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DHS information: www.dhs.vic.gov.au/phb/
Overseas information: http://www.cdc.gov/travel/jenceph.htm

Japanese Encephalitis

Japanese B encephalitis, an uncommon but serious infection, is endemic throughout most of the Far East and South East Asia. Symptoms include headache, reduced consciousness, spacticity and fits.The incubation period is between 5 to 15 days

The case fatality rate in epidemics is 10-50%, and about half the survivors are left with neurological damage. Children and the elderly have a significant higher incidence of complications. The causal virus is transmitted by rice field breeding mosquitoes. Pigs, horses and wild birds are the amplifier hosts. The proximity of pigs to humans increases the chance of transmission.

Immunisation in humans is the only practicable way to prevent disease, and vaccine is available. Protective efficacy is 95%. Some authorities claim that the vaccine provides some protection against Dengue but evidence of this is unreliable.

More recently Japanese Encephalitis has become established in Papua New Guinea and the Torres Strait Islands with sporadic cases  in Northern Australia

Distribution of Japanese B encephalitis:
1 . Epidemic areas

• annual outbreaks of 4 - 5 months at the end of the wet season in late Summer and Autumn (April to November) with peak transmission in May-June.
• in temperate regions and northern part of tropical zones in: Bangladesh ,Japan, Nepal, Burma (northern), Kampuchea, Thailand (north-Chiang Mai area), Korea, Vietnam, China (except Xinzang/Tibet, Xinjiang/Sinklang and Qinghai), India (northern), Laos, eastern areas of Russia.

2. Endemic areas

• Sporadic cases occur throughout the year.
• in tropical areas of: Indonesia, Philippines, South India , Laos, Singapore, Taiwan, Malaysia, Sri Lanka, south Thailand, India (in particular West Bengal, Uttar Pradesh, Andhra Pradesh, Bihar, Karnataka and Assam), lowlands of Nepal.
• In subtropical and tropical areas, risk is present throughout the year, but is accentuated during rainy season and early dry season when mosquito populations are higher.

3. Indications for Use
The old vaccine availability was restricted in 1991 due to a high incidence of allergic reactions, but it is now believed that these related to certain batches of the vaccine. The new vaccines are much safer.

Vaccination is recommended for travellers spending more than 4 weeks in rural areas of Asia, particularly if travel is during the wet season, and/or there is considerable outdoor activity and/or the standard of accommodation is suboptimal. Vaccination is also recommended for expatriates spending a year or more in Asia (excluding Singapore) even in urban areas.
(  p 47. Australian Immunisation Handbook, 8th Edition 9/2003 &  Part 3.12, 'Japanese encephalitis').

4. New Vaccines

(a) JESPECT (called 'Ixiaro' overseas) - approved product information

• registered for children 18 years old and above
• 2 injections 28 days apart (currently approx $130/dose)