Shellfish Quality Resource: Safety

Vibrio parahaemolyticus (Vp) is a naturally occurring marine bacterium found worldwide and is often associated with food poisoning incidences relating to seafood products. Both pathogenic and non-pathogenic forms of the organism can be isolated from marine and estuarine environments and from fish and shellfish dwelling in these environments. Warm summer temperatures and estuarine conditions (reduced ocean salinity) are favourable for growth of this species. Increased levels may be treated as an environmental event and presence of the bacteria in seawater and shellstock is not related to pollution or sewage and levels decrease when water temperatures cool. Growth rates are directly related to temperature and the bacterium is rarely found when water temperatures are less than 15^o Celsius.

More serious forms of vibrio include Vibrio cholera associated with unsafe drinking water and Vibrio vulnificus. Vibrio vulnificus is a warm water species predominantly present in the Gulf of Mexico that has been associated with several severe illnesses and fatalities. This is not the species present in the Pacific Northwest. There have never been any reported illnesses associated with Vibrio vulnificus from this region.

Vibrio parahaemolyticus in British Columbia

Vibrio parahaemolyticus is known to exist in waters of the Pacific Northwest but outbreaks have not been recorded in British Columbia until 1997. Outbreaks have been recorded in Washington State as early as 1981. Major outbreaks have occurred in the US during warmer months of the year and sporadic cases occur frequently along all coasts of the US. This is very common in Japan where large outbreaks occur with regularity (usually associated with raw fish).

During July-August 1997, one of the largest reported outbreak in North America of culture-confirmed Vibrio parahaemolyticus infections occurred in North America. In BC there were 101 illnesses confirmed that related to the consumption of raw oysters from BC. Of these illnesses, 23 were related to self-harvest, 23 related to shellfish sales in the retail sector and 65 were directly related to restaurants. As a result, the BC Centre for Disease Control (BCCDC) issued a consumer advisory to cook all shellfish prior to consumption.

Following this outbreak in BC, illness data and environmental monitoring of Vibrio parahaemolyticus levels indicated temporal (time) and geographic variation, with the high-risk period in the months of July and August, and the highest risk areas in BC being the waters of the Southern Straight of Georgia (DFO Statistical areas 13 through 19). Data collected through CFIA monitoring of environmental Vp levels in oysters showed that elevated levels of Vp were not found in oysters where meat temperatures at the time of harvest did not exceed 14^oCelsius.

Health risks and illness associated with Vibrio parahaemolyticus

Vibrio parahaemolyticus has a remarkable capacity for growth and levels can double as fast as 12 to 18 minutes in seafood and as fast as 8 to 9 minutes at 37^o Celsius. Moderate levels of the bacteria (100’s/gram) can increase to high levels in as short as 2 - 3 hrs if product reaches 20 - 35 ^o Celsius. Because of its rapid growth rate, temperature control of products to prevent growth of the bacteria is critical to product safety. Cooling product after abuse will only slow reproduction and refrigeration cannot be relied upon to kill the bacteria. Vp will persist in frozen seafood for a long period.

Raw, mishandled, improperly stored or cross contaminated cooled seafood are generally the source of illness with shrimp, crab, lobster and oysters producing the most incidences in North America. Levels of the bacterium in food are reported in “organisms per gram”. This bacterium is unable to grow at temperatures below 12^o Celsius and is easily destroyed by cooking temperatures.

The USFDA has set action levels for harvesting closure at 10,000/gram. However, this action level is currently under review, as recent data seems to indicate that illnesses may occur at lower levels, likely depending on the specific Vp strains involved.

Consumption of large numbers of Vibrio parahaemolyticus causes vibriosis or gastroenteritis, symptoms may be severe and include nausea, diarrhea and in some individuals abdominal cramps and fever. The incubation period from consumption to illness may range between 4 to 96 hours and recovery may take as long as a week. The disease is caused when the bacterium attaches itself to the small intestine and secretes an unidentified toxin. The disease usually runs its course in 2 - 3 days although some cases may require hospitalization or antibiotic treatment. Severe disease is rare and occurs more commonly in persons with weakened immune systems. V. parahaemolyticus can also cause an infection of the skin when an open wound is exposed to warm seawater. Raw or undercooked oysters and clams will put consumers at risk. Cooking seafood to more than 65^o Celsius (145 degrees Fahrenheit) may effectively destroy the bacteria. Cooked seafood should be eaten within 2 hours of preparation or promptly chilled to less than 5^o Celsius and held in refrigeration.

Vp Advisory Committee & Risk Reduction Strategy

Given the serious nature of the situation, a committee was established to review the data, understand the Vp organism in more detail and determine appropriate controls. The committee was comprised of Provincial and Municipal Health Authorities, Industry, the BC Restaurant Association and the Canadian Food Inspection Agency (CFIA). This committee worked together in the development and refinement of a Vp Risk Reduction Strategy (RRS) to help prevent further outbreaks of Vp associated with consumption of raw oysters. The RRS included control of oysters from harvest, prompt reporting and investigation of illnesses, a communications strategy, and a tiered action plan that addressed Vp levels, illnesses and time of year.

As part of the Vp Risk Reduction Strategy, CFIA initiated a monitoring program of BC oysters in 1997. Since 1997, this program has continued and runs from May – September every year. The Vp monitoring samples indicate the Vp levels in the shellfish and signal when extra precautionary measures need to be taken.

Vp Management

Preventing contamination and potential illnesses due to Vp are critical to the shellfish culture industry. Each publicized illness has significant impacts on shellfish markets and if illnesses cannot be prevented the industry will be faced with summer restrictions on sales. Prevention of V. parahaemolyticus hazards can be achieved through a variety of means, most of which require extension of controls to the harvest level. During this summer participation in the Vibrio control program will be mandatory for growers who wish to maintain shellfish sales during July and August, as CFIA will require all shellfish processors to implement Vp controls at the harvest site.

BCSGA Vp Control Program

Introduction

In the summer of 2000, the BC Shellfish Growers Association, in conjunction with the Canadian Food Inspection Agency and the BC Ministry of Agriculture, Food and Fisheries, developed a Vibrio parahaemolyticus (Vp) control program to minimize possible threats of increased levels of Vp in shellfish cultured in BC and possible related consumer illnesses. This program involved the use of strict time temperature control matrices for shipment during summer months and the use of a HACCP style Bill of Lading form that accompanied all shellfish shipments. Kingzett Professional Services Ltd. (now Blue Revolution Consulting Group developemd the bill of lading that is now in use on behalf of the BCSGA.

In preparation for the upcoming high Vp risk summer months of July and August, CFIA, jointly with the BC Shellfish Growers Association, organized and conducted a Vp workshop to share the latest information on Vp and to further refine the Vp control plan and the Vp Bill of Lading form for 2002. All BC processors and growers were invited to attend the workshop.

The workshop provided participants with an update of the latest findings and research on Vp, as well as provided an opportunity for the discussion of effective temperature control /risk reduction strategies. In addition, participants provided feedback as to the effectiveness of the of the Vp Bill of Lading form.