Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 29, 2011
Publication Date: February 1, 2012
Citation: Diel, D.G., Susta, L., Cardenas, S., Brown, C.C., Miller, P.J., Afonso, C.L. 2012. Complete genome and clinic opathological characterization of a virulent Newcastle disease virus isolate from South America. Journal of Clinical Microbiology. 50:378-387. Interpretive Summary: Newcastle disease is one of the most important diseases of poultry, negatively affecting trade and poultry production worldwide. Newcastle disease is caused by Newcastle disease virus also known as avian paramyxovirus type 1. Although all Newcastle disease virus isolates characterized to date belong to the same serological group, there are significant genetic differences between Newcastle disease virus isolates. The genetic differences between Newcastle disease virus isolates have been used to classify these viruses in distinct genetic groups. In this study, a Newcastle disease virus isolate obtained from poultry in Peru, South America, in 2008. Analysis of the sequence of the complete fusion gene of the Peru/08 isolate and comparison of this sequence to other genetic groups, demonstrated that Peru/08 is genetically different from all other known genetic groups. These observations also suggested that Peru/08 may represent a new genetic group. Studies performed in chickens in vivo to investigate the clinical outcome of the infection by the isolate Peru/08 demonstrated that this virus causes a severe and systemic disease, affecting many internal organs of the inoculated birds. The results of our study are in agreement with other studies conducted with Newcastle disease demonstrating the Newcastle disease virus undergoes continuous genetic changes on its genome which may occasionally lead to the appearance of novel and distinct genetic groups. These observations highlight the importance of constant surveillance for Newcastle disease virus and the need for the rapid characterization of the isolates circulating worldwide.
Technical Abstract: Newcastle disease (ND) is one of the most important diseases of poultry, negatively affecting trade and poultry production worldwide. The disease is caused by Newcastle disease virus (NDV) or avian paramyxovirus type-1 (APMV-1), a negative sense single-stranded RNA virus of the genus Avulavirus, family Paramyxoviridae. Although all NDV isolates characterized to date belong to a single serotype of APMV-1, significant genetic diversity has been described between different NDV isolates. Based on the genetic diversity, different NDV isolates have been classified into genotypes. Here we present the characterization of a virulent NDV isolate obtained from poultry in South America, during an outbreak of ND in Peru in 2008. Sequencing and phylogenetic analysis of the complete F gene and of the complete genome demonstrated that NDV-Peru/08 does not group with other known class II genotypes, forming a separate branch in the phylogenetic trees. Analysis of the evolutionary distances between NDV-Peru/08 and established genotypes supported the phylogeny, and further suggested that NDV-Peru/08 may represent a novel genotype within class II. Although NDV-Peru/08 has diverged significantly from other NDV genotypes, pathogenesis studies conducted in chickens revealed that NDV-Peru/08-infection results in characteristic velogenic viscerotropic ND. These findings corroborate with results of other studies demonstrating that NDV is continuously evolving, and further indicate that the genetic changes that occur in the NDV genome may occasionally lead to the emergence of novel genotypes. These observations highlight the importance of constant epidemiological surveillance for NDV and the need for a proactive characterization of the isolates circulating worldwide.