Cholera in Louisiana -- Update

Since mid-August 1986, 12 cases of cholera have been identified among residents of Louisiana. The cases occurred in nine families living in New Orleans and in other towns in six parishes (Jefferson, LaFourche, Assumption, St. Mary, Iberia, and Jefferson Davis) within a 200-mile radius to the south and west of New Orleans. None of the patients had traveled abroad within the past year.

Onset of symptoms occurred between August 8 and October 1. Ten of the patients had severe diarrhea, seven required hospitalization, and four required treatment in an intensive care unit for hypotension. All patients recovered following intravenous fluid therapy. Seven patients had stool cultures yielding toxigenic Vibrio cholerae O1, biotype El Tor, serotype Inaba. The remaining five patients did not have stool cultures performed but had vibriocidal antibody titers greater than or equal to 1280, suggesting recent infection with V. cholerae O1.

Sewer system surveillance using Moore swabs has detected toxigenic V. cholerae O1 in sewage in eight separate sites in southern Louisiana (three in Jefferson Parish, one in Orleans Parish, one in St. Tammany Parish, one in Iberia Parish, and two in Jefferson Davis Parish). Five of these sites are in towns without a clinically identified case of cholera.

Although no common source has been identified, eleven of the patients reported eating crabs or shrimp within 5 days before the onset of symptoms. The seafoods were harvested from multiple sites in a wide area along the Louisiana coast of the Gulf of Mexico. Surveillance is continuing, and further epidemiologic studies are underway. Reported by L McFarland, DrPH, HB Bradford, PhD, J Mathison, MD, State Epidemiologist, Louisiana Dept of Health and Human Resources; Enteric Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases, Div of Field Svcs, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Thirteen cases of domestically acquired cholera (one involving a Florida patient (1)) have been detected near the U.S. Gulf coast so far during 1986. Past studies of El Tor V. cholerae infections in both endemic and non-endemic countries indicate that many mild or clinically inapparent infections occur for every hospitalized patient (2). The detection of toxigenic V. cholerae O1 in the sewer systems of several towns with no identified cases suggests that undetected cases have occurred in Louisiana.

The source of infection, as in 1978 in Louisiana (3), appears to be crustacea. Because seafood from the Gulf Coast is shipped to many states, even physicians located far from the Gulf should consider the possibility of cholera when a patient has severe, watery diarrhea. Diagnosis is confirmed by the isolation of V. cholerae O1 from stool culture, preferably on thiosulfate-citrate-bile salts-sucrose (TCBS) agar. Isolates of V. cholerae should be serotyped and tested for toxin production through state public health laboratories, and all cases should be reported immediately to the state epidemiologist.

In this outbreak, inadequate cooking or improper handling of crustacea appeared to play a significant role in the development of V. cholerae O1 infection. Thoroughly cooking potentially contaminated food and then carefully handling and storing cooked food will prevent foodborne cholera. (V. cholerae O1 has been shown to survive in crabs boiled for 8 minutes, but not in crabs boiled for 10 minutes (3)).

Vigorous rehydration (preferably with Ringer's lactate) and careful correction of electrolyte and acid-base disturbances are the mainstays of therapy and result in very low mortality rates among hospitalized patients. Tetracycline shortens the duration of symptoms and the period of fecal shedding of the organism (4).

References

1. CDC. Toxigenic Vibrio cholerae O1 infections--Louisiana and Florida. MMWR 1986;35:606-7.

2. Harris JR, Holmberg SD, Parker RDR, et al. Impact of epidemic cholera in a previously uninfected island population: evaluation of a new seroepidemiologic method. Am J Epidemiol 1986;123:424-30.

3. Blake PA, Allegra DT, Snyder JD, et al. Cholera--a possible endemic focus in the United States. N Engl J Med 1980;302:305-9.

4. Greenbough WB. In: Mandell GL, Douglas RG Jr, Bennett JE, eds. Principles and practice of infectious diseases. 2nd ed. New York: John Wiley and Sons, 1985:1208-18.

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