Cholera Carrier State

Cholera carrier state is the shedding of toxigenic Vibrio cholerae O1 or O139 in stool by a person with no symptoms (asymptomatic infection) or after recovery (convalescent carriers). Most infections are asymptomatic or mild; only about 1 in 10 infected people develop severe watery diarrhoea.

• Asymptomatic carriers and convalescent carriers excrete vibrios for up to 2 weeks; rarely chronic biliary carriers shed for months or years in association with gallbladder disease.
• Carriers sustain transmission through food handling and poor sanitation.

No symptoms, or mild diarrhoea; asymptomatic infection is discovered by contact tracing or stool culture.

• Chronic carriers may have recurrent right upper quadrant discomfort or gallstones.
• Differential diagnosis: other causes of carriage (non toxigenic V. cholerae non O1), enterotoxigenic E. coli, rotavirus and other diarrhoea, gallbladder disease.
• Complications: transmission to contacts and outbreaks, development of clinical cholera in household contacts, chronic gallbladder carriage.

Laboratory identification of the organism.

• Stool or rectal swab culture on thiosulfate citrate bile salts sucrose agar with serotyping, or PCR for ctxA gene; rapid antigen test for screening.
• Three consecutive stool cultures 24 hours apart, taken at least 48 hours after antibiotics, to prove clearance.
• Gallbladder ultrasound and bile culture in chronic carriers.

Reduce shedding and prevent onward transmission.

• Supportive: oral rehydration solution for any diarrhoea, exclusion of carriers from food handling, childcare and healthcare work until clearance, hand washing with soap, safe water (chlorination at 0.5 mg/L free residual), safe disposal of faeces, food hygiene, health education.
• Pharmacological: single dose azithromycin 1 g orally (children 20 mg/kg, maximum 1 g), or doxycycline 300 mg single dose (adults, not for pregnant women or children under 8 years), or ciprofloxacin 1 g single dose (adults); alternative tetracycline 500 mg four times daily for 3 days. Close household contacts of cases: a single dose of azithromycin or doxycycline as chemoprophylaxis. Oral cholera vaccine 1.5 mL orally, 2 doses at least 14 days apart (a single dose during outbreaks), from 1 year of age. Zinc 20 mg daily for 10 days in children with diarrhoea.
• Procedures: cholecystectomy for chronic biliary carriers with gallstones, after antibiotic treatment.
• Special groups: pregnancy, azithromycin 1 g single dose (avoid doxycycline and ciprofloxacin); children, azithromycin 20 mg/kg; HIV, give azithromycin 1 g as a single dose and watch closely for dehydration; food handlers, culture clearance before return.
• Red flags: any watery diarrhoea (convert to case management), vomiting, dehydration, rapid onset in household contacts.
• Follow-up: repeat stool cultures after treatment (three negatives), notify the public health authority, contact tracing, community water and sanitation measures.