RESUMEN
Newcastle disease is one of the main concerns of poultry farmers. Detection of virulent strains of Newcastle disease virus [NDV] has a great impact on control measures against the disease. In this study RT-PCR was optimized in high sensitivity in order to differentiate the virulent from non-virulent NDV isolates directly in tissue homogenates. The vaccinal NDV strain and known field isolates were tested by this technique. RT-PCR was performed using two sets of primers chosen from a section of the F gene. The PCR product was cloned in to a pTZ57R/T vector and sequenced. The sequence data confirmed the specificity of the test. Detection of viral virulence was determined based on the amplification of PCR products. The above optimized RT-PCR produce can be used to confirm the diagnosis of Newcastle disease within 24 hrs using RNA isolated directly from tissue homogenate or passaged in SPF [Specific Pathogen Free] embryonated eggs