Cholera

Cholera is also called Asiatic cholera and epidemic cholera. It's an acute, enterotoxin-mediated GI infection caused by the gram-negative rod Vibrio cholerae. Cholera produces profuse diarrhea, vomiting, and fluid and electrolyte losses. A similar bacterium, Vibrio parahaemolyticus, causes food poisoning.

Cholera is native to the Ganges delta in the Indian subcontinent. Pandemics have affected the United States Gulf Coast of Louisiana and Texas and Latin and Central America. Southeast Asia has also had outbreaks. It usually occurs during the warmer months and is most prevalent in coastal areas among lower socioeconomic groups. In India, cholera is especially common among children ages 1 to 5, but in other endemic areas, it's equally distributed among all age groups.

Even with prompt diagnosis and treatment, cholera can be rapidly fatal because of difficulty with fluid replacement. Cholera infection confers only transient immunity. About 3% of patients who recover continue to carry V. cholerae in the gall bladder; however, most patients are free from the infection after about 2 weeks.

Causes

Cholera is caused by a germ known as vibrio cholerae. This germ produces a powerful poison or endotoxin. The disease is spread by flies and water contaminated by the germs.

Symptoms and Signs

Symptoms include:

• Watery diarrhea
• Vomiting
• Leg cramps
• Loose stools
• Nausea
• Thirsty feeling
• Restlessness
• Rise in temperature
• Fall in blood pressure

The infection is often mild or without symptoms.

Diagnostic tests

A culture of V. cholerae from stool or vomitus indicates cholera, but definitive diagnosis requires agglutination and other clear reactions to group and type-specific antisera.

A dark-field microscopic examination of fresh stool 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, salmonella infection, and shigellosis.

Treatment

Travelers to endemic areas can receive the cholera vaccine. Vaccination is impractical for residents of endemic areas due to cost at this time. Only an improvement in sanitation can control the disease.

When the patient has cholera, he requires rehydration by oral fluids containing sodium at 90 mmol/L to replace losses in the stool. For severe dehydration, often accompanied by acidosis, I.V. fluid is preferred, particularly Ringer's lactate, to replace losses. Total fluid deficit in severely dehydrated patients can be replaced in the first 4 hours of therapy; half within the first hour. Oral rehydration of electrolytes, particularly potassium, is safer than by the I.V. route. Thirst and urine output guide fluid replacement. The patient also may receive calcium and magnesium replacements in the I.V. solution.

After the I.V. infusions have corrected hypovolemia, the patient only needs fluid infusions sufficient to maintain normal pulse rate and skin turgor or to replace fluid lost through diarrhea. An oral glucose-electrolyte solution can be substituted for I. V. infusions.

In mild cholera, the patient only needs early oral fluid replacement. A patient who is suspected of having cholera can receive a single dose of doxycycline or tetracycline. However, with the emergence of bacterial strains that resist traditional antibiotic therapy, he's likely to receive ciprofloxacin or erythromycin instead. Antibiotic therapy shortens the duration of diarrhea, diminishing fluid and electrolyte losses.

Alert

Tetracycline-type antibiotics aren't recommended for children under age 8 because of possible deposition in the bones and developing teeth, resulting in permanent changes.

Prevention

A vaccine for cholera is available; however, it confers only brief and incomplete immunity and is not recommended for travelers. There are no cholera vaccination requirements for entry or exit in any Latin American country or the United States.

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