What are the recommended prophylaxis measures for typhoid and leptospirosis?

Prophylaxis for Typhoid and Leptospirosis

Typhoid Prophylaxis

For typhoid fever, vaccination is the primary prophylactic measure, with two widely available vaccines offering 50-80% protection: the oral live-attenuated Ty21a vaccine (four capsules over 7 days) and the injectable Vi polysaccharide vaccine (single 0.5 mL dose). 1

Who Should Receive Typhoid Vaccination

• Travelers to endemic areas: Vaccination is recommended for those traveling to developing countries in Latin America, Asia, and Africa, particularly with prolonged exposure to potentially contaminated food and water 2
• Laboratory workers: Microbiologists and others who frequently work with S. Typhi should be vaccinated, as seven laboratory-acquired cases occurred during 1985-1994 1
• Household contacts: Persons with intimate exposure to documented typhoid carriers, including continued household contact, should receive vaccination 2

Vaccine Options and Administration

Oral Ty21a Vaccine (Vivotif)

• Dosing: One enteric-coated capsule taken on alternate days for a total of four capsules, with cool liquid no warmer than 37°C, approximately 1 hour before meals 2
• Efficacy: Prevents approximately 50% of typhoid cases during the first three years after vaccination (cumulative efficacy 50%, 95% CI 35-61%) 3
• Boosters: Revaccination with the entire four-dose series every 5 years 1, 2
• Age restriction: Approved for adults and children ≥6 years 2
• Contraindications: Should not be used in immunocompromised persons, including those with HIV infection 1, 2
• Drug interactions: Avoid concurrent antimicrobials (including antimalarial chemoprophylaxis), and wait at least 72 hours after completing antibiotics before administration 1, 4

Injectable Vi Polysaccharide Vaccine

• Dosing: 0.5 mL subcutaneously or intramuscularly as a single dose for adults and children ≥10 years 2
• Efficacy: Prevents approximately 69% of typhoid cases in year 1 (95% CI 63-74%) and 59% in year 2 (95% CI 45-69%) 3
• Boosters: Every 2-3 years under conditions of continued or repeated exposure 1, 2
• Age flexibility: Can be given to children 6 months to <10 years at 0.25 mL subcutaneously on two occasions separated by ≥4 weeks 2

Critical Limitations and Precautions

• Vaccination is not a substitute for careful food and water selection, as vaccines are not 100% effective and protection can be overwhelmed by large bacterial inocula 2, 4
• Both vaccines have low complication rates, with serious adverse events requiring hospitalization occurring in 0.47 to 1.3 per 100,000 doses 1
• No vaccines protect against paratyphoid fever caused by Paratyphi A, which is increasing in incidence with antimicrobial resistance 1

Antibiotic Prophylaxis

Ciprofloxacin can be used for typhoid fever treatment at 500 mg orally every 12 hours for 10 days, but is not recommended for routine prophylaxis due to increasing fluoroquinolone resistance, particularly among travelers to South and Southeast Asia 5, 1

• Resistance to nalidixic acid (a marker for decreased ciprofloxacin susceptibility) increased from 19% in 1999 to 59% in 2008 1
• Antibiotic prophylaxis should be reserved for treatment of confirmed cases rather than prevention 5

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Leptospirosis Prophylaxis

No vaccine for leptospirosis is currently available in the United States or most developed countries, making prophylaxis primarily dependent on behavioral measures and, in specific high-risk situations, antibiotic chemoprophylaxis.

Primary Prevention Measures

• Avoid exposure to contaminated water and soil, particularly in endemic areas during flooding or after natural disasters
• Use protective clothing and footwear when occupational or recreational exposure to potentially contaminated water is unavoidable
• Control rodent populations in residential and occupational settings to reduce environmental contamination

Antibiotic Chemoprophylaxis

Doxycycline 200 mg orally once weekly is the standard chemoprophylactic regimen for high-risk exposures, though this is based on limited evidence and is not routinely recommended for travelers.

• Chemoprophylaxis should be considered for:
  • Military personnel or occupational groups with unavoidable high-risk water exposure in endemic areas
  • Short-term travelers with anticipated high-risk water activities in outbreak settings
  • Post-exposure prophylaxis after significant contaminated water exposure

Important Caveats

• No evidence from the provided guidelines specifically addresses leptospirosis prophylaxis, indicating this remains an area without strong guideline support
• The decision to use antibiotic prophylaxis must weigh the risk of exposure against potential adverse effects and the development of antibiotic resistance
• Prophylaxis does not replace the need for prompt medical evaluation if symptoms develop after potential exposure