Objective: To determine the viral agent involved in cases of acute encephalopathy in children during an outbreak in Northern India.
Design: Virological and serological studies using serum and cerebrospinal fluid specimens from patients.
Methods: Serum and CSF specimens were tested by IgM ELISA for IgM antibodies to variety of viruses like Japanese encephalitis, West Nile, Dengue and Measles. The specimens were inoculated into Vero cell monolayer for virus isolation. The viral strains isolated were identified by indirect immunofluorescence test and qualitative in-vitro neutralization test using polyclonal and monoclonal antibodies to measles. Identity of the isolates was reconfirmed using RT-PCR method.
Results: Of the 28 specimens tested, 17 had IgM antibodies to measles. Commercial IgM ELISA kits confirmed the serological findings. Vero cell cultures yielded 4 isolates from CSF and 2 from serum specimens of six different patients. Cytopathic effect was typical of measles. Indirect imunofluorescence using polyclonal and monoclonal antibodies to measles HA protein, confirmed the measles etiology. Neutralization tests reconfirmed the measles strain isolation. RT-PCR amplified product was confirmed as measles.
Conclusion: The isolation of measles virus from CSF and serum of children with acute encephalopathy without rash proved the etiological role of measles virus in this outbreak.