Diagnosis of Nipah virus encephalitis by electron microscopy of cerebrospinal fluid

Background: between 1998 and 1999, an outbreak of potentially fatal viral e ncephalitis erupted among pig farm workers in West Malaysia, and later spre ad to Singapore where abattoir workers were afflicted. Although Japanese en cephalitis virus was initially suspected, the predominant aetiologic agent was subsequently confirmed to be Nipah virus, a novel paramyxovirus related to but distinct from Hendra virus. Objective: to describe a case of Nipah virus encephalitis in a pig farm worker from Malaysia. Study design: the cl inical, laboratory and radiological findings of this patient were scrutiniz ed. Special emphasis was placed on the electron microscopic analysis of the cerebrospinal fluid (CSF) specimen from this patient. Results the neurolog ical deficits indicative of cerebellar involvement were supported by the ma gnetic resonance imaging that showed prominent cerebellar and brainstem les ions. CSF examination provided further evidence of viral encephalitis. Comp lement fixation and/or RT-PCR assays were negative for Japanese encephaliti s, herpes simplex, measles and mumps viruses. ELISA for detecting IgM and I gG antibodies against Hendra viral antigens were equivocal for the CSF spec imen, and rested initially negative for the first serum sample but subseque ntly positive for the repeat serum sample. Transmission electron microscopy of negatively-stained preparations of CSF revealed enveloped virus-like st ructures fringed with surface projections as well as nucleocapsids with dis tinctive helical and herringbone patterns, features consistent with those o f other paramyxoviruses, including Hendra virus. Conclusion: this case repo rt reiterates the relevant and feasible role of diagnostic electron microsc opy for identifying and/or classifying novel or emerging viral pathogens fo r which sufficiently specific and sensitive tests are lacking. (C) 2000 Els evier Science B.V. All rights reserved.