Detection of Louping ill virus in clinical specimens from mammals and birds using TaqMan RT-PCR

The identification of Louping ill virus (LIV) in clinical specimens has been routinely achieved by virus isolation using susceptible pig kidney cells and subsequent serological analysis. While this method is sensitive and detects infectious virus, it is relatively labour intensive and time-consuming. In view of the veterinary and potential medical importance of LIV, a rapid and precise detection method for routine use that employs the TaqMan reverse transcription polymerase chain reaction (RT-PCR) has been developed to detect LIV RNA extracted from field samples. The TaqMan assay was evaluated against virus isolation using 22 cell culture grown LIV isolates, which had previously been partially characterised by sequencing, and material from 63 suspect field cases. Histopathological and/or serological reports were available for 39 of the suspect cases, providing additional diagnostic information to evaluate the results obtained from the TaqMan RT-PCR assay. The TaqMan assay was as sensitive as the cell culture infectious virus assay currently used and had the advantage that it was able to detect LIV in clinical specimens from which infectious virus could not be isolated possibly due to the presence of high levels of LIV antibody.