OPHEPR; Cholera - Profile for Healthcare Workers

Causative Agent: Vibrio cholerae is a motile, gram negative, non-sporulating rod. Two serogroups have been identified as causing symptoms in humans: O1 and O139. These organisms grow best at a pH of 7.0 but are able to tolerate an alkaline environment. Rather than invading the intestinal mucosa, they adhere to it. The clinical syndrome is caused by the action of the cholera toxin.

Route of Exposure: Ingestion of water or food contaminated with cholera organisms.

Infective Dose & Infectivity: 10 to 500 organisms

Incubation Period: The incubation period for cholera ranges from four hours to five days with an average of 2-3 days.

Clinical Effects: Sudden onset of vomiting, abdominal distension, headache and pain with little or no fever. These symptoms are followed rapidly by profuse watery diarrhea with a “rice water” appearance (colorless with small flecks of mucous). Fluid loss may exceed five to ten liters a day, and death can result from dehydration, hypovolemia and shock. In children, coma, seizures and hypoglycemia can occur.

Lethality: If appropriately treated the mortality rate is less than 1%. However, if untreated the mortality rate may exceed 50%.

Transmissibility: Cholera is not easily spread from person to person; infected food handlers can contaminate foods and drinks; in order to be an effective biological weapon, major drinking water supplies would need to be heavily contaminated.

Primary Contamination & Methods of Dissemination: Natural dissemination is through fecal contamination of food or water supply.

Secondary Contamination & Persistence of organism: Diarrheal fluids are highly infective, however, the organism is easily killed by desiccation. It is not viable in pure water but will survive up to 24 hours in sewage and as long as six weeks in water containing organic matter. Vibrio cholerae can also withstand freezing for 3 to 4 days.

Decontamination & Isolation:

Patients – Patients with cholera and uncontrolled diarrhea should be managed using contact precautions that means using gloves and gowns for any contact with the patient or his environment. Good hand washing before and after glove use is essential to prevent spread of pathogens. Diapered or incontinent patients should remain on contact isolation for the duration of diarrhea symptoms. No airborne isolation of patients is necessary.
Equipment, clothing & other objects – Vibrio cholerae is readily killed by dry heat at 117^o C, steam, boiling or by short exposure to ordinary disinfectants and chlorination of water. Clothing should be washed in soap and hot water.

Outbreak control: Quarantine is unnecessary. Any person who shared food or drink with a cholera patient should be under surveillance for five days, and objects contaminated with feces or vomitus should be disinfected prior to reuse. Feces and vomitus do not need to be disinfected if discharged into a normal sewage disposal system.

Laboratory Testing: Vibrio cholerae can be cultured from stool specimens.

Therapeutic Treatment: Treatment of cholera infection is through rehydration with oral or parenteral fluids. Antibiotics can be used to shorten the duration of the diarrhea and the shedding of the organism. Oral tetracycline or doxycycline should be used. If patients are infected with a tetracycline-resistant strain, ciprofloxacin or erythromycin can be used. Although tetracyclines are usually avoided in children under eight due to the concern of teeth staining, the short course of therapy is unlikely to cause problems.

Prophylactic Treatment: Although a vaccine exists, it is not recommended because of its partial efficacy. Household contacts with a high likelihood of secondary transmission may receive oral tetracycline or doxycycline prophylaxis. Mass antibiotic prophylaxis of whole communities is never indicated and can lead to antibiotic resistance.

Differential Diagnosis: The differential diagnosis for V. cholerae includes organisms causing secretory diarrhea such as enterotoxigenic E. coli, and Vibrio parahemolyticus.

References:

Chin J. Control of Communicable Diseases Manual, Seventeenth Edition, American Public Health Association; 2000.
Kortepeter M, Christopher G, Cieslak T, et al. Medical Management of Biological Casualties Handbook, U.S. Army Medical Research Institute of Infectious Diseases, U.S. Department of Defense; 2001.
Zajtchuk R, Bellamy RF, eds. Medical Aspects of Chemical and Biological Warfare. Washington, DC: Office of the Surgeon General, U.S. Department of the Army; 1997.

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