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Back to Infectious Diseases
Cholera
Cholera is an
acute diarrheal disease that can, in a matter of hours,
result in profound, rapidly progressive dehydration and death. It is caused
by infection with the bacterial organism known as V. cholerae.
Humans become infected incidentally but, once infected, can act as
vehicles for spread. Ingestion of water contaminated by human feces is
the most common means of acquisition of V. cholerae. Consumption of contaminated
food in the home, in restaurants, or from street vendors can also contribute
to spread.
Cholera is a toxin-mediated disease. Its characteristic watery
diarrhea
is due to the action of cholera toxin (CTX), a potent protein enterotoxin
elaborated by the organism following its colonization of the small intestine.
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Clinical manifestations
It passes through 3 phases: Evacuation (profound watery
diarrhea),
collapse (hypovolemic shock) and recovery phases.
After a 24- to 48-h incubation period, cholera begins with the sudden
onset of painless watery
diarrhea that may quickly become voluminous and
is often followed shortly by vomiting. In severe cases, stool volume can
exceed 250 mL/kg in the first 24 h. If fluids and electrolytes are not
replaced, hypovolemic shock and death ensue. Fever is usually absent.
Muscle cramps due to electrolyte disturbances are common. The stool has
a characteristic "rice-water" appearance because of its resemblance to
the water in which rice has been washed.
Diagnosis
The clinical suspicion of cholera can be confirmed by the identification
of V. cholerae in stool; however, the organism must be specifically sought.
In experienced hands, it can be detected directly by dark-field microscopy
on a wet mount of fresh stool, and its serotype can be discerned by immobilization
with Inaba- or Ogawa-specific antiserum.
Treatment
Cholera is simple to treat; only the rapid and adequate replacement
of fluids, electrolytes, and base is required. Oral rehydration solution
(ORS) with the WHO formulation forms the standard of therapy.
For initial management of severely dehydrated patients, intravenous
fluid replacement is preferable, if available. Because profound acidosis
(pH < 7.2) is common in this group, Ringer's lactate is the best choice
among commercial products. It must be used with additional potassium supplements,
preferably given by mouth.
Although not necessary for cure, the use of an antibiotic to which
the organism is susceptible will diminish the duration and volume of fluid
loss and will hasten clearance of the organism from the stool. Single-dose
tetracycline (2 g) or doxycycline (300 mg) is effective in adults.
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