Phylogenetic and biological characterization of Newcastle disease virus isolates from Pakistan

Authors: KHAN, TASEER - Sindh Poultry Vaccine Center; Rue, Cary; REHMANI, SHAFQAT - Sindh Poultry Vaccine Center; AHMED, AYAZ - Sindh Poultry Vaccine Center; Wasilenko, Jamie; Miller, Patti; Afonso, Claudio

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2010
Publication Date: 5/10/2010
Citation: Khan, T.A., Rue, C.A., Rehmani, S.F., Ahmed, A., Wasilenko, J.L., Miller, P.J., Afonso, C.L. 2010. Phylogenetic and biological characterization of Newcastle disease virus isolates from Pakistan. Journal of Clinical Microbiology. 48(5):1892-1894. DOI: 10.1128/JCM.00148-10.

Interpretive Summary: Virulent Newcastle Disease Virus (NDV) is endemic in Pakistan, it is a major problem to their poultry industry, and has potential for spread worldwide through trade or by wild bird populations. Additionally, since Newcastle Disease is highly contagious and clinically similar to the highly pathogenic avian influenza, accurate and rapid monitoring of an outbreak is very important. Prompt and reliable differentiation of virulent NDV from lentogenic NDV is necessary. Biological and phylogenetic characterization of eight previously uncharacterized NDV isolates from poultry (1995-2008) and two commonly used vaccine strains was performed. The current USDA-validated assay for the fusion gene that is specific for velogenic NDV successfully detected eight uncharacterized poultry isolates from Pakistan. However, the USDA-validated assay for the matrix gene that is designed to detect all NDV isolates did not detect the common vaccine strain used in Pakistan (Mukteswar) nor three of the eight uncharacterized isolates. A new matrix gene test was developed that successfully detects all eight isolates and two vaccine strains (all isolates tested). Phylogenetic analysis revealed that the samples collected during 1995-2005, are more closely related to isolates in genotype IV while isolates from 2006-2008, are group with genotype VII. Intracerebral pathogenicity index (ICPI) test indicates that viruses of both genotypes are likely to be highly virulent. These results indicate that there are multiple genotypes circulating in Pakistan which are causing outbreaks in commercial and backyard poultry.

Technical Abstract: Virulent Newcastle Disease Virus (NDV) is endemic in Pakistan and is a major problem to their poultry industry. Since Newcastle Disease is highly contagious and clinically similar to the highly pathogenic avian influenza, accurate and rapid monitoring of an