Volume 80, Issue 5
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645


During the monitoring of arbovirus seroprevalence in wild birds collected in California, we inadvertently made two isolates of western equine encephalomyelitis virus (WEEV) from California quail sera being tested by plaque reduction neutralization assay for antibodies against St Louis encephalitis (SLEV) and West Nile (WNV) viruses despite heating the sera at 56°C for 30 minutes. These data prompted us to examine the thermostability of these viruses during heat treatment. The flaviviruses, SLEV and WNV, at titers up to 10 plaque-forming units (PFU), were readily inactivated by the standard protocol of heating at 56°C for 30 minutes. In contrast, solutions containing 10 and 10 PFU of WEEV required 2 hours for complete inactivation. Occasional presence of live virus within sera could lead to false negatives using standard plaque reduction neutralization test protocols.


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  • Received : 18 Nov 2008
  • Accepted : 16 Jan 2009
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