Isolation and molecular characterization of Newcastle disease virus from imported birds at an animal quarantine station in Malaysia

Five Newcastle disease viruses (NDVs) were isolated from imported birds at an animal quarantine station in Malaysia from 2012 to 2017. Analysis of the deduced amino acid sequences of the fusion (F) protein cleavage site showed that all the Newcastle disease virus (NDV) isolates were virulent with the 112RRQ/KKRF117 motif. Phylogenetic analysis of the F gene revealed that four isolates were grouped in genotype VIa while one was in genotype VIIi. Among the four VIa viruses, three were clustered together with the Belgium strain and one with the United States strain. Meanwhile, the VIIi virus was highly similar to the Pakistan strain. VIa viruses in Malaysia were mostly detected from imported avian and there are no currently reported outbreaks caused by this virus. Whereas NDV VIIi viruses caused outbreaks in poultry in Malaysia in 2011 to 2012. There were only slight differences between the F gene of the imported and local existing VIIi viruses. This study revealed the isolation of different genotypes of virulent NDV of different origin from imported birds. As captive birds can transmit NDV across international boundaries and viral transmission between birds and poultry may lead to outbreaks, hence, screening imported birds for diseases is the most crucial step in preventing the spread of this disease. NDV can cause significant economic losses to the poultry industries worldwide. With the increase in international trade of birds and poultry, strict quarantine systems and good laboratory diagnostic capabilities that can characterize and differentiate imported viral strains from existing circulating strains in the country are important in attempts to prevent the entry of foreign viral NDV strains