A multiplex reverse transcription polymerase chain reaction (RT-PCR) was developed and optimized to simultaneously detect 3 subtypes (H5, H7 and H9) of avian influenza virus type A. The developed method was specific to amplify only the HA gene of H5, H7 and H9 of Influenza type A and no amplification with other subtypes of AIV and other avian infectious viruses such as Newcastle disease virus, ...