BACKGROUND Serological evidence of
West Nile virus (WNV)
infection has been reported in different regions of
Brazil from equine and
human hosts but the
virus had never been isolated in the country. OBJECTIVES We sought to identify the viral
etiology of
equine encephalitis in Espírito Santo
state.
METHODS We performed viral
culture in C6/36
cells, molecular
detection of WNV
genome, histopathology and
immunohistochemistry from
horse cerebral
tissue. We also carried out sequencing,
phylogenetic analysis and molecular clock. FINDINGS Histopathologic
analysis from
horse cerebral
tissue showed
injury related to
encephalitis and
WNV infection was confirmed by
immunohistochemistry. The
virus was detected by
reverse transcription quantitative
polymerase chain reaction (RT-qPCR) from
brain tissue and subsequently isolated in C6/36
cells. WNV full-length
genome was sequenced showing the isolated
strain belongs to lineage 1a. The molecular clock indicated that Brazilian WNV
strain share the same common ancestor that were circulating in US during 2002-2005. MAIN CONCLUSIONS Here we
report the first isolation of WNV in
Brazil from a
horse with neurologic
disease, which was clustered into lineage 1a with others US WNV
strains isolated in beginning of 2000's decade.