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Current Trends Update: Cholera -- Western Hemisphere, and Recommendations for Treatment of Cholera
Epidemic cholera appeared in Peru in January 1991 and subsequently spread to Ecuador, Colombia, Chile, Brazil, Mexico, and Guatemala (Table 1) (1-3). Cholera can be a severe, life-threatening illness but is highly preventable and easily treated; however, few health-care practitioners in the United States have experience identifying and treating cholera. This report provides an update on cholera in the Western Hemisphere and provides recommendations on the clinical diagnosis and treatment of cholera in the United States.
As of August 12, 15 epidemic-associated Vibrio cholerae infections have occurred in the United States (4,5); no secondary spread from these cases has occurred. Since 1973, 65 cholera cases unrelated to the Latin American epidemic have occurred in the United States that were caused by the Gulf Coast strain of toxigenic V. cholerae serotype O1; most cases were related to the consumption of raw and undercooked shellfish from the Gulf of Mexico (6). In addition, approximately two cases of cholera are reported each year among travelers returning to the United States from non-Western Hemisphere countries.
In July, toxigenic V. cholerae O1 resembling the Latin American strain was isolated by Food and Drug Administration (FDA) researchers from oysters taken from closed oyster beds in Mobile Bay, Alabama, off the Gulf of Mexico. No human illness has been associated with these oysters, and further sampling of commercial seafoods from the Gulf by the FDA has not identified other foci of contamination.
Reported by: Enteric Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.
Proper treatment of sewage and drinking water in the United States should prevent transmission of cholera by these routes within the United States. Because of the considerable travel between Latin America and the United States, and because of the presence of the Gulf Coast strain, additional cases of cholera may occur. With clinical awareness of signs and symptoms of cholera, and knowledge of appropriate treatment, cholera should not pose a major risk to health in the United States.
Microbiology. Cholera is caused by V. cholerae serogroup O1 strains that produce cholera toxin. The Latin American epidemic strain is biotype El Tor, serotype Inaba. This strain can be distinguished from the strain of V. cholerae O1 that is endemic to the U.S. Gulf Coast by hemolysin production and by molecular subtyping techniques (7).
Clinical Suspicion. Cholera should be suspected in a patient with severe watery diarrhea, vomiting, and dehydration. The illness is often accompanied by marked leg cramps, caused by electrolyte disturbances. However, the spectrum of V. cholerae O1 infection ranges from asymptomatic infection (75% of infections) through mild diarrhea to the most severe and clinically recognizable form (5%). Clinical suspicion should be increased for persons returning from areas known to have epidemic cholera or for persons with a recent history of ingestion of raw or undercooked shellfish.
Diagnosis. Cholera is diagnosed by isolation of toxigenic V. cholerae serotype O1 from feces. Other serogroups of V. cholerae, and nontoxigenic V. cholerae O1, may be isolated from stools of patients with diarrhea, but these bacteria are not associated with epidemic cholera. Culture of rectal swabs or fecal specimens on thiosulfate citrate bile salts sucrose (TCBS) medium should be requested for any patient suspected to have cholera. Suspected isolates of V. cholerae should be submitted to public health laboratories for confirmation. Serologic diagnosis may also be made by the presence of a changing titer of vibriocidal antibodies.
Treatment. Patients suspected of having cholera should be treated aggressively while awaiting culture results. In both adults and children, fluid and electrolyte losses should be replaced by rehydration therapy. All but severely dehydrated adults and children can be managed largely or completely with oral rehydration solution (ORS) (8). Patients with mild to moderate vomiting will absorb ORS taken in small sips. At present, World Health Organization ORS packets (WHO-ORS,* Jianas Brothers, St. Louis), RicelyteTM (Mead Johnson), and RehydralyteR (Ross Laboratories) are the only oral solutions available in the United States that contain the proper balance of electrolytes for treating cholera. WHO-ORS is available from the manufacturer; the other two products are available over the counter. If ORS is not available, rehydration therapy should begin with intravenous fluids.
Intravenous therapy is necessary for patients who are severely dehydrated or in hypovolemic shock. The severely dehydrated cholera patient may have lost more than 10% of body weight and will need rapid volume replacement with Ringer's Lactate solution, the only solution readily available in the United States with the electrolyte composition needed for treating cholera (9,10). Normal saline is less effective for treatment but can be used if Ringer's Lactate is unavailable (10). Severely dehydrated adults may require several liters of fluid immediately to restore an adequate circulating volume. As soon as the patient is hemodynamically stable, oral therapy may be substituted. Patients with cholera have substantial on-going fluid losses that also need to be replaced.
Antimicrobial drugs are a useful adjunctive therapy, decreasing the duration of both diarrhea and bacterial shedding and diminishing the volume of fluid replacement needed for treatment. Antibiotics with demonstrated effectiveness include doxycycline, tetracycline, trimethoprim-sulfamethoxazole (TMP-SMX), erythromycin, and furazolidone (9,10). Adults may be treated with a single 300-mg dose of doxycycline. Children may be given TMP-SMX twice a day for 3 days at a dose of 5 mg/kg of TMP and 25 mg/kg of SMX.
Management of Family Contacts. Family members of persons suspected to have cholera should be questioned concerning their health status and advised to seek medical attention immediately if they develop watery diarrhea during the week following illness onset in the index patient. Because secondary transmission in the United States is rare, chemoprophylaxis of family contacts is not necessary. Cholera vaccine is not recommended (4). The family should receive instructions about proper hand washing and about cleaning contaminated clothes and linen with soap and chlorine bleach. The sanitary facilities in a cholera patient's home should be inspected to ensure that the patient's feces are disposed of through adequate sewage treatment or a functioning septic tank or are otherwise decontaminated.
Case Reporting. All suspected or confirmed cases of cholera should be reported immediately to the local and state health department.
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