Cholera and Other Vibrioses¶
Chapter 173 | Part 5: Infectious Diseases
KEY CLINICAL POINTS¶
- Cholera is an acute diarrheal disease caused by Vibrio cholerae serogroups O1 or O139, characterized by profuse watery diarrhea and rapid dehydration.
- Rehydration with oral rehydration solutions (ORS) is the cornerstone of treatment, with intravenous fluids reserved for severe dehydration.
- Vibrio species cause a range of infections, including cholera, gastroenteritis, wound infections, and sepsis, with Vibrio parahaemolyticus and Vibrio vulnificus being the most clinically significant.
- Antibiotic use is recommended for moderate-to-severe cases to shorten duration and reduce transmission, though resistance is increasing.
- Vaccination with oral killed vaccines (e.g., BivWC, WC-rBS) or live attenuated vaccines (e.g., Vaxchora) is recommended for travelers and outbreak settings.
1. DEFINITION & OVERVIEW¶
Cholera is an acute diarrheal disease caused by Vibrio cholerae serogroups O1 or O139, characterized by profuse watery diarrhea and rapid dehydration. It is a toxin-mediated illness due to cholera toxin (CT) and toxin-coregulated pilus (TCP). Other Vibrio species cause noncholera vibrioses, including gastroenteritis, wound infections, and sepsis.
Table 173-1: Assessing the Degree of Dehydration in Patients with Cholera¶
| DEGREE OF DEHYDRATION | CLINICAL FINDINGS |
|---|---|
| None or mild, but diarrhea | Thirst in some cases; <5% loss of total body weight |
| Moderate | Thirst, postural hypotension, weakness, tachycardia, decreased skin turgor, dry mouth/tongue, no tears; 5–10% loss of total body weight |
| Severe | Unconsciousness, lethargy, or "floppiness"; weak or absent pulse; inability to drink; sunken eyes (and, in infants, sunken fontanelles); >10% loss of total body weight |
Table 173-2: Treatment of Cholera, Based on Degree of Dehydration¶
| DEGREE OF DEHYDRATION | PATIENT’S AGE (WEIGHT) | TREATMENT |
|---|---|---|
| None or Mild, but Diarrhea | <2 years | 1/4–1/2 cup (50–100 mL) of ORS, to a maximum of 0.5 L/d |
| None or Mild, but Diarrhea | 2–9 years | 1/2–1 cup (100–200 mL) of ORS, to a maximum of 1 L/d |
| None or Mild, but Diarrhea | ‡10 years | As much ORS as desired, to a maximum of 2 L/d |
| DEGREE OF DEHYDRATION | PATIENT’S AGE (WEIGHT) | TREATMENT |
|---|---|---|
| Moderate | All ages and weights | Undertake IV fluid replacement with Ringer’s lactate (or normal saline). Give 100 mL/kg in the first 3-h period (or first 6-h period for children <12 months old); start rapidly, then slow down. Give a total of 200 mL/kg in the first 24 h. Continue until the patient is awake, can ingest ORS, and no longer has a weak pulse. |
1.1 Pathogenesis¶
Cholera toxin (CT) activates adenylate cyclase, increasing intracellular cyclic AMP (cAMP) and promoting chloride and sodium secretion into the intestinal lumen. This leads to isotonic fluid loss, resulting in severe dehydration. The toxin-coregulated pilus (TCP) facilitates bacterial colonization of the small intestine.
1.2 Clinical Spectrum¶
Clinical manifestations range from asymptomatic carriage to severe cholera gravis (life-threatening dehydration). The characteristic 'rice-water' stool is due to isotonic fluid accumulation in the intestinal lumen.
2. EPIDEMIOLOGY¶
Cholera is endemic in regions with poor sanitation and limited access to clean water. Annual incidence rates vary by region, with >95% of reported cases in Africa and Asia. Risk factors include malnutrition, poor hygiene, and lack of access to safe water. Outbreaks often occur in displaced populations, war-torn areas, or after natural disasters.
