Pathogens 101 | Vibrio

What is Vibrio?

Vibrio parahaemolyticus bacterium is in the same family as those that cause cholera. It lives in brackish saltwater and causes gastrointestinal illness in humans. Vibrio naturally inhabits coastal waters in the United States and Canada and is present in higher concentrations during summer. Learn more!

What type of illness is caused by Vibrio?
When ingested, Vibrio 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.

Vibrio infection
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 is Vibrio infection diagnosed?
Vibrio organisms can be isolated from cultures of stool, wound, or blood. 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 Vibrio infection if a patient has watery diarrhea and has eaten raw or undercooked seafood, especially oysters.

Treating Vibrio
Treatment is not necessary in most cases of Vibrio 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 ciprofloxacin can be used. The choice of antibiotics should be based on antimicrobial susceptibilities of the organism.

How common is infection with Vibrio?
An estimated 4500 cases of Vibrio 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. 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 do oysters get contaminated with Vibrio?
Vibriois a naturally occurring organism commonly found in waters where oysters are cultivated. When the appropriate conditions occur with regard to salt content and temperature, Vibrio thrives.

How is Vibrio infection prevented?
Most infections caused by Vibrio in the United States can be prevented by thoroughly cooking seafood, especially oysters. When an outbreak is traced to an oyster bed, health officials recommend closing the oyster bed until conditions are less favorable for Vibrio.

Timely, voluntary reporting of Vibrio 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 Vibrio.

What can I do to prevent poisoning by marine toxins?

General guidelines for safe seafood consumption:

  1. Although any person eating fish or shellfish containing toxin or disease-causing bacteria may become ill, persons with weakened immune systems or liver problems should not eat raw seafood because of their higher risk of Vibrio infection.
  2. Keep seafood on ice or refrigerated at less than 38° Fahrenheit to prevent spoilage.

Specific advice for avoiding marine toxin poisoning:

  1. Keep fresh tuna, mackerel, grouper, and mahi mahi refrigerated to prevent development of histamine. Don’t believe that cooking spoiled or toxic seafood will keep you safe. These toxins are not destroyed by cooking.
  2. Do not eat barracuda, especially, those from the Caribbean.
  3. Check with local health officials before collecting shellfish, and look for Health Department advisories about algal blooms, dinoflagellate growth or “redtide” conditions that may be posted at fishing supply stores.
  4. Do not eat finfish or shellfish sold as bait. Bait products do not need to meet the same food safety regulations as seafood for human consumption.

What are marine toxins?
Marine toxins are naturally occurring chemicals that can contaminate certain seafood. The seafood contaminated with these chemicals frequently looks, smells, and tastes normal. When humans eat such seafood, disease can result.

What sort of diseases do marine toxins cause?
The most common diseases caused by marine toxins in United States in order of incidence are scombrotoxic fish poisoning, ciguatera poisoning, paralytic shellfish poisoning, neurotoxic shellfish poisoning and amnesic shellfish poisoning.


Photo courtesy of CDC/James Archer

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