An oligonucleotide probe that distinguishes isolates of low virulence from the more pathogenic strains of Newcastle disease virus.

A synthesized oligonucleotide, termed cleavage probe (NDV-CL), has been designed to complement the cleavage-activation site of the fusion gene of the Texas GB isolate of Newcastle disease virus (NDV). This oligonucleotide probe, 21 bases in length, bound with RNA from velogenic strains of NDV tested in a slot-blot hybridization assay. The probe also recognized RNA from the mesogenic strains used in this assay, although no signal was observed with RNA isolated from lentogenic NDVs or with that from other common avian viruses used as controls. This probe did not recognize RNA from isolates of other paramyxovirus serotypes (PMV-2 or PMV-3) included in this study. The ability of this probe to distinguish lentogenic NDVs, which cause little or no clinical disease, from those strains that may produce severe morbidity and/or mortality suggests a potential use for the probe in a molecular diagnostic assay.