Define Cholera. Describe its pathogenesis, clinical features, management and prevention.

Definition

Cholera is an acute secretory diarrhoeal illness caused by the toxin of Vibrio cholerae (serogroups O1 and O139), capable of causing severe, rapidly dehydrating watery diarrhoea and epidemics.

Pathogenesis

• The organism is transmitted faeco-orally through contaminated water/food.
• Cholera toxin activates adenylate cyclase → ↑ cAMP → massive active secretion of chloride and water into the gut lumen → profuse watery diarrhoea. The mucosa itself is not invaded.

Clinical Features

• Sudden onset of painless, profuse 'rice-water' stools (watery with flecks of mucus) and vomiting.
• Rapid, severe dehydration → sunken eyes, washerwoman's hands, hypovolaemic shock; muscle cramps (electrolyte loss).
• Little or no fever; the child can lose fluid faster than in any other diarrhoea.

Management

• Aggressive rehydration is life-saving — IV Ringer lactate for severe cases (Plan C), then ORS; rice-based ORS reduces stool volume.
• Replace ongoing large stool losses volume-for-volume; monitor and correct potassium.
• Antibiotics (as an adjunct) shorten the illness and reduce stool volume — doxycycline (single dose) or azithromycin as per sensitivity.
• Zinc for 14 days; continue feeding.

Prevention

• Safe water & sanitation, hand-washing, food hygiene; case isolation and surveillance in outbreaks.
• Oral cholera vaccines in high-risk/epidemic settings.

Epidemiology

• Occurs in epidemics linked to contaminated water and poor sanitation, often after floods or in crowded settings.
• Humans are the only reservoir; the disease is notifiable.

Investigations

• Clinical diagnosis in an outbreak; stool hanging-drop microscopy shows darting motile vibrios.
• Stool culture on TCBS medium confirms the organism; assess electrolytes in severe cases.

Complications

• Hypovolaemic shock, acute kidney injury, severe hypokalaemia and metabolic acidosis; hypoglycaemia in children.