Cholera

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Cholera is an acute infective diarrheal illness caused by Vibrio cholerae. Severe cholera causes large volume liquid stools, which may rapidly lead to hypovolemic shock and death, unless intensive rehydration therapy is instituted. Prevention of cholera depends upon access to clean water and effective sanitation, and effective vaccines are now available.

Epidemiology

Cholera is endemic in more than 50 territories with multiple pandemics since 1817. The seventh pandemic commenced in 1961, with up to 5 million new cases per annum, with ~120,000 deaths . Diarrheal conditions are the second commonest cause of death globally in under five-year-olds, and a major cause of morbidity .

The incubation period of cholera lasts anything from 12 hours to 5 days.

Clinical presentation

The primary presenting feature is diarrhea, classically of a "rice water" character with a fishy odor and painless in nature. The diarrhea may be anything from mild to severe in both volume and/or frequency of the liquid stool. In severe cases the volume may exceed one liter per hour, which rapidly leads to shock and death.

Other symptoms:

Fever is distinctly unusual, and if present should prompt a search for an alternative diagnosis or a concurrent infection.

Rarely, the disease may present as the “cholera sicca” form, in which large volumes of fluid collect in the bowel lumen, and hypovolemic shock, even death, may occur before any diarrhea is seen.

Complications

Most of the complications result from the associated dehydration, which may be severe:

  • lassitude
  • tachycardia
  • diminished skin turgor
  • decreased urine output
  • hypotension
  • tachypnea

Loss of large volumes of stool may also lead to marked electrolyte imbalances:

  • hypokalemia: tiredness, muscle weakness, ileus and arrhythmias
  • hypernatremia
  • hypoglycemia: due to depletion of glycogen stores and inadequate hepatic gluconeogenesis
Diagnosis
  • isolation of V. cholerae on stool or rectal swab culture is the gold standard diagnostic test

Pathology

Etiology

The infective agent is Vibrio cholerae, a member of the Vibrionaceae family of curved, Gram-negative rods, commonly normally present in coastal waters (like other Vibrio spp.).

V. cholerae is subdivided into greater than 200 serogroups, related to the O antigen of a lipopolysaccharide. Only the O1 and O139 serogroups produce epidemic cholera. O1 is typed into classical and El Tor biotypes. El Tor is responsible for the current pandemic, classical was responsible for all preceding epidemics.

Multidrug resistant strains of O1 and O139 have become an increasing problem in Asia.

Treatment and prognosis

Aggressive intravenous fluid resuscitation for moderate to severe disease. Oral rehydration therapy for the mild cases.

Antibiotics decrease duration of the diarrhea and reduce the chance of transmission to uninfected individuals . Unfortunately like many infections antibiotic resistance is an increasing problem, many strains are now resistant to macrolides (e.g. azithromycin), which used to be the mainstay of successful antimicrobial therapy .

Death may result in as little as six to twelve hours after onset of the diarrhea if severe, and fluid resuscitation is not provided/delayed.

Complications

Severe, untreated disease may rapidly lead to

  • hypovolemic shock
  • end-organ damage
  • seizures: disturbed biochemistry
  • death: in as little as 6-12 hours in fulminant disease (cholera gravis)