Japanese Encephalitis IgM among Patients with Acute Encephalitis in Karachi, Pakistan –Implications of Laboratory Diagnostic Results

Abstract

Japanese encephalitis (JE) is a mosquito-borne illness and a major cause of viral encephalitis in southern Asia and Southeast Asia. Infection is symptomatic in less than 1% of all infected cases. Past studies from the 1980s identified JE as an infrequent cause of viral encephalitis in Pakistan. We conducted Enzymelinked immunosorbent assay (ELISA) based laboratory testing for Japanese encephalitis IgM in cerebrospinal fluid (CSF) and serum samples among patients with acute encephalitis presenting to a tertiary care hospital in Karachi, Pakistan. Among 117 patients hospitalized with encephalitis of unknown etiology at the Aga Khan University Hospital whose sera or CSF were tested, 4 (n=4; 3.4%) were positive for JE IgM. Further testing of the samples against dengue and West Nile IgM is warranted to ensure whether these are true positive cases of JE or crossreactive with other flaviviruses.