JAPANESE ENCEPHALITIS VIRUS

Structure & Property	Transmission	Pathogenesis	Clinical findings	Laboratory diagnosis	Treatment	
Family: flavivirus

Genome: single-strand RNA, +ve polarity.

Size: 40-50nm

Icosahedral nucleocapsid.

Enveloped virion

One serotype

Antigenically related to dengue viruses	Transmitted to humans by certain species of Culex mosquito endemic to Asian rice fields.

Two main reservoir hosts: humans and pigs.	Infection follows bite by infected mosquito.

Virus replicates locally either in skin, lymphatics or endothelium of blood vessels.

Transient viraemia.

Virus enters nervous system:
- by capillary seeding through endothelium into meninges and brain.
- infection of nerve endings with subsequent axoplasmic transport to neurons.

Destruction of neurons & glial cells, perivascular inflitration with lymphocytes, focal hemorrhages.	Most common cause of epidemic encephalitis.

Abrupt onset with fever, headache, malaise, drowsiness, vomiting & generalized convulsions.

Marked and increasing disturbances of sensorium & signs of meningeal irritation.

CSF abnormalities: pleocytosis, elevated glucose and protein content.

Mortality:
- <10% in endemic areas
- 20-50% in severe epidemics.

Neurological sequelae:
- motor weakness
- mental backwardness
- behavior disorders	Diagnosis:
- haemagglutiation-inhibition for rise in antibody titer.
- IgM and IgG ELISA 

IgM produced in CNS during encephalitis, appears in CSF	Japanese encephalitis vaccine:
- inactivated virus in mouse brain
- in three doses subcutaneously.
- recommended for travelers to endemic areas in Far East and Southeast Asia.

Pesticides to control mosquito vector.