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Vibrio vulnificus Infections Associated with Eating Raw Oysters -- Los Angeles, 1996

Of all foodborne infectious diseases, infection with Vibrio vulnificus is one of the most severe; the case-fatality rate for V. vulnificus septicemia exceeds 50% (1,2). In immunocompromised hosts, V. vulnificus infection can cause fever, nausea, myalgia, and abdominal cramps 24-48 hours after eating contaminated food; because the organism can cross the intestinal mucosa rapidly, sepsis and cutaneous bullae can occur within 36 hours of the initial onset of symptoms. Cases are most commonly reported during warm-weather months (April-November), and often are associated with eating raw oysters. During April 1993-May 1996, a total of 16 cases of V. vulnificus infection were reported in Los Angeles County. Fifteen (94%) of these patients were primarily Spanish-speaking, 12 (75%) had preexisting liver disease (associated with alcohol use or viral hepatitis), all were septicemic, and all had eaten raw oysters 1-2 days before onset of symptoms. In May 1996, three deaths related to V. vulnificus infection among primarily Spanish-speaking persons were reported to the Los Angeles County Department of Health Services (LACDHS). This report summarizes the findings of the investigations of these fatal cases and illustrates the importance of prevention strategies for persons with preexisting liver disease. Case Investigations

Case 1. On May 1, 1996, a 38-year-old man had onset of fever, chills, nausea, and myalgia. On April 29, he had eaten at home raw oysters purchased from a retail store. On May 2, he was admitted to a hospital because of a fever of 102 F (39 C) and two circular necrotic lesions on the left leg. He reported a history of regular beer consumption (36-72 oz per day) and insulin-dependent diabetes. Sepsis and possible deep-vein thrombosis were diagnosed, and the patient was transferred to the intensive-care unit (ICU). In the ICU, therapy was initiated with ticarcillin/clavulanic acid, gentamicin, vancomycin, and ceftazidime. On May 3, V. vulnificus was isolated from the blood sample obtained from the patient on admission, and ciprofloxacin was added to his therapy. On May 4, he died. Traceback of the oysters by environmental health inspectors indicated they originated from a lot harvested in Galveston Bay, Texas, on April 27.

Case 2. On May 10, a 46-year-old man had onset of fever, sweats, and nausea. On May 9, he had eaten at home raw oysters purchased from a retail store. On May 11, he was admitted to a hospital because of a fever of 101.5 F (38.5 C), jaundice, and ascites. He reported a history of heavy alcohol use (72 oz of beer per day) and alcoholic liver disease; in 1995, he had had jaundice for 1 month and had cirrhosis diagnosed. In the hospital, sepsis of unknown etiology was diagnosed, and he was transferred to the ICU; therapy was initiated with piperacillin and gentamicin. On May 12, he died. V. vulnificus was isolated from samples of blood and peritoneal fluid obtained on admission. Traceback of the oysters by environmental health inspectors indicated they originated from a lot harvested in Galveston Bay on May 4; however, harvesters associated with case 1 were different from those for case 2.

Case 3. On May 20, a 51-year-old woman had onset of fever, nausea, and muscle aches. On May 19, she had eaten raw oysters served at a party. On May 21, she was admitted to a hospital because of a fever of 105 F (40.5 C) and bilateral leg cellulitis. In 1982, she had had breast cancer diagnosed and in 1986, chronic hepatitis C. Following the cellulitis, hemorrhagic bullous lesions developed, then septic shock, and the patient was transferred to the ICU. Therapy was initiated with ticarcillin/clavulanic acid and one dose each of ciprofloxacin and doxycycline. On May 22, she died. V. vulnificus was isolated from blood and wound cultures obtained on admission. Traceback of the oysters by environmental health inspectors indicated they originated from a lot harvested in Eloi Bay, Louisiana, on May 14. Follow-Up Investigation

During the investigation of cases 1-3, no implicated oysters were available for analysis. Because V. vulnificus is present in up to 50% of oyster beds with the water conditions that prevail in the Gulf of Mexico during warm months (i.e., temperature greater than 68 F {greater than 20 C} and salinity of less than 16 parts per thousand) (3), no oysters from these waters were obtained for analysis following the tracebacks. Other than ingestion of oysters, no other known source of exposure to V. vulnificus (e.g., ingestion of other raw shellfish or skin exposure to seawater or shellfish) was identified for the three case-patients, and no cases of V. vulnificus-associated illness were identified among the persons who ate raw oysters with the case-patients.

As a result of these three deaths, LACDHS initiated an educational campaign to inform health-care providers and public health professionals about prevention of V. vulnificus infection. Brochures published in English and Spanish also were distributed to immunocompromised persons, including persons with liver disease, to warn them about the hazards of eating raw shellfish.

Reported by: L Mascola, MD, M Tormey, MPH, D Dassey, MD, Acute Communicable Disease Control, L Kilman, S Harvey, PhD, Public Health Laboratory, A Medina, A Tilzer, Consumer Product Div, Food and Milk Inspection Program, Los Angeles County Dept of Health Svcs; S Waterman, MD, State Epidemiologist, California State Dept of Health Svcs. Foodborne and Diarrheal Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; State Br, Div of Applied Public Health Training (proposed), Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: V. vulnificus is a gram-negative bacterium that causes septicemia, wound infections, and gastroenteritis. Transmission occurs through ingestion of contaminated raw or undercooked seafood, especially raw oysters, or through contamination of a wound by seawater or seafood drippings. Persons with liver disease are at particularly high risk for fatal septicemia following ingestion of contaminated seafood; immunocompromised persons also are at increased risk (1,4,5).