Table 173-1: World Distribution of Cholera (2020–2022)¶
| Yearly Incidence Rate per 100,000 Inhabitants | Description |
|---|---|
| 0–0.1 | No reported case |
| 0.1–1 | Imported cases only |
| 1–10 | Low incidence |
| 10–100 | Moderate incidence |
| 100–1000 | High incidence |
2.1 Global Distribution¶
Cholera is native to the Ganges delta but has spread globally through seven pandemics since 1817. The seventh pandemic (El Tor biotype) began in Indonesia in 1961 and has since become endemic in Africa and Asia.
2.2 Demographics¶
Children <5 years are most affected globally, accounting for two-thirds of cases. In endemic areas, outbreaks often occur during "cholera seasons" linked to heavy rainfall and flooding.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Vibrio cholerae O1 and O139 are the causative agents of epidemic cholera. The toxin-coregulated pilus (TCP) facilitates colonization, while cholera toxin (CT) induces fluid secretion via adenylate cyclase activation. Horizontal gene transfer and quorum sensing regulate virulence gene expression.
Table 173-4: Electrolyte Composition of Cholera Stool and Intravenous Rehydration Solution¶
| SUBSTANCE | CONCENTRATI ON, mmol/L | NA+ | K+ | CL– | BASE |
|---|---|---|---|---|---|
| Stool | 135 | 15 | 100 | 45 | |
| Child | 100 | 25 | 90 | 30 | |
| Ringer’s lactate | 130 | 4a | 109 | 28 |
3.1 Toxin Mechanism¶
Cholera toxin (CT) consists of an enzymatic A subunit and a binding B subunit. The B subunit binds to GM1 gangliosides, allowing the A subunit to activate adenylate cyclase, increasing cAMP and promoting chloride and sodium secretion.
3.2 Virulence Factors¶
Key virulence factors include TCP, CT, and the ToxR regulatory system. Horizontal gene transfer of the CTX Φ bacteriophage and pathogenicity islands contributes to the evolution of toxigenic strains.
4. CLINICAL FEATURES¶
Clinical manifestations range from asymptomatic carriage to severe cholera gravis. Common symptoms include profuse watery diarrhea, vomiting, abdominal cramps, and dehydration. The characteristic 'rice-water' stool is due to isotonic fluid accumulation. Severe cases may present with hypovolemic shock and metabolic acidosis.
Table 173-5: Features of Selected Noncholera Vibrioses¶
| ORGANISM | VEHICLE OR ACTIVITY | HOST AT RISK | SYNDROME |
|---|---|---|---|
| Vibrio parahaemolyticus | Shellfish, seawater | Normal | Gastroenteritis |
| Vibrio parahaemolyticus | Seawater | Normal | Wound infection |
| Vibrio vulnificus | Shellfish | Immunosuppresseda | Sepsis, secondary cellulitis |
| Vibrio vulnificus | Seawater | Normal, immunosuppresseda | Wound infection, cellulitis |
4.1 Mild vs. Severe Disease¶
Mild cases present with watery diarrhea and mild dehydration. Severe cases (cholera gravis) involve rapid fluid loss (>250 mL/kg in 24 h), leading to hypovolemic shock, acidosis, and potential renal failure.
4.2 Complications¶
Complications include hypokalemia, metabolic acidosis, acute tubular necrosis, and toxic megacolon. Rectal prolapse and hemolytic uremic syndrome (HUS) are rare but possible complications.
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnoses include other bacterial infections (e.g., Shigella, Salmonella), viral gastroenteritis, parasitic infections (e.g., Giardia), and noncholera vibrioses. Noncholera vibrios (e.g., V. parahaemolyticus, V. vulnificus) may present with similar symptoms but have distinct clinical features.
5.1 Noncholera Vibrios¶
V. parahaemolyticus causes gastroenteritis and wound infections, while V. vulnificus is associated with severe sepsis, wound infections, and primary sepsis in immunocompromised patients.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis is confirmed by isolating V. cholerae from stool or using antigen detection tests. Stool cultures on TCBS agar or dark-field microscopy are used. WHO-recommended ORS is administered for rehydration. Antigen detection dipsticks are available for rapid field testing.
