Vibrio cholera illnesses associated with Herring Eggs harvested through spawn-on-kelp in B.C.
In March 2018 a small group of people were confirmed, by lab testing, to have Vibrio cholerae infections. Their illnesses were associated with consumption of herring eggs harvested in the French Creek and Qualicum Bay areas. The same type of Vibrio cholerae bacteria were also found in herring egg and marine water samples.
Herring eggs are an important traditional seafood for many First Nations in B.C., providing cultural, nutritional, and economic benefits. They are an important source of protein, vitamin D, vitamin A, iron, zinc and several other nutrients. The advice below is informed from a detailed review by Health Canada along with guidance from the BC Center for Disease Control on managing seafood-related illnesses.
Vibrio cholerae bacteria:
The illnesses were caused by non-toxigenic Vibrio cholerae non-01/non-0139 bacteria which was found both in ill persons and in herring eggs collected from French Creek and Qualicum Bay. This bacteria does not produce cholerae toxin which is responsible for the well-known severe form of Vibrio cholerae illness. The non-toxigenic form of the bacteria has the following characteristics:
- It is a natural inhabitant of the marine and estuarine environment.
- It is not an indicator of poor sanitation or sewage contamination.
- Infections are relatively rare, but when they occur, include such symptoms as diarrhea, abdominal cramps, fever, vomiting, nausea, blood and mucus of the stool.
- Individuals with less stomach acid (young children, elderly and those taking antacids) and/or with underlying medical conditions (i.e. chronic liver disease, people with a compromised immune system and people with other chronic illnesses) are more at risk.
- Usually the illness is self-limiting and of short duration (less than one week, usually 1-3 days).
- Until 2018, there has been no reported outbreaks associated with this bacteria following the consumption of seafood.
A number of factors affect how Vibrio cholerae bacteria survives and grows in marine environments.
- Environmental conditions, such as nutrient availability, salinity, acidity, temperature, and sunlight.
- Survival strategies that allow for its growth, protection, and persistence, on its own or in association with other marine organisms, such as biofilms, attachment to sediments, and ability to bind to chitin.
- There is evidence suggesting that climate change, including rising temperatures, increases the risk of infections associated with the bacteria.
- The two factors that contribute most to the growth of the bacteria are water temperature above 10⁰C and low salinity seawater.
- At the time of the March 2018 harvest, although water temperatures were below 10⁰C, a relatively high rainfall could have affected different environmental factors, including lowering salinity and increasing nutrient availability.
- Unlike other shellfish monitoring programs that have early warning indicators, there is currently not a single signal or combination of environmental signals that could be monitored to reliably predict the abundance of the bacteria in water.
Time and temperature control are the most important factors affecting the growth of Vibrio bacteria in seafood. Carrying out some key steps before, during, and after harvesting can reduce some of the risks.
- Sanitize totes and equipment used for harvest and storage prior to use with a sanitizing agent. Include any surfaces seafood may come in contact with, such as rakes and surfaces within the vessel.
- Sanitizing options:
- 200 ppm bleach solution: add 17 mL of 5% sodium hypochlorite to 4 litres of water. Refer to the BC FOODSAFE Chlorine Dilution Calculator to calculate any volume http://www.foodsafe.ca/dilution-calculator.html, OR
- 200 ppm peracetic acid OR
- 200 ppm quats (quaternary ammonium) solution OR
- Environmentally safe disinfectant options to avoid introducing chemicals into the environment:
- steam or hot water rinsing, cleaning, and sanitizing at temperatures above 70°C or 160°F OR
- 1% Virkon aquatic solution OR
- Other recognized sanitizers approved by Health Canada for aquatic environments.
- Wash hands with drinking-quality water and soap before handling eggs.
- Where possible, rinse eggs using drinking-quality water or use boiled and cooled salt-water to preserve taste (38 g of salt per litre or two heaping tablespoons in 4 cups is equivalent to sea-water specific gravity of 1.026). Rinsing helps to reduce some of the bacteria that may be present.
- Use ice made with drinking-quality water to keep eggs cold.
- Place harvested eggs immediately on plenty of ice in a cooler or tote to keep product cold (less than 4°C) and minimize time outside of cold storage. This will prevent bacteria from growing.
- Keep harvested eggs cold at all times, including during transportation. Refrigerate or freeze as soon as possible. It is important to avoid delays between harvest and refrigeration.
- Wash hands with drinking-quality water and soap before handling eggs.
- Use drinking-quality water in preparing herring eggs.
- Sanitize equipment and utensils used for handling herring eggs.
- Cook herring eggs to an internal temperature of 63⁰C for at least 15 seconds to destroy bacteria. Blanching herrings eggs in salted boiling drinking-quality water will also reduce bacteria levels: to blanch add eggs to salted-boiling water for 1 minute, remove and add to chilled boiled salted water. If cooking is not preferred, be aware that there is always a risk with eating raw seafood.
- Under refrigerated storage at 4⁰C or lower, seafood will have a shelf-life of 1-3 days.
If you become ill:
If you become ill with any of the following symptoms: diarrhea, abdominal cramps, fever, vomiting, nausea, or blood in the stool after eating herring eggs, you are advised to visit your health care provider. Individuals with less stomach acid (young children, elderly and those taking antacids) and/or with underlying medical conditions (i.e. chronic liver disease, people with a compromised immune system and people with other chronic illnesses) should be particularly aware of these possible symptoms and seek medical care immediately. Usually the illness is self-limiting and of short duration (less than one week, usually 1-3 days).
For immediate help, call the nurse line at 811, or Drug Poison Info Line at 1.800.567.8911
Vibrio cholerae is an emerging issue on the B.C. coast. Health Authorities, federal and provincial agencies and First Nations communities are committed to doing further work to better understand this issue. Further information will be shared as it becomes available.
Want to know more:
Learn more about safe fish and shellfish at http://www.bccdc.ca/health-info/prevention-public-health/fish-shellfish-safety and https://www.canada.ca/en/health-canada/services/meat-poultry-fish-seafood-safety/shellfish-food-safety.html
BCCDC Shellfish Harvesting Sites Status Map to identify if an area is open or closed: http://maps.bccdc.org/shellfish/
Vibrio cholerae infections at https://www.cdc.gov/vibrio/index.html
Find more information on Food Safety for First Nations communities at: http://www.fnha.ca/wellnessContent/Wellness/Healthy_Food_Guidelines_for_First_Nations_Communities.pdf
First Nations People of Canada: Manual for Healthy Practices (Health Canada, 2011) can be ordered here: https://www.canada.ca/en/indigenous-services-canada/services/first-nations-inuit-health/reports-publications/health-promotion/food-safety-first-nations-people-canada-manual.html
First Nations Health Authority