Japanese Encephalitis

Travel Guide Travel Health Japanese Encephalitis

Introduction

Japanese Encephalitis (JE) is a viral disease and is transmitted by the (Culex) mosquito. It is a member of the Flaviviridae family of viruses which are also responsible for West Nile Virus, Yellow Fever, Dengue Fever, among others. Japanese Encephalitis is a preventable disease. The virus is prevalent throughout Asia and cases have been reported from the Torres Strait Islands. The disease has not been identified in Africa, Europe, North America or South America. Cases reported in these areas are considered to be travel-related only.^[1]

Japanese Encephalitis is predominantly found in rural agricultural areas where flood irrigation of crops is most commonly practiced. Areas which combine flood irrigation and pig farming have also seen a rise in the number of disease cases. Urban areas can see an increase in the number of infections depending on the amount of percipitation and duration of the rainy season. Approximately 30,000-50,000 cases of JE are reported to the World Health Organization (WHO) yearly.^[1]^[2]

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Prevention

Japanese Encephalitis vaccinations*
When outdoors, use insect repellent containing 35% DEET for adults and 10% DEET for children. Follow the directions on the package.
Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.
Avoid wearing dark coloured clothing.
Avoid wearing perfume/cologne and scented cosmetics.

*Vaccinations are recommended for travelers planning to visit rural/agricultural areas for extended periods and people planning to live in endemic/epidemic areas.^[1]

Pre-Exposure Vaccinations

Pre-exposure prophylaxis is a series of three vaccinations given at 0, 7 and 30 days. The third injection can be given at 14 days though effectiveness will be lessened by the shorter interval. Shorteneing the intervals is only recommended in unusual circumstances. The final injection should be given at least 10 days prior to scheduled travel. Vaccinations should not be given to children under one year of age as no safety information is available at this time. Boosters are administered every 2-3 years. Those receiving the 30 day regimen can expect up to 90% protection while those receiving the 14 day regimen can expect approximately 80% immunity to the infection.^[1]^[3]

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Symptoms and Treatment

Symptoms

As stated above, 30,000-50,000 cases of JE are reported to WHO every year - these cases all having symptoms identifable to the disease. It is estimated that only 1 of every 200-250 cases will develop clinical signs of the infection while the remainder are either asymptomatic or suffer from headache and/or mild fever which go undiagnosed as JE. The incubation period is between 5 and 15 days in duration.

Encephalitis (swelling of the membrane surrounding the brain) is the most common symptom which presents with headache, blurred vision, altered mental state, and/or behavioral changes. Generalized weakness and compromised limb movement can also appear. Upset stomach and gastrointestinal distress may present early in the infection. Seizures in small children are common.

Japanese Encephalitis is hard to identify in the early stages of infection. It can easily be confused with many other illnesses (influenza, malaria, hepatitis, typhoid, etc.) and laboratory analyses are required to confirm the diagnosis.^[1]

Treatment

At this time there are no specific treatments for JE. Those requiring medical attention will be treated symptomatically. Receiving the vaccine and using preventative measures against mosquitoes are the best defenses.

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