Table 173-3: Composition of WHO Reduced-Osmolarity ORS¶
| CONSTITUENT | CONCENTRATION, mmol/L |
|---|---|
| Na+ | 75 |
| K+ | 20 |
| Cl– | 65 |
| Citrate | 10 |
| Glucose | 75 |
6.1 Diagnostic Criteria¶
Cholera is suspected in patients with acute watery diarrhea in endemic areas or with severe dehydration. Confirmation requires isolation of V. cholerae O1 or O139 from stool.
7. MANAGEMENT & TREATMENT¶
Management includes aggressive rehydration with ORS or IV fluids, antibiotic therapy for moderate-to-severe cases, and treatment of complications. Zinc supplementation is recommended for children to reduce severity.
Table 173-2: Treatment of Cholera Based on Dehydration Severity¶
| DEGREE OF DEHYDRATION | PATIENT’S AGE (WEIGHT) | TREATMENT |
|---|---|---|
| None or Mild, but Diarrhea | <2 years | 1/4–1/2 cup (50–100 mL) of ORS, to a maximum of 0.5 L/d |
| None or Mild, but Diarrhea | 2–9 years | 1/2–1 cup (100–200 mL) of ORS, to a maximum of 1 L/d |
| None or Mild, but Diarrhea | ‡10 years | As much ORS as desired, to a maximum of 2 L/d |
| Moderate | All ages and weights | Undertake IV fluid replacement with Ringer’s lactate (or normal saline). Give 100 mL/kg in the first 3-h period (or first 6-h period for children <12 months old); start rapidly, then slow down. Give a total of 200 mL/kg in the first 24 h. Continue until the patient is awake, can ingest ORS, and no longer has a weak pulse. |
7.1 Rehydration¶
Oral rehydration is preferred unless the patient is comatose or in shock. ORS contains Na+, K+, glucose, and citrate. IV fluids (Ringer’s lactate) are used for severe dehydration.
7.2 Antibiotics¶
Antibiotics (e.g., azithromycin, doxycycline, ciprofloxacin) reduce duration and volume of diarrhea. Resistance is increasing, so susceptibility testing is recommended.
7.3 Complications¶
Toxic megacolon requires surgical intervention. Rectal prolapse is managed with manual reduction. HUS is treated with fluid restriction and hemodialysis.
8. PROGNOSIS & COMPLICATIONS¶
Mortality is low with prompt rehydration but can be high in untreated cases. Complications include hypokalemia, metabolic acidosis, acute renal failure, and toxic megacolon. Severe cases may lead to hypovolemic shock and death.
8.1 Mortality¶
Mortality is <1% with adequate rehydration but can exceed 50% without treatment. Severe cases in immunocompromised patients (e.g., V. vulnificus) have higher mortality.
9. SPECIAL CONSIDERATIONS¶
Vaccination with oral killed vaccines (e.g., BivWC, WC-rBS) or live attenuated vaccines (e.g., Vaxchora) is recommended for travelers and outbreak settings. Zinc supplementation reduces severity in children. Safe water and sanitation are critical for prevention.
9.1 Vaccination¶
Oral vaccines (BivWC, WC-rBS) provide ~60–85% protection. Vaxchora (live attenuated) is approved for travelers. Vaccination is part of WHO's global cholera control strategy.
9.2 Zinc Supplementation¶
Oral zinc (10–20 mg/day for 10 days) reduces severity and duration of diarrhea in children <60 months.
10. KEY POINTS & CLINICAL PEARLS¶
- Rehydration with ORS is the cornerstone of cholera management. 2. Antibiotics reduce duration but are not always necessary. 3. Vaccination is critical in endemic areas and outbreak settings. 4. Zinc supplementation improves outcomes in children. 5. Prevention relies on safe water, sanitation, and hygiene.