Japaneese encephalitis

Dr. Arifa Akram BarnaMBBS , M.D (Virology)

Medical OfficerDepartment of Virology

IEDCR,DGHS,DHAKA.

• 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.

• 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.

Location –Rural areas (mostly)

Around the cities Seasonality –

Following monsoon

Japanese encephalitis sero-surveillance program exist in Bangladesh since 2008

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.

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”

{RESERVOIR HOST}

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EnvironmentVector Mosquito

Host - Amplifying Host - Carrier

Victim-Accidental

Full Recovery DeathRecovery with residual

complications

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  

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.

Plaque Reduction Neutralization Test (PNRT)

RT-PCR

Virus Isolation

IgM-capture (MAC) – ELISA

Substrate Colored compound

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

• No effective treatment

• Supportive Care:- Antipyretics

- Anticonvulsants- Maintenance of Nutrition- Treatment of Secondary

Bacterial Infection

Personal protective measures and mosquito elimination are the most important

Travellers going to endemic areas may consider vaccination

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•First in1930inactivated 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

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•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)

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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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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History of previous severe allergic reaction Infant< 1yr of age Pregnancy

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