A naturally occurring mutation within the probe-binding region compromises a molecular-based West Nile virus surveillance assay for mosquito pools (Diptera: Culicidae)

Abstract

A naturally occurring mutation was detected within the probe binding region targeting the envelope gene sequence of West Nile virus used in real-time polymerase chain reaction assays to test mosquito pools and other samples. A single C-->T transition 6nt from the 5' end of the 16mer in the envelope gene probe-binding region at genomic position 1,194 reduced assay sensitivity. The mutation first was detected in 2009 and persisted at a low prevalence into 2011. The mutation caused a 0.4% false negative error rate during 2011. These data emphasized the importance of confirmational testing and redundancy in surveillance systems relying on highly specific nucleic acid detection platforms.

Fig. 1

Map of California showing areas where mosquitoes are sampled by local mosquito control districts. Points show years and districts where the mutant WNV was detected in one or more pools based on the relationship between WN2 and WN1 Ct scores. (Online figure in color.)