What is Vibrio parahaemolyticus?
Vibrio parahaemolyticus is a bacterium in the same family as those that cause cholera and Vibrio vulnificus. It lives in brackish saltwater and causes gastrointestinal illness in humans. V. parahaemolyticus naturally inhabits coastal waters in the United States and Canada and is present in higher concentrations during summer; it is a halophilic, or salt-requiring organism.
What type of illness is caused by V. parahaemolyticus?
When ingested, V. parahaemolyticus causes watery diarrhea often with abdominal cramping, nausea, vomiting, fever and chills. Usually these symptoms occur within 24 hours of ingestion. Illness is usually self-limited and lasts 3 days. 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.
How does infection with V. parahaemolyticus occur?
Most people become infected by eating raw or undercooked shellfish, particularly oysters. Less commonly, this organism can cause an infection in the skin when an open wound is exposed to warm seawater.
How common is infection with V. parahaemolyticus?
An estimated 4500 cases of V. parahaemolyticus infection occur each year in the United States. However, the number of cases reported to CDC is much lower because surveillance is complicated by underreporting. Laboratories rarely use the selective medium that is necessary to identify this organism, and it is likely that many cases are undetected. To improve our ability to monitor trends, infections caused by V. parahaemolyticus and other Vibrio species became nationally notifiable in 2007. State health departments report cases to CDC, and these reports are summarized annually.
How is V. parahaemolyticus infection diagnosed?
Vibrio organisms can be isolated from cultures of stool, wound, or blood. For isolation from stool, use of a selective medium that has thiosulfate, citrate, bile salts, and sucrose (TCBS agar) is recommended. If there is clinical suspicion for infection with this organism, the microbiology laboratory should be notified so that they will perform cultures using this medium. A physician should suspect V. parahaemolyticus infection if a patient has watery diarrhea and has eaten raw or undercooked seafood, especially oysters, or when a wound infection occurs after exposure to seawater.
How is V. parahaemolyticus treated?
Treatment is not necessary in most cases of V. parahaemolyticus infection. There is no evidence that antibiotic treatment decreases the severity or the length of the illness. Patients should drink plenty of liquids to replace fluids lost through diarrhea. In severe or prolonged illnesses, antibiotics such as tetracycline or ciprofloxicin can be used. The choice of antibiotics should be based on antimicrobial susceptibilities of the organism.
How do oysters get contaminated with V. parahaemolyticus?
Vibrio is a naturally occurring organism commonly found in waters where oysters are cultivated. When the appropriate conditions occur with regard to salt content and temperature, V. parahaemolyticus thrives.
How is V. parahaemolyticus infection prevented?
Most infections caused by V. parahaemolyticus in the United States can be prevented by thoroughly cooking seafood, especially oysters. Wound infections can be prevented by avoiding exposure of open wounds to warm seawater. When an outbreak is traced to an oyster bed, health officials recommend closing the oyster bed until conditions are less favorable for V. parahaemolyticus.
Timely, voluntary reporting of V. parahaemolyticus infections to state health departments and to regional offices of the Food and Drug Administration (FDA) will help collaborative efforts to improve investigation of these infections. Regional FDA specialists with expert knowledge about shellfish assist state officials with tracebacks of shellfish. When notified rapidly about cases, officials can sample harvest waters to discover possible sources of infection and may close oyster beds. Ongoing research may help us to predict environmental or other factors that increase the chance that oysters carry Vibrios.
How can I learn more about Vibrio parahaemolyticus?
You can discuss medical concerns with your doctor or other health care provider. Your local health department can provide information about this and other public health problems. Information about problems associated with raw seafood consumption can be obtained from the FDA’s Center for Food Safety and Applied Nutrition (telephone 1-800-332-4010). At this number recorded information is available on many subjects including seafood consumption and handling. A public affairs specialist is available 12:00 p.m.-4:00 p.m. Eastern Standard Time. Seafood safety information is also available on the world wide web at http://vm.cfsan.fda.gov and http://seafood.ucdavis.edu.
Watery diarrhea, often with abdominal cramping, nausea, vomiting, and fever. Less commonly, wound or soft tissue infections. Occasionally bloodstream infections.
Vibrio parahaemolyticus, a halophilic (salt-requiring) gram- negative bacterium naturally and commonly found in warm marine and estuarine environments.
Nationwide, an average of 215 culture-confirmed cases, 30 hospitalizations, and 1-2 deaths are reported each year. However, it is estimated that there are truly as many as 4500 cases (most not culture confirmed).
Most persons recover after 3 days and suffer no long-term consequences. Bloodstream infections and death are uncommon and usually occur in persons with underlying medical conditions.
Eating raw or undercooked shellfish, particularly oysters. Less commonly, wound infections may occur when wounds or soft tissues are exposed to warm seawater.
All persons. Persons with underlying medical conditions, such as alcoholism and liver disease may be at increased risk of infection and serious complications.
Surveillance for infections has been conducted in the Gulf Coast states of Alabama, Florida, Louisiana, Mississippi, and Texas since 1988, and expanded to include FoodNet sites in 1996. In January 2007, infections caused by V. parahaemolyticus and other Vibrio spp. became nationally notifiable. Thirty-three states have now implemented this reporting to state public health officials and CDC.
Infections are seasonal; approximately 70% occur between May and October when water temperatures are warmer. Large outbreaks linked to the consumption of raw oysters occurred in 1997, 1998, and 2006. Environmental factors, such as warm water and moderate salinity, can increase the number of V. parahaemolyticus organisms in shellfish.
Many persons prefer to consume oysters and other shellfish raw. Not all strains cause illness. Large outbreaks have occurred when counts of V. parahaemolyticus in oysters from implicated sites were very low. Therefore, monitoring and responding to elevated counts of V. parahaemolyticus in the harvesting waters and in shellfish does not adequately protect the public health.
Education focusing on the risks associated with consumption of raw and undercooked shellfish, especially in warm months. Implement refrigeration from harvesting to consumption. Revision of the standards used for closing and re-opening of oyster beds to take into account the role of environmental factors.
CDC Surveillance Reports
Cholera and Other Vibrio Illnesses Surveillance (COVIS): These surveillance summaries provide a national picture of the occurrence of several species of Vibrio illnesses.
- Cholera and Other Vibrio Illness Surveillance (COVIS) Overview [PDF - 3 pages]
Foodborne Diseases Active Surveillance Network (FoodNet): These surveillance reports provide the information necessary for measuring the progress in foodborne disease prevention. Foodnet tracks laboratory-confirmed data about several species of Vibrio and other foodborne infections in 10 surveillance sites. FoodNet sites also report Vibrio infections to COVIS.
Select MMWR Articles
- CDC. Vibrio parahaemolyticus infections associated with consumption of raw shellfish—Three states, 2006. MMWR;55:854-6.
- CDC. Outbreak of Vibrio parahaemolyticus infection associated with eating raw oysters and clams harvested from Long Island Sound - Connecticut, New Jersey, and New York, 1998. MMWR 1999;48:48-51.
- CDC. Outbreak of Vibrio parahaemolyticus infections associated with eating raw oysters - Pacific Northwest, 1997. MMWR 1998;47:457-462.
Select CDC References
- Baker-Austin C. Spread of Pacific Northwest Vibrio parahaemolyticus Strain [correspondence letter]. N Engl J Med 2013; 369:1573-1574.
- Newton A, Kendall M, Vugia, DJ, Henao O, Mahon B. Increasing Rates of Vibriosis in the United States, 1996–2010: Review of Surveillance Data From 2 Systems. Clin Infect Dis. 2012; 54 (suppl 5): S391-S395
- McLaughlin JB, DePaola A, Bopp CA, et al. Outbreak of V. parahaemolyticus gastroenteritis associated with Alaskan oysters. N Engl J Med 2005;353:1463-70.
- Hlady WG, Klontz KC. The epidemiology of Vibrio infections in Florida, 1981-1993. J Infect Dis 1996;173:1176-1183.
- Levine WC, Griffin PM, Gulf Coast Vibrio Working Group. Vibrio infections on the Gulf Coast: results of the first year of regional surveillance. J Infect Dis 1992;167:479-83.
- Desenclos JCA, Klontz KC, Wolfe LE, Hoecherl S. The risk of Vibrio illness in the Florida raw oyster eating population, 1981-1988. Am J Epidemiol 1991;134:290-7.
- Daniels NA, Ray B, Easton A, et al. Emergence of a new Vibrio parahaemolyticus serotype in raw oysters. A prevention quandary. JAMA 2000; 284: 1541-1545.
- Daniels NA, MacKinnon L, Bishop R, Altekruse S, Ray B, Hammond RM, Thompson S, Wilson S, Bean NH, Griffin PM, Slutsker L. Vibrio parahaemolyticus Infections in the United States, 1973-1998. J Infect Dis 2000; 181: 1661-1666.
- Daniels NA, Evans MC, Griffin PM. Noncholera Vibrios. Chapter 10, Emerging Infections 4, ASM Press, Washington, D.C., 2000.
Related Web Sites
- Enteric Diseases Epidemiology Branch
- CDC National Surveillance Team
- CDC Features: includes information about Vibrio illness
- Digital Press Kit: New Food Safety Data for 2012
- CDC and Food Safety