The Vibrio vulnificus bacterium belongs to the vibrionaceae, which also includes vibrio parahaemolyticus and cholera vibrio. Vibrio vulnificus is a gram-negative bacillus that has many points in common with vibrio parahaemolyticus including their characteristics.
Vibrio vulnificus (V. vulnificus) is a bacterium named such due to the fact that this virus causes wounds (vulnus). Living in warm seawater, it multiplies while attaching to the surfaces of crustaceans, fish and shellfish, and animal plankton, and sometimes leaving them for nearby seawater. It multiplies well in a salinity concentration of 2-3% and people are infected by ingesting contaminated fish and shellfish, or through open wounds in their skin. Those who have hepatic diseases, diabetes, and alcoholic hepatitis are likely to be infected. In general, healthy persons are not infected.
In Japan high risk occurs due to ingestion of fish and shellfish used for sashimi and sushi., therefore, those who have high risks of infection due to liver disorders should avoid eating raw fish and shellfish. In Europe and America, on the other hand, the main causes are through ingesting raw oysters.
Healthy persons may experience diarrhea and stomachaches but the symptoms are rarely severe.
However, those who have lowered or compromised immune system conditions, especially patients with severe liver diseases including hepatic cirrhosis, and those who are taking iron drugs due to iron-deficiency anemia should be careful.
Lowered clearance in the liver and serum iron raise the pathogenicity and proliferation of the bacteria. Due to this, after an incubation period of several hours to two days after intrusion of the bacteria into the blood, skin lesions such as cellulitis broaden, and symptoms similar to those of septicemia occur, including fever, chillness and lowered blood pressure. The fatality rate for patients in the case of septicemia is 50% or more.
In the United States, mainly in the states along the Gulf of Mexico, more than 300 cases were reported from 1988 to 1995. In Japan, more than 100 cases have so far been recognized and reported.
Key points to prevention:
1. High risk persons should immediately have medical examinations if they feel ill after eating raw fish and shellfish.
2. Persons who have high risks from this infection due to liver disorders should not eat raw or insufficiently heated crustaceans, fish or shellfish, especially in summer.
- Shellfish should be boiled for five minutes or more after they open, or steamed for nine minutes or more.
- Do not eat closed shellfish.
- Oysters with shells should be boiled for three minutes or more.
3. Be cautious not to allow cooked foods to be exposed to secondary contamination via cutting boards and other cooking tools.
4. Eat foods immediately after cooking.
5. If you have an open wound, take measures to prevent warm seawater and dirty water from entering to the wound.
(There were some cases where people walking barefoot on sandy or rocky beaches were possibly infected because they stepped on seashells and were wounded. Therefore, high risk persons must not walk barefoot on beaches.)