Cholera (also known as Asiatic cholera or epidemic cholera) is an acute enterotoxin-mediated GI infection caused by the gram-negative bacillus Vibrio cholerae. It produces profuse diarrhea, vomiting, massive fluid and electrolyte loss and, possibly, hypovolemic shock, metabolic acidosis, and death. A similar bacterium, Vibrio parahaemolyticus, causes food poisoning. (See Vibrio parahaemolyticus food poisoning.)
Even with prompt diagnosis and treatment, cholera is fatal in up to 2% of children; in adults, it's fatal in less than 1%. However, untreated cholera may be fatal in as many as 50% of patients. Cholera infection confers only transient immunity.
Humans are the only hosts and victims of V. cholerae, a motile, aerobic organism. It's transmitted through food and water contaminated with fecal material from carriers or people with active infections. Cholera is most common in Africa, southern and Southeast Asia, and the Middle East, although outbreaks have occurred in Japan, Australia, and Europe. Infection also occurs after eating shellfish from recognized environmental reservoirs of cholera, including one that's along the United States’ Gulf of Mexico coast.
Cholera occurs during the warmer months and is most prevalent among lower socioeconomic groups. In India, it's common among children ages 1 to 5, but in other endemic areas, it's equally distributed among all age-groups. Susceptibility to cholera may be increased by a deficiency or an absence of hydrochloric acid.
After an incubation period ranging from several hours to 5 days, cholera produces acute, painless, profuse, watery diarrhea and effortless vomiting (without preceding nausea). As diarrhea worsens, the stools contain white flecks of mucus (rice-water stools). Because of massive fluid and electrolyte losses from diarrhea and vomiting (fluid loss in adults may reach 1 L/hour), cholera causes intense thirst, weakness, loss of skin turgor, wrinkled skin, sunken eyes, pinched facial expression, muscle cramps (especially in the extremities), cyanosis, oliguria, tachycardia, tachypnea, thready or absent peripheral pulses, falling blood pressure, fever, and inaudible, hypoactive bowel sounds.
Patients usually remain oriented but apathetic, although small children may become stuporous or develop seizures. If complications don't occur, the symptoms subside and the patient recovers within a week. However, if treatment is delayed or inadequate, cholera may lead to metabolic acidosis, uremia and, possibly, coma and death. About 3% of patients who recover continue to carry V. cholerae in the gallbladder; however, most patients are free from the infection after about 2 weeks.
In endemic areas or during epidemics, characteristic clinical features strongly suggest cholera.
CONFIRMING DIAGNOSIS A culture of V. cholerae from feces or vomitus indicates cholera; however, definitive diagnosis requires agglutination and other clear reactions to group- and type-specific antisera.
A dark-field microscopic examination of fresh feces showing rapidly moving bacilli (like shooting stars) allows for a quick, tentative diagnosis. Immunofluorescence also allows rapid diagnosis. Diagnosis must rule out Escherichia coli infection, salmonellosis, and shigellosis.
Improved sanitation and the administration of cholera vaccine to travelers in endemic areas can control this disease. Unfortunately, the vaccine now available confers only 60% to 80% immunity and is effective for only 3 to 6 months. Consequently, vaccination is impractical for residents of endemic areas.
Treatment requires rapid I.V. infusion of large amounts (50 to 100 ml/minute) of isotonic saline solution, alternating with isotonic sodium bicarbonate or sodium lactate. Potassium replacement may be added to the I.V. solution. Antibiotic therapy using such drugs as tetracycline, bac-trim, erythromycin, and ciprofloxacin can shorten the course of infection and reduce the rehydration requirement.
When I.V. infusions have corrected hypovolemia, fluid infusion decreases to quantities sufficient to maintain normal pulse and skin turgor or to replace fluid loss through diarrhea. An oral glucose-electrolyte solution can substitute for I.V. infusions. In mild cholera, oral fluid replacement is adequate. If symptoms persist despite fluid and electrolyte replacement, treatment includes tetracycline.
A cholera patient requires contact precautions, supportive care, and close observation during the acute phase.
❑Wear a gown and gloves when handling feces-contaminated articles or when a danger of contaminating clothing exists, and wash your hands after leaving the patient's room.
❑Monitor output (including stool volume) and I.V. infusion accurately. To detect overhydration, carefully observe neck veins, take serial patient weights, and auscultate the lungs (fluid loss in cholera is massive, and improper replacement may cause potentially fatal renal insufficiency).
❑Protect the patient's family by administering oral tetracycline or doxycycline, if ordered.
❑Advise anyone traveling to an endemic area to boil all drinking water and avoid uncooked vegetables and unpeeled fruits.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X 
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