Cholera

• Cholera is a dreaded diarrheal illness known for its severity and potential to cause outbreaks.
• The disease continues to be a burden in resource-poor countries lacking access to safe water supply and sanitation.
• The term "cholera" likely originates from the Greek word for the 'gutter of a roof,' likening the deluge of water after a rainstorm to the flow from the anus of an infected person.
• Cholera is an ancient disease caused by Vibrio cholerae.
• Endemic: Common in resource-poor areas.
• Epidemic: Occurs during natural disasters and emergencies, affecting displaced people, slums, and institutionalized populations.
• Pandemic disease: Affects a wide geographic area.
• Despite significant advances in research, cholera remains a challenge for developing countries.

• Cholera is rare in developed countries.
• Statistics on cholera worldwide are uncertain.

Contributory Factors

• Most cases occur in remote areas where definitive diagnosis is not possible.
• Reporting systems are often non-existent in such areas.
• The stigma of reporting cholera has direct consequences on commercial trade and tourism.
• Many countries with endemic cholera do not report at all.

• Vibrio cholerae is a saltwater organism and its primary habitat is the marine ecosystem.
• There are about 140 known serogroups of V. cholerae, only serogroups 01 and 0139 cause epidemics.
• Other serotypes cause non-cholera gastroenteritis with occasional extra-intestinal manifestations.
• Cholera has 2 main reservoirs: humans and water. V. cholerae is rarely isolated from animals, and animals do not play a role in disease transmission.
• Vibrio cholerae belongs to the family Vibronaceae.
• It is a non-spore forming organism, slightly curved, gram-negative, aerobic bacillus, with flagellum.
• It has antigenic structures:
  • Flagella H antigen
  • Somatic O antigen
• It produces a potent enterotoxin known as CTX.

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• Cholera toxin (CTX) is a potent protein enterotoxin elaborated by the organism in the small intestine.
• The organism has to negotiate the normal defense mechanisms of the gastrointestinal (GI) tract.
• A large inoculum of bacteria (≥∼10⁸ viable units) is required.
• The organisms produce CTX that consists of subunits A and B.
• The B subunits bind to the GM1 ganglioside receptors in the small intestinal mucosa, allowing the A subunit to enter into the cell.
• Activation of adenylate cyclase, leading to an increase in cyclic adenosine monophosphate (AMP).
• Cyclic AMP blocks the absorption of sodium chloride by the microvilli and promotes the secretion of chloride and water by the crypt cells.
• The result is massive outpouring of electrolyte-rich isotonic fluid into the small intestine (about 10-12L).
• The large volume of fluid produced in the upper intestine overwhelms the absorptive capacity of the lower bowel (daily absorption by the large intestine is between 5-8L), resulting in severe diarrhea.
• The diarrheal fluid contains large amounts of sodium, chloride, bicarbonate, and potassium.
• Since the enterotoxin acts locally and does not invade the intestinal wall, few red blood cells and neutrophils are found in the stool.
• The loss of electrolyte-rich isotonic fluid leads to blood volume depletion with resulting low blood pressure and shock.
• Loss of bicarbonate and potassium leads to metabolic acidosis and hypokalemia.

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• Primary infection in humans is acquired incidentally.
• Risk of primary infection is facilitated by seasonal increases in the number of organisms from changes in water temperature and algal blooms.
• Secondary transmission occurs through fecal-oral spread of the organism through person-to-person contact or through contaminated water and food.

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• Poor sanitary conditions
• Household exposures
• Age
• Non-breastfed infants
• Hydrochlorhydria or Achlorhydria
• Malnutrition
• Raw or undercooked shellfish and vegetables
• O blood group
• Previous exposure and acquired immunity
• Asymptomatic carriers

• Diarrhea:
  • Profuse watery diarrhea is a hallmark of cholera.
  • V cholerae does not elicit an inflammatory response, and cholera stool contains few leukocytes and no erythrocytes.
  • High stool volume >250 mL/kg body weight in a 24-hour period.
  • The characteristic cholera stool is an opaque white liquid that is not malodorous and often is described as having a rice water appearance.
• Frequent and often uncontrolled bowel movements.
• Abdominal cramps
• Vomiting
• Decreased gastric and intestinal motility
• Acidaemia
• Isotonic dehydration which could lead to vascular collapse, shock, and death.
• Dehydration can develop with remarkable rapidity, within hours after the onset of symptoms.
• Water loss is proportional between 3 body compartments: intracellular, intravascular, and interstitial.
• Signs of Dehydration
• Tachypnea and hypercapnia attributable to the metabolic acidosis.
• Metabolic and systemic manifestations:
  • Hypoglycemia is the most common lethal complication of cholera in children.
  • Metabolic acidosis:
    • Tachypnea and tachycardia.
  • Hypokalemia.
  • Hyponatremia.
  • Hypocalcemia.
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• Direct microscopic examination:
  • Gram stain.
  • Dark field organism.
• Culture:
  • Routine differential media.
  • Alkaline enrichment media.
• Serotyping and biotyping.
• Hematological tests:
  • Hematocrit, serum-specific gravity, and serum protein are elevated.
  • Leucocytosis without a left shift.
• Serum electrolytes.
• Renal profile:
  • Blood urea nitrogen and serum creatinine are elevated.

Causes of Gastroenteritis

• Rotavirus: A highly contagious virus that primarily affects infants and young children, causing severe diarrhea, vomiting, and fever.
• Escherichia coli (E. coli): Various strains of E. coli, such as enterotoxigenic E. coli (ETEC) and enteropathogenic E. coli (EPEC), are responsible for traveler's diarrhea and endemic cases of gastroenteritis.
• Salmonella: Different species of Salmonella bacteria can lead to foodborne illnesses and gastroenteritis with symptoms like diarrhea, abdominal cramps, and fever.
• Shigella: Shigella species cause bacillary dysentery, characterized by bloody diarrhea, abdominal pain, and fever.
• Entamoeba histolytica: This parasite causes amoebic dysentery, leading to bloody diarrhea and potential systemic complications.
• Giardia lamblia: A protozoan parasite that causes giardiasis, often resulting in diarrhea, abdominal pain, and other gastrointestinal symptoms.
• Norovirus: A highly contagious virus that causes outbreaks of gastroenteritis, with symptoms like nausea, vomiting, diarrhea, and stomach cramps.
• Cryptosporidium: A parasite responsible for cryptosporidiosis, leading to watery diarrhea and other gastrointestinal symptoms.
• Helminthic Infections: Parasitic worms like Ascaris lumbricoides, Trichuris trichiura, and hookworms can cause chronic gastrointestinal issues in tropical areas.
• Typhoid Fever: Caused by Salmonella typhi bacteria, typhoid fever leads to high fever, abdominal pain, and gastrointestinal complications.

• The disease:
  • Dehydration
  • Hypovolemic shock
  • Renal failure
  • Electrolyte imbalances
  • Hypoglycemia
• Therapy:
  • Over-hydration
  • Pulmonary edema

1. Assess for dehydration
2. Rehydrate the patient and monitor frequently. Maintain hydration
3. Administer an antibiotic to patients with severe dehydration*.
4. Feed the patient.

*Doxycycline, tetracycline, ampicillin, ciprofloxacin, erythromycin, trimethoprim and sulfamethoxazole*

• Maintain high level of hygiene
• Scrupulous hand wash
• Proper disposal of faeces
• Proper handling of faeces
• Use of disposable gloves
• Ensure frequent disinfection of designated room(s)