Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2014
Publication Date: 5/5/2014
Publication URL: http://handle.nal.usda.gov/10113/59859
Citation: Susta, L., Hamal, K.R., Miller, P.J., Garcia, S.C., Brown, C.C., Pedersen, J.C., Gongora, V., Afonso, C.L. 2014. Separate evolution of virulent newcastle disease virus from Mexico and Central America. Journal of Clinical Microbiology. 52(5):1382-1390. DOI: 10.1128/JCM.00066-14. Interpretive Summary: Newcastle disease (ND) is a severe disease of poultry and other avian species, characterized by high morbidity and mortality. It is caused by virulent strains of Newcastle disease virus (NDV). In 2008, a poultry outbreak of ND was reported in Belize, a country in Central America. In this study, three NDV isolates from the Belize outbreak (NDV-Belize-3/08, NDV-Belize-12/08, and NDV-Belize-4/08) were used to infect chickens to view the gross lesions in the organs and the sickness they caused. Our results showed that all three NDV strains had an intra-cerebral pathogenicity index (ICPI) greater than 0.7, and a polybasic amino acid sequence of the fusion protein cleavage site with a phenylalanine at position 117, indicating that these strains are virulent (cause disease) by international standards. NDV-Belize-3/08 behaved as typical velogenic viscerotropic NDV strain in infected chickens, with severe necro-hemorrhagic lesions in the organs important for making antibodies and intestinal tissues, and was found in several organs of the infected birds. Phylogenetic analysis of Fusion gene showed that NDV genotype V (a type of genetic classification)can be divided into three sub-genotypes (Va, Vb, and Vc), and that the three Belize strains all belong to NDV sub-genotype Vb, and are 100% similar to each other. Additionally, these are genetically closely related to “older” Mexican strains isolated from 1988 to 2002 in that country. The lack of any reported isolation of closely related, highly virulent viruses in poultry since 2002 in Belize or other neighboring countries suggests that these viruses may have been circulating in an unknown reservoir before spilling in poultry and causing an outbreak in 2008. The data presented here confirm the circulation of virulent NDV strains in Central America, demonstrating the importance of unknown reservoirs in the epidemiology of NDV for the prevention of ND in both commercial and backyard poultry.
Technical Abstract: A poultry outbreak of Newcastle disease (ND) was reported in Belize in 2008. The characteristics of three virulent Newcastle Disease Virus (NDV) isolates from this outbreak (NDV-Belize-3/08, NDV-Belize-12/08, NDV-Belize-4/08) were assessed by genomic analysis and by clinico-pathological characterization in specific pathogen (SPF) chickens. Results showed that all three strains belong to NDV genotype V and are virulent, as assessed by the intra-cerebral pathogenicity index and the polybasic amino acid sequence at the fusion protein cleavage site. In 4-week-old specific pathogen free (SPF), NDV-Belize-3/08 behaved as a typical velogenic viscerotropic NDV strain, causing severe necro-hemorrhagic lesions in the lymphoid organs with systemic virus distribution. Phylogenetic analysis of multiple NDV genotype V representatives revealed that genotype V can be divided into three sub-genotypes, namely Va, Vb, and Vc, and that all tested Belize isolates belong to sub-genotype Vb. Furthermore, these isolates are nearly identical to a 2007 isolate from Honduras, and appeared to have evolved separately from other contemporary viruses circulating in Mexico, clustering into a new clade within NDV sub-genotype Vb.