Illnesses caused by Vibrio parahaemolyticus are an economic burden to the oyster industry. We estimated the economic burden in the oyster production chain in Washington State. Results helped contextualize these costs among other burdens, established a model for investigating burdens from other diseases, and laid groundwork for more precise expenditure surveys. Vibrio will likely increase with warming ocean temperatures, so estimating associated costs also helps with future planning and prevent illness.
Why We Care
Bacteria belonging to the genus Vibrio occur naturally in our coastal areas around the globe. However, certain species and strains are capable of causing human illness. In the United States, one species, Vibrio parahaemolyticus (Vp) is responsible for about 45,000 illnesses annually. While normally presenting as self-limiting gastroenteritis, its strong association with consumption of raw oysters is a concern both for human health and the sustainability of a growing halfshell industry.
Washington State is one of the largest oyster producing regions in the country, estimated to add over $270M annually to the state’s Gross Domestic Product. However, it also has one of the highest rates of V. parahaemolyticus illness burden. Because of the historic occurrence of illness, Washington State Department of Health (WDOH) has developed a control plan in accordance with the National Shellfish Sanitation Program (NSSP) that aims to reduce the likelihood of illnesses during periods when Vp illnesses are reasonably likely to occur. In the protection of human health related to Vibrio exposure, the State conducts a large-scale monitoring effort, has dedicated staff devoted to the issue, and a variety of expenses associated with developing control plans and coordinating with the industry and national guidelines.
Illnesses associated with oyster consumption trigger a chain of events in order to trace back the origin of the oyster through the supply chain and the harvest area. Closure of growing areas due to illnesses can create financial hardship, particularly on smaller and tribal operations that only have harvest sites in the affected area. Oyster recalls can occur after harvest area closures erode consumer confidence and likely decrease sales. To reduce the risk of illness and meet control plan requirements, growers, distributors, and retail outlets have invested in equipment or changed harvest strategies, increasing their operating costs.
What We Did
There are three main stakeholder groups that stand to be affected by a Vibrio case or outbreak outside of the health system treating cases: restaurants/retail/consumers, managers, and producers. These sectors each have different responsibilities when responding to Vibrio illnesses and therefore differential impacts, but collectively represent a complex set of impacts with potential to be a large burden on the industry as a whole. First, we further describe whom we mean by each stakeholder group and then describe the mixed method set that will be used to approach such a complex set of stakeholders.
- Restaurants/Retail and Consumers: Oyster consumption where Vibrio is a concern is primarily through the raw market, which is in turn primarily served in restaurants and bars. These businesses serve as an important midpoint between producers and consumers and are impacted by trends and concerns in both of these populations.
- Management: Managers from state and tribal health departments and natural resource departments are responsible for disease monitoring and response to minimize illness risk to the consumer and responding when illnesses, especially outbreaks affecting multiple people, occur. They incur direct costs of operation in requiring disease management strategies.
- Producers: A large proportion of oyster consumption in the Pacific Northwest is from aquaculture, with a variety of farm types. They are responsible for implementing disease control practices and are economically impacted by both Vibrio cases from their own leases, as well as the reputation of the regional industry as a whole.
In order to reach these different stakeholders and verify the information throughout the industry, we used a multi-part mixed methods approach. These methods combined to form a conceptual model and statistical model for how costs associated with Vibrio accrue through the production chain. Our approach involved the following components:
- Workshops with key informants from each of the stakeholder groups to establish the conceptual model for where costs are incurred throughout the system and by whom.
- Informal interviews with restaurant managers, environmental managers, and producers to approximate the direct costs of Vibrio prevention and management after illnesses and/or closures are reported. These interviews approximated the direct costs of Vibrio to the oyster production chain outside of the potentially decreased consumer demand.
- Workshop to refine and contextualize the findings of the statistical analysis based on observations and common practices in the oyster aquaculture industry. This included stakeholders from restaurants, managers, and producers. This tuned our model and determined that it included all appropriate factors in determining the economic burden of Vibrio.
Final products included a journal article in the Journal of Shellfish Research and a report out to the Pacific Shellfish Growers Association annual meeting.
Benefits/Impact of Our Work
We provided the Washington oyster industry and State of Washington with the first evaluation of the economic burden imposed by Vibrio across the whole production chain. The process employed existing data from WDOH and the industry pertaining to bed closures and oyster sales, and new data collected through interviews of consumers, retailers, and growers. These economic burden estimates provided managers and growers a range of expenses to consider for future budgets and reserves for unpredictable costs. It also provided the groundwork for a more specific expenditure survey should stakeholders desire more finely tuned estimates of the various categories costs in our model.