| Avian paramyxovirus type 1 (APMV-1) may cause diseases, named differently in different poultry species, including chicken Newcastle disease, goose Paramyxovirus disease, pigeon paramyxovirus type 1 disease. The virulence and pathogenicity of APMV-1 field isolates are different among the poultry species. There is not a technique available for the rapid diagnosis of the disease in all the species and the determination of virulence of the virus at the same time. The results determined by the criteria of virulence and pathogenicity with traditional NDV standard is not identical all the time with facts in the field for all the isolates.The isolation and identification of APMV-1 were performed on the field cases of suspected APMV-1 infection in Guangxi poultry. The virulence and pathogenicity of the representing isolates of different poultry species origin were tested with the conventional standard for Newcastle disease virus (NDV). The results indicated that the mean death time (MDT) and the intracerebral pathogenicity index (ICPI) of isolates gxc2, gxg17, gxg44 were 52h, 53.6h, 36h and 1.80, 1.95, 1.80 respectively, all were classified into highly pathogenic (velogenic); The isolate gxcl classified into velogenic (MDT, 69.6h, ICPI, 1.70); The MDT of isolate gxp22 is 66.8h, would classified into moderately pathogenic (mesogenic), but the ICPI was 0, that were not identical with the serve disease in the field for pigeons.A reverse-transcriptase polymerase chain reaction (RT-PCR) based technique was developed to detect Newcastle disease virus (NDV) of different poultry species origin. Four oligonucleotide primers, based on the differences of nucleotide sequence at the cleavage site of fusion (F) protein gene between virulent and non-virulent strains of APMV-1, were designed to amplify specific DNA fragment from different viruses. The results showed that samples confined non-virulent APMV-1 can yield two bands of 123bp and 362bp, while those of virulent NDV can yield two bands of 254bp and 362bp. The RNA genome of virus used forRT-PCR can be isolated not only from the infected chicken embryonated fluids, but also directly from tissue homogenate of field samples. The detection results of 67 field samples were identical with that of the conventional diagnosis. The results demonstrated that the developed RT-PCR based protocol is a specific, sensitive and rapid diagnostic technique for APMV-1 infections in different poultry species and can also be used to determinate the virulence of the pathogens.The N-terminal nucleotides 47-420 of the Guangxi APMV-1 isolates of different poultry species origin were amplified and sequenced. The alignment and phylogenetic analysis of the nucleotide sequences and deduced amino acid sequences of F gene of the Guangxi isolates and other reference strains obtained from GenBank were done. The results indicate that the nucleotide sequences and deduced amino acid sequences of all the Guangxi isolates in the signal peptides were highly homologous, but lowly homologous with other reference strains. The amino acid composes and arrangement of all Guangxi isolates at the cleavage site has the typical pattern of NDV virulent strains, and is identical with the facts in the field cases. All the Guangxi isolates are classified into genotype VII of APMV-1, the same genotype dominated in China and other areas in recent years. Furthermore, the study also firstly found that Mukteswar, a widely used vaccine strain in China, was classified into genotype VII...
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