activators. The research process involves isolation of symbiont bacteria, identification for symbiont bacteria with potency as anti-bacterial agent, DNA extraction using High Pure PCR Temperature Preparation Kit (Roche), DNA amplification by PCR 16s rDNA, and DNA Sequencing. Resulting amplified 16S rDNA are analyzed and then sequenced using Genetix program. Symbionts with identified anti-bacterial properties are used in bio-activator production. Samples of Sargassum seaweed are treated separately with resulting bio-activator product from the research and other bio-activator products for nutritional content comparison. Four types of symbiont bacteria are identified as potential anti-bacterial agents, namely Pseudomonas sp., Flavobacterium sp., Acinetobacter sp., Bacillus subtilis. It is further found that bio-activator products from mangrove waste have better quality compared to those found in the market and non-bio activator added liquid organic fertilizers. Therefore, bio-activators from mangrove waste is a potential alternative as natural bio-activator product