Vibrio

Vibrio

Vibrio species account for a significant number of foodborne infections from the consumption of raw or undercooked shellfish. They require salt to grow, and are thus associated with ocean-sourced seafood. There are four Vibrio species of primary public health concern: Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio cholerae O1 and Vibrio cholerae non-O1.

WHAT IS VIBRIO?

Vibrio species account for a significant number of foodborne infections from the consumption of raw or undercooked shellfish. They require salt to grow, and are thus associated with ocean-sourced seafood. There are four Vibrio species of primary public health concern: Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio cholerae O1 and Vibrio cholerae non-O1.

Vibrio vulnificus is found in most coastal waters, primarily in estuaries where the tide flows in to a river causing fresh and salt water to mix. It is associated with plankton, shellfish and finfish. It is considered the most serious pathogenic Vibrio in industrialized nations.

Vibrio parahaemolyticus is also found in coastal water estuarine environments. It is associated with marine fish and shellfish.

Vibrio cholerae O1 causes Asiatic or epidemic cholera. This organism may be found in the temperate estuarine and marine coastal areas. Cholera occurs in developing nations; periodic epidemics can spread quickly in developing countries around the world often linked to contaminated drinking water. Sporadic cases occur periodically in industrialized nations.

Vibrio cholerae non-O1 infects only humans and other primates and has genetic differences from the "O1" strain. Non-O1 strains cause a less severe disease. Pathogenic and nonpathogenic strains of the organism are found in marine and estuarine environments.

WHAT ARE THE SYMPTOMS?

If immunocompromised people or those with impaired liver function consume seafood contaminated with even low levels of Vibrio vulnificus, a severe blood infection (septicemia) can occur. The microorganism enters the blood stream, causing septic shock, which is rapidly followed by death in many cases (about 50 percent). More than 70 percent of infected individuals have distinctive bulbous skin lesions. Consumption of contaminated seafood by healthy people can result in vomiting, diarrhea and abdominal pain. Symptoms begin around 38 hours after consumption of contaminated food, and the disease progresses rapidly.

Vibrio parahaemolyticus causes mild or moderate gastroenteritis with symptoms of diarrhea, abdominal cramps, nausea, vomiting, headache, fever and chills. The illness persists for about 2.5 days after an incubation period of four to 96 hours after ingestion. A Food and Drug Administration risk assessment determined that 15 percent of oyster associated illnesses are caused by servings at or above 10,000/g at the time of harvest.

Vibrio cholerae O1 causes a mild or acute watery diarrhea. Onset is usually sudden, with incubation periods varying from six hours to five days. Symptoms include abdominal cramps, nausea, vomiting, dehydration and shock. Death may occur after severe fluid and electrolyte loss. Illness is caused when viable bacteria attach to the small intestine and produce cholera toxin. It is believed that the infectious dose is likely greater than one million organisms.

Vibrio cholerae non-O1 causes a gastroenteritis by the same name. Symptoms include diarrhea, abdominal cramps and fever, with vomiting and nausea occurring in approximately 25 percent of infected individuals. Approximately 25 percent of infected individuals will have blood and mucus in their stools. Diarrhea may last six to seven days and will usually occur within 48 hours after ingestion of the organism. The infective dose is suspected to be more than one million organisms. Although rare, septicemia, as has been reported with V. vulnificus, has been reported and deaths have resulted.

HOW IS IT TRANSMITTED?

Vibrio vulnificus has been isolated from oysters, clams and crabs. Consumption of these raw or re-contaminated products may result in illness. Wound infections may result either from Vibrio-containing sea water contamination of an open wound, or by cutting part of the body on an underwater sharp object (coral, fish, etc.), followed by contamination with the organism. There is no evidence of person-to-person transmission of V. vulnificus.

Vibrio parahaemolyticus has been associated with consumption of raw, improperly cooked, or cooked and re-contaminated fish and shellfish.

Vibrio cholerae O1 is generally spread through contaminated water supplies and by poor sanitation. Sporadic cases occur due to the consumption of raw or improperly cooked shellfish harvested from contaminated coastal waters. Vibrio cholera is part of the indigenous microflora of these waters.

Vibrio cholerae non-O1 is transmitted by consuming raw, improperly cooked, or cooked and re-contaminated shellfish.

HOW IS IT CONTROLLED?

The primary control for Vibrio is harvesting seafood from safe waters. Many countries test coastal waters for safe harvesting. Raw oyster-related outbreaks are more frequent in the summer months and are more prevalent in Gulf Coast waters than in other areas of the United States. Thus, limiting the time of harvest may also be an effective control strategy.

After harvest, seafood should be chilled to less than 5°C (41°F) to prevent growth of Vibrio. Cooking seafood to at least 65°C (149°F) will destroy Vibrio; however, this is not a control strategy for those who choose to consume it raw.

Protection from post-process contamination with raw products is important for cooked products. Cooked seafood should be eaten within two hours or promptly chilled to less than 5°C (41°F).

Growth parameters vary among the three Vibrio species.

Temperature (°C) pH Water activity Salt (percent)
V. cholerae 10 – 43 5 – 9.6 0.97 – 0.998 0.1 – 4
V. parahaemolyticus 5 – 43 4.8 – 11 0.94 – 0.996 0.5 – 10
V. vulnificus 8 – 43 5 – 10 0.96 – 0.997 0.5 – 5

Research at the University of Delaware has shown that the use of high hydrostatic pressure inactivates pathogenic strains of Vibrio.1 High-pressure processing may be advantageous over thermal treatments since pathogens such as Vibrio can be inactivated while virtually all flavor, colour and nutritional constituents are maintained.

 Cholera spread can be limited with attention to hygiene and sanitation and providing access to clean drinking water.  In addition, a short acting vaccine is available and can be deployed to regions at greatest risk or after natural disasters such as floods. 

For assistance with this topic or other food safety questions for your operation, please Contact Us.



REFERENCES AND FURTHER INFORMATION

1Berlin, D.L., Herson, D.S., Hicks, D.T. and Hoover, D.G. Response of Pathogenic Vibrio Species to High Hydrostatic Pressure. Appl Environ Microbiol. 1999 June; 65(6): 2776–2780.