Seafood Safety

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Symptoms & Treatment

Vibrio vulnificus can cause sepsis in individuals who consume contaminated shellfish, and can also cause wound infections in individuals who expose open sores to contaminated water.

Symptoms of septicemia usually begin within 24 - 48 hours of consuming contaminated seafood (Morris and Black, 1985). The most common symptoms include: bullous skin lesions (>70% of patients have lesions, Morris and Black, 1985), fever, chills and nausea (Bachman et al., 1983; Tacket et al., 1984). Hypotension, abdominal pain, vomiting and diarrhea are less frequently reported. The mortality rate in various studies ranges from 46% (Blake et al., 1980) to 61% (Tacket et al., 1984).

Most patients with sepsis are either immunocompromised (75%, Oliver, 1981; Bachman et al., 1983; Blake et al., 1980; Morris and Black, 1985), and/or male (72%, Tacket et al., 1985; to 90%, Oliver, 1981). The following immunocompromising conditions make individuals more susceptible to sepsis:

It has been suggested that the increased susceptibility among persons with liver disease could be caused by an increase in iron stores, commonly found in patients with alcohol-related liver disease (Tacket et al., 1984; Morris and Black, 1985). Furthermore, women may have lower iron stores than men, which may explain why men are more commonly affected than women (Tacket et al., 1984). This hypothesis was supported in laboratory experiments in which the median lethal dose of V. vulnificus decreased from 1 million cells to slightly >1 cell in iron loaded mice (Wright et al., 1981, as cited in Morris and Black, 1985).

V. vulnificus may also cause septicemia in individuals who have not consumed shellfish. In one case, a man who nearly drowned in the Gulf of Mexico developed pneumonia and died from a lactose + Vibrio, indicating that septicemia may develop via the lungs (Kelly and Avery, 1980). A second case involved a 3 day old infant who acquired gastroenteritis and tested positive for V. vulnificus (Bachman et al., 1983). It is possible that the illness was transmitted to the infant by the mother, who had a mild flu-like illness 72 hours before delivery but no definite infection was identified.

Individuals who expose cuts, sores, burns and abrasions to contaminated seawater are at risk of developing wound infections. Symptoms usually within 12 hours of contact with the water (Blake et al., 1980; Oliver 1981). Wound infections commonly cause fever, chills, inflammation and occasionally, gastroenteritis (Tacket et al., 1984). The mortality rate for individuals with wound infections is approximately 7% (Blake et al., 1980).


There were 32 Vibrio vulnificus isolates received by the CDC between 1981 and 1982; 18 were primary sepsis, 9 were wound infections, and 3 were cellulitis with no apparent wounds (Tacket et al., 1984).

In the U.S., most cases occur when water temperature is warm, from May to October (Blake et al., 1980; Blake, 1983; Bachman et al., 1983; Tacket et al., 1984).

Detection & Protection

Vibrio vulnificus is a naturally occurring bacterium which is not found in association with sewage, and therefore is not detected by the presence of traditional indicator bacteria. Infection can be prevented by thorough cooking of shellfish. Individuals in the "high risk" should be especially careful to cook shellfish properly and should avoid exposing open wounds to seawater.

F. Vibrio Mimicus


Vibrio mimicus was originally misidentified as V. cholerae. The bacteria differs from V. cholerae in its inability to ferment sucrose. V. mimicus is gram-negative, oxidase positive, nonhalophilic and motile by a single flagellum (Shandera et al., 1983). It is most likely a part of the normal marine flora of the Atlantic and Gulf Coasts. Unlike the other Vibrios, V. mimicus (and V. cholerae) do not require salt for growth (Blake 1983).

Vibrio mimicus can cause both gastroenteritis and ear infections. Gastrointestinal illness is associated with consumption of raw oysters and boiled crawfish (Shandera et al., 1983). Ear infections are associated with seawater exposure. The median time of gastroenteritis onset is 24 hours (Shandera et al., 1983). Diarrhea, nausea, vomiting and abdominal cramps are the most commonly reported symptoms (Morris and Black, 1985). Some infected individuals have also experienced fever, headache and bloody diarrhea. Diarrhea lasts a median of 6 days. Between 1977 and 1981 there were 21 cases (19 gastroenteritis and 2 ear infections) reported to the CDC.

Selected Bibliography

Blake, P.A. 1983. Vibrios on the half shell: what the walrus and the carpenter didn't know. Annals of Internal Medicine. 99(4):558-559.

Morris, J.G. & R.E. Black. 1985. Cholera and other Vibrios in the United States. New England Journal of Medicine. 312(6):343-350.

Shandera, W.X., J.M. Jeffrey, M. Johnston, B.R. Davis & P.A. Blake. 1983. Disease from infection with Vibrio mimicus, a newly recognized Vibrio species. Annals of Internal Medicine. 99(2):169-171.

Vibrio hollisae

Vibrio hollisae previously belonged to enteric group EF-13. It is a naturally occurring, halophilic bacteria. No environmental isolates of V. hollisae have been found, although illness is associated with consumption of raw oysters, clams and shrimp (Morris et al., 1982). Between 1971 and 1981, 15 cases of illness were reported to the CDC (Morris et al, 1982). The most common symptoms of V. hollisae infection are diarrhea, vomiting, fever and abdominal pain (Blake, 1983; Morris and Black, 1985). Symptoms usually begin within 5 days of ingestion and persist for one day (range: 4 - 13 days).
IV. Toxins

Ciguatera is the most commonly reported disease associated with consumption of seafood (Morris, 1980). Between 1977 and 1981, 37% of the seafood-borne illness reported to the CDC were attributed to ciguatera (USFDA, 1984). Approximately 80% of the cases are due to weekend fishermen who are unfamiliar with the types of fish commonly ciguatoxic.
By ingesting toxic dinoflagellates, certain species of tropical and subtropical fish can become toxic to humans. The dinoflagellate species most often associated with ciguateric fish is Gambierdiscus toxicus (Yasumoto et al., 1977; Adachi and Fukuyo, 1979 as cited in Taylor, 1979). Other algal species which cause ciguatera include Prorocentrum mexicanum, P. concavum, P. lima, and Ostreopsis lenticularis (Carlson and Tindall, 1985).

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