Seafood Safety
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:
- Liver disease (cirrhosis and haemchromatosis)
- Alcohol abuse
- Cancer (especially persons treated with anticancer drugs and radiation)
- Diabetes mellitus
- Chronic kidney disease
- Inflammatory bowel disease (especially persons treated with
immunosuppressive drugs)
- Steroid dependency (for treatment of asthma)
- Achlorhydria (condition in which normal stomach acidity is reduced or
absent)
- AIDS
- Pregnancy
- Epilepsy
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).
Statistics
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
Description
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
Description
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
Description
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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