Japanese Encephalitis Flashcards
1
Q
What is the family?
A
Flavivirus
2
Q
How many serotype?
A
1
3
Q
How is it related to dengue viruses?
A
Antigenically related
4
Q
Describe the pathogenesis
A
- Infection follows bite by infected mosquito
- Virus replicates locally either in skin, lymphatics or endothelium of blood vessels
- Transient viraemia
- If viraemia terminates before virus penetrates brain/destroys sufficient brain cells to produce overt encephalitis, infection will be asymptomatic/merely a non-encephalitic generalised febrile illness
5
Q
How does it enter the nervous system?
A
- Capillary seeding through endothelium into meninges and brain
- Infection of nerve endings with subsequent axoplasmic transport to neurons
6
Q
Who is the vector, amplifying and incidental host?
How is it transmitted?
A
Mosquitoes - Culex tritaeniorhynchus, Culex gelidus (vector)
Pigs/birds (amplifying hosts)
Man (incidental host)
Transmitted in an enzootic cycle among mosquitoes and vertebrate hosts
7
Q
What are the clinical presentations?
A
- Abrupt onset with fever, headache, malaise, drowsiness, vomiting and generalised convulsions
- Marked and increasing disturbances of sensorium and signs of meningeal irritation (neck rigidty, positive Kernig’s sign)
- CSF abnormalities: pleocytosis, elevated glucose content, raised protein
- Sequelae common in surviving patients: motor weakness, mental backwardness, behaviour disorders (apathy, aggressiveness)
8
Q
What does histopathology of brain show?
A
Destruction of neurons and glial cells, perivascular infiltration with lymphocytes, sometimes focal haemorrhage
9
Q
How to diagnose?
A
- IgM capture ELISA (IgM produced in CNS during encephalitis and appears in CSF)
- RT-PCR
10
Q
How to prevent and control?
A
Inactivated/live attenuated vaccines in some countries
