Diagnosis of turkey meningoencephalitis virus infection in field cases by RT-PCR compared to virus isolation in embryonated eggs and suckling mice

Turkey meningoencephalitis (TME) is a paralytic epornitic disease of turkeys caused by turkey meningoencephalitis virus (TMEV), an arthopod-borne flavivirus belonging to the Ntaya serogroup VI. A TMEV specific RT-PCR was compared with classical techniques for TMEV diagnosis, which include virus isolation in 8-day-old chicken embryonated eggs and suckling mice, on 17 TME flocks with neurological signs that occurred during the fall of 1997. In 11/17 flocks both the RT-PCR and the virus isolation methods detected virus, in 4/17 flocks a negative diagnosis was obtained by both methods, and two flocks were positive by RT-PCR only. In four flocks RT-PCR only detected virus after inoculation into embryonated eggs or suckling mice. There was a dose response effect in the yield of the RT-PCR product. Direct examination of turkey brains yielded bands of low to medium intensity. Use of RT-PCR after embryo and/or mouse inoculation resulted in products of far greater intensity. Thus, RT-PCR can be successfully used to amplify TMEV RNA in the brains of diseased turkeys but a negative result would require egg and mouse inoculation for enrichment of virus prior to RT-PCR.