JAPANESE ENCEPHALITIS
 
How JE is Diagnosed?

Clinical:

Clinically JE cases present signs and symptoms similar to encephalitis of viral origin and cannot be distinguished for confirmation. However, JE can be suspected as the cause of encephalitis as a febrile illness of variable severity associated with neurological symptoms ranging from headache to meningitis or encephalitis. Symptoms can include headache, fever, meningeal signs, stupor, disorientation, coma, tremors, paralysis (generalized), hypertonia , loss of coordination.

Laboratory:

Several laboratory tests are available for JE virus detection which include;

  • Antibody detection: Heamagglutination Inhibition Test (HI), Compliment Fixation Test (CF), Enzyme Linked Immuno-Sorbant Assay (ELISA) for IgG (paired) and IgM (MAC) antibodies, etc.
  • Antigen Detection: RPHA, IFA, Immunoperoxidase etc.
  • Genome Detection - RTPCR
  • Isolation - Tissue culture, Infant mice, etc
  • In view of the limitations associated with various tests, IgM ELISA is the method of choice provided samples are collected 3-5 days after the infection.
Case definitions for JE Diagnosis and Reporting:

Clinical Suspect

Febrile illness of variable severity associated with neurological symptoms ranging from headache to meningitis or encephalitis. Symptoms can include headache, fever, meningeal signs, stupor, disorientation, coma, tremors, paralysis (generalized), hypertonia , loss of coordination.

(Patient with fever, altered sensorium lasting more than 6 hours, no skin rash and other known causes of encephalitis excluded)


Probable

A suspected case with presumptive laboratory results: Detection of an acute phase anti-viral antibody response through IgM in serum/ elevated and stable JE antibody titres in serum through ELISA/HI/Neutralising assay.

Confirmed

A suspect case with confirmed laboratory result : JE IgM in CSF or 4 fold or greater rise in paired sera (acute & Convalescent) through IgM/IgG ELISA, HI, Neutralisation test or detection of virus, antigen or genome in tissue, blood or other body fluid by immuno-chemistry, immunoflourescence or PCR.