The findings in this report suggest that these three fatal cases of V. vulnificus infection were associated with eating contaminated raw oysters. Three factors support this conclusion: 1) V. vulnificus infection previously has been associated only with sea-water, brackish water, or shellfish; 2) ingestion of raw oysters was the only known source of exposure for these three cases; and 3) the implicated oysters were harvested in waters in which V. vulnificus is commonly present during warm months.

Although there is no national surveillance system for V. vulnificus infections, the Gulf Coast states, in collaboration with CDC, conduct regional Vibrio surveillance; Alabama, Florida, Louisiana, and Texas have participated since 1988 and Mississippi, since 1989. From 1988 through 1995, CDC received reports of 302 V. vulnificus infections from the Gulf Coast states; of these, 141 (47%) were associated with eating contaminated seafood, 128 (42%) with wound infections, and 33 (11%) with unknown sources. Of the 141 persons with V. vulnificus infections associated with ingestion, 136 (96%) had eaten raw oysters. Among the 242 persons for whom outcome was known, 86 (36%) died (CDC, unpublished data, 1996).

V. vulnificus thrives in warm sea water (3). The organism is frequently isolated from shellfish from the Gulf of Mexico (3) and from shellfish harvested from U.S. Pacific (6) and Atlantic (7) coastal waters. Although oysters can be harvested legally only from waters devoid of fecal contamination, even legally harvested oysters can be contaminated with V. vulnificus because the bacterium is naturally present in marine environments. V. vulnificus contamination does not alter the appearance, taste, or odor of oysters. Regulations in California and other states requiring oyster lot tagging, labeling, and record retention have facilitated traceback investigations. From 1990 through 1995, the Food and Drug Administration (FDA) and state officials traced oysters eaten by 26 patients who acquired V. vulnificus infections in states outside the Gulf Coast region; among oysters that could be traced to the harvest site (19 cases), all had been harvested in the Gulf of Mexico (FDA, unpublished data, 1996). Timely, voluntary reporting of V. vulnificus infections to CDC and regional FDA shellfish specialists enhances ongoing collaborative efforts to improve investigation and control of these infections. Regional FDA specialists with expert knowledge about shellfish assist state officials with tracebacks of shellfish and, when notified rapidly about cases, are often able to identify and sample harvest waters.

In California, Florida, and Louisiana, warning notices are required to be posted at sites of raw oyster sales. However, these states do not require notices in languages other than English; this policy may decrease the effectiveness of warning notices in areas such as Los Angeles where use of languages other than English is common. For example, the three persons described in this report were fluent in Spanish and spoke English as a second language. Information about consumption of raw oysters is available 24 hours a day in English and Spanish from FDA's Seafood Hotline, telephone (800) 332-4010 or (202) 205-4314.

Because of the high case-fatality rate of V. vulnificus infections in persons with preexisting liver disease or immunocompromising conditions, these persons especially should be informed about the health hazards associated with consumption of raw or undercooked seafood, particularly oysters (2,8,9); the need to avoid contact with sea water during the warm months; and the importance of using protective clothing (e.g., gloves) when handling shellfish (8). Health-care providers should consider V. vulnificus infection in the differential diagnosis of fever of unknown etiology. In addition, providers should ask about a history of raw oyster ingestion or sea water contact when persons with preexisting liver disease or immunocompromising conditions present with fever (especially when bullae, cellulitis, or wound infection is also present) and should promptly administer appropriate antibiotic therapy (tetracycline or a third-generation cephalosporin {e.g., ceftazidime or cefotaxime}) when indicated.


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  2. CDC. Vibrio vulnificus infections associated with raw oyster consumption -- Florida, 1981-1992. MMWR 1993;42:405-7.

  3. Kelly MT. Effect of temperature and salinity on Vibrio (Beneckea) vulnificus occurrence in a Gulf Coast environment. Appl Environ Microbiol 1982;44:820-4.

  4. Johnston JM, Becker SF, McFarland LM. Vibrio vulnificus: man and the sea. JAMA 1985;253: 2850-3.

  5. Blake PA, Merson MH, Weaver RE, Hollis DG, Heublein PC. Disease caused by a marine Vibrio: clinical characteristics and epidemiology. N Engl J Med 1979;300:1-5.

  6. Kelly MT, Stroh EM. Occurrence of Vibrionaceae in natural and cultivated oyster populations in the Pacific Northwest. Diagn Microbiol Infect Dis 1988;9:1-5.

  7. Tilton RC, Ryan RW. Clinical and ecological characteristics of Vibrio vulnificus in the northeastern United States. Diagn Microbiol Infect Dis 1987;6:109-17.

  8. Whitman CM, Griffin PM. Preventing Vibrio vulnificus infection in the high-risk patient. Infectious Diseases Clinical Practice 1993;2:275-6.

  9. Food and Drug Administration. If you eat raw oysters, you need to know. Washington, DC: US Department of Health and Human Services, Public Health Service, 1995; DHHS publication no. (FDA)95-2293.

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