JE disease manifestations can be divided into three stages.
Prodromal Stage :
is characterised by
- Fever
- Rigors
- Headache
- Nausea
- and Vomiting
The Prodromal stage usually lasts for 1 to 6 days. It can be as short as less than 24 hours or as long as 14 days.
An Acute Encephalitic Stage:
Begins by the third to fifth day. The symptoms include:
- Convulsions
- Altered sensorium, unconsciousness, coma
- Mask like face
- Stiff Neck
- Muscular Rigidity
- Tremors in fingers, tongue, eyelids and eyes.
- Abnormal movements of limbs
- Speech impairment
A Late Stage:
Characterised by
- the persistance of signs of CNS injury such as,
- Mental impairment.
- Increased deep Tendon reflexes
- Paresis either of the upper or lower motor neuron type.
- speech impairment
- Epilepsy, Abnormal movements, Behaviour abnormalities.
Diagnosis of JE involves
Detection and Isolation of Virus
Collection of Specimens:
- CSF (Cerebro Spinal Fluid)
- Blood
Collection of CSF:
- CSF can be collected by Lumbar puncture from the suspected cases during the early acute phase.
- Collected specimens must be stored at 4 C on dry ice and transposrted to laboratory.
Collection of CSF from Dead Patients:
-
Smal brain tissues can be collected from different parts of the brain - cerebral crotex, cerebellum, basal nuclei and brain stem.
- Small pieces of brain tissues can be obtained by biobsy, using a VIM-Silverman needle inserted via the nose through the cribriform pate of the ethmoid bone.
- The brain tissues should be immersed in 2ml of 10% glecerol-saline (pH 7.4)
- Specimens for virus isolation should be transported in sealed containers in dry ice or liquid nitrogen.
Collection of Blood
-
Blood specimens should be collected from suspected JE cases in the acute phase
- A second, convalescent specimen should be collected after 2-4 weeks.
- Venous blood is collected aseptically, kept at room temperature for 15 min, to clot, then kept at 4c for one hour.
- The serum has to be seperated from the clot and stored in sterile container at 4;c
Detection and Isolation of Virus
- Detection of Antigen
- Detection of Antibody
Detection of Antigen from CSF
1. Immunofluorescent Assay (IFA)
- For detection of JEV antigen in CSF as early as the second day of illness.
- JE Antigen can be detected using immunoperoxidase
- When IgM antibodies are not detected in the CSF IFA is useful.
2. Reverse passive Haemagglutination (RPHA) test
RPHA is valuable if CSF samples are obtained within 10 days of onset of clinical symptoms.
Monoclonal Antibodies are used that are directed against envelope glycoprotein (V3) of JEV
RPHA is capable of detecting free antigen as well as antigen complexed with antibodies.
JE virus genome can be detected using the Polymerase Chain Reaction (PCR) for blood of CSF specimens collected from the acute stage.
- Virus isolation can be achieved by inoculation of specimens into infant mice.
Detection of Antibody from Serum
All the above tests are based on the rise of IgG antibody titre in paired sera collected at an interval of 15-20 days.
Detection of Antibody from Serum and CSF
IgM captured Enzyme Linked Immunosorbant Assay (MAC ELISA):
- IgM antibodies to JEV in the CSF and Serum can be detected using conjugated anti IgM
- IgM antibodies are present in all cases beyond the seventh day of illness.
- MAC ELISA is advantageous in providing diagnosis with a single specimen of CSF.
- The cross reactivity with other closely related flaviviruses is negligible.
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