This document discusses Japanese encephalitis (JE), a mosquito-borne viral disease prevalent in parts of Asia and the Pacific. It notes that JE is a zoonotic disease, with pigs acting as an amplifying host and birds and animals as natural reservoirs. While most human cases are asymptomatic, some progress to severe encephalitis, coma, and even death. Diagnosis involves testing blood or cerebrospinal fluid for JE-specific IgM antibodies or viral RNA. There is no treatment other than supportive care, so prevention through mosquito control and vaccination are important for those at risk of exposure.

1. Dr. Arifa Akram Barna
MBBS , M.D (Virology)
Medical Officer
Department of Virology
IEDCR,DGHS,DHAKA.

2. • Japanese encephalitis (JE) - mosquito-borne viral
disease (zoonotic)
• First detected in Japan in 1870
• Humans become infected coincidentally when come in
close proximity to JE infected animals and birds.

3. • Japanese encephalitis (JE) is prevalent in Asia, Southeast
Asia, East Asia, and the Pacific.
• In endemic areas-
3 billion people are at risk
Incidence of 30,000–50,000 cases and 10,000–15,000
death
• The incidence of JE is increasing in –
Bangladesh, Cambodia, Indonesia, Laos, Myanmar, North Korea,
and Pakistan
• The incidence of JE is decreasing in -
Japan and South Korea.

4.  Location –
Rural areas (mostly)
Around the cities
 Seasonality –
Following monsoon
Japanese encephalitis sero-surveillance program
exist in Bangladesh since 2008

5.  Genus: Flavivirus
 Virions: Spherical, lipoprotein-enveloped
particles being 40-50nm in diameter,
 Genome: Single stranded positive sense RNA
 Incubation period: 4-14 days
 Modes of transmission
Transmitted by bite of infected Culex mosquitoes.
No person-person or animal-person transmission.

6. Natural reservoirs:
wild and domestic birds, and pigs
Host: human and horse.
Amplifying Host:
Pigs act as amplifying host maintaining high level of
viraemia.
“Humans are vulnerable to this disease and this
disease is a primary public health concern in Asia;
humans are considered a dead-end host”

9. {RESERVOIR HOST}

10. 10
Environment
Vector Mosquito
Host - Amplifying Host - Carrier
Victim-Accidental
Full Recovery DeathRecovery with
residual
complications

12.  Mostly asymptomatic
 Often develop mild disease
◦ Fever
◦ Chills and bodyaches
◦ headache
◦ leads to an uneventful recovery
 some cases rapidly progress to severe encephalitis with mental
disturbances, general or focal motor abnormalities with
◦ signs of meningism (neck rigidity, Kernig’s sign), particularly in adults
◦ abdominal pain and convulsions (due to encephalitis) in pediatric patients
 Progressive coma and death in few cases

14. Specimens:
Venous Blood for serum
On admission
On discharge / 10th
day of illness/death
Cerebrospinal fluid (CSF)
Tests:
 IgM-capture (MAC) – ELISA (recommended test)
 70-75% of patients have JE specific IgM antibody - 4 days after
onset. 100% patients will have antibody 7-10 days after onset.

15.  Plaque Reduction Neutralization Test (PNRT)
 RT-PCR
 Virus Isolation

16. IgM-capture (MAC) – ELISA
Substrate Colored
compound

17. Calculate the mean JE Negative Control values with JERA and with the Control antigen:
Example: JE Negative Control
OD
JERA NCA
No 1 -0.188 0.066
No 2 -0.192 0.061
Total 0.380 0.254
Averages (JERA) = 0.380 ÷ 2 = 0.190 & (NCA) = 0.254 ÷ 2 = 0.127
Calculate the JERA/NCA ratio: 0.190 ÷ 0.127 = 1.50
Any JE Negative Control JERA/NCA ratio greater than 2.8 indicates that the test procedure must be
repeated.
Calculation of the Positive Control:
Calculate JE IgM Positive Control values with JERA and with the NCA.
Example: JE IgM Positive Control
OD
JERA NCA
No 1- 1.035 0.105
No 2- 1.055 0.115
Total 2.090 0.220
Averages (JERA) = 2.090 ÷ 2 = 1.045 & (NCA) = 0.220 ÷ 2 = 0.110
Calculate the JERA/NCA ratio: 1.045÷ 0.110 = 9.5
Any JE IgM Positive Control JERA/NCA ratio less than 6.0 indicates that the test procedure must be
repeated.

18. • No effective treatment
• Supportive Care:
- Antipyretics
- Anticonvulsants
- Maintenance of Nutrition
- Treatment of Secondary
Bacterial Infection

19.  Personal protective measures and
mosquito elimination are the most
important
 Travellers going to endemic areas
may consider vaccination
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20. •First in1930
inactivated mouse brain-derived vaccine (the Nakayama and/or
Beijing-1 strain and JE-VAX, until production ceased in 2005.
• Live-attenuated ChimeriVax-JE (marketed as IMOJEV)
A single dose of this chimeric JE vaccine was found to be safe,
highly immunogenic and capable of inducing long lasting immunity
in both preclinical and clinical trials.
•The primary two doses are administered 4 weeks apart. A booster
dose is recommended 1–2 years after the primary immunization

21. 21
•Wear light-coloured, long-sleeved clothing and
trousers
•Apply DEET(N,N-Diethyl-meta-toluamide )-
containing mosquito-repellents over exposed
parts of the body and clothes every 4 to 6 hours
(DEET was historically believed to work by blocking insect
olfactory receptors)

22.  Put all used cans and bottles into
covered dustbins
 Change water for plants at least
once a week, leaving no water in
the saucers underneath flower
pots
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23.  Keep all drains free from
blockage
 Cover tightly all water
containers, wells and water
storage tanks
 Top up all defective ground
surfacers to prevent the
accumulation of stagnant
water
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24.  History of previous severe allergic reaction
 Infant< 1yr of age
 Pregnancy
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