JAPANESE ENCEPHALITIS

KEY POINTS

1. Because JE is a usually sporadic, but occasionally epidemic, disease, vaccination is to be considered for JE destination countries when any of these pertain,

a. Substantial or prolonged visits

b. Disease activity is spiking at epidemic level

c. Rural travel (prolonged, recurrent)

2. If it has been several years since vaccination was completed, a blood test for persistent, sufficient immunity (JE IgG antibody) can be performed. If antibody level is too low, a vaccine booster is recommended for ongoing disease exposure.

3. JE virus is transmitted by mosquitoes, so skin barrier measures (repellents, clothing) can reduce risk.

Disease:  A central nervous system infection by Japanese encephalitis virus (JEV) causing brain inflammation (encephalitis).  It is usually asymptomatic, but overt encephalitis may bring,

  1. Residual neurological damage/psychiatric dysfunction = 50%

  2. Death = 30%

Symptoms:

  1. Fever

  2. Headache

  3. Nausea

  4. Confusion/Behavioral Changes

  5. Seizures

  6. Coma

Prevalence:  Southeast Asia, Western Pacific, Eastern Russia, and northern Australia. JEV is present in rural, agricultural areas, especially where flooding irrigation (rice fields) is used. Highest risk is May – September, but JEV is year-round in many countries. The risk of JEV is very low for most travelers.

Transmission: Culex  mosquitoes, especially at dusk and dawn

Treatment: None

Prevention: Risk correlates with,

  1. Prolonged or frequent stays in rural areas.

  2. Exposure in an epidemic.

  3. Extensive outdoor activities.

  4. Vaccine (IXIARO; killed) .

    a. Schedule: doses, on day “0” and day 28; optimally complete at least a week prior to exposure.

    b. Booster doses: possibly 1 – 2 years after primary vaccine

    c. Duration of immunity is unknown, but can be checked with blood tests (turnaround time averages 10 – 14 days).

    d. Vaccine (IXIARO) is for > 17 yrs of age.

  5. Targets,

    a. Travelers in endemic areas > 1 month during JEV season; also for short-term travelers if going outside urban areas

    b. Travelers entering a JEV disease outbreak

    c. Travel to endemic areas with extensive outdoor exposure

    d. Expatriates or recurrent travelers to JEV endemic areas

  6. Side-Effects

    a. Common (25%): Injection site pain, swelling

    b. Systemic (20%): Usually mild, including headache, muscle aches, fatigue, flu-like illness

  7. Precautions/Contraindications

    a. Hypersensitivity to protamine sulfate

    b. Safety and effectiveness not established in pregnant/nursing women or immune-compromised.

  8. Other Preventive Measures,

    a. Stay in well-screened and air-conditioned areas.

    b. Maximal clothing coverage of exposed skin

    c. Insect repellents with DEET

    d. Bed nets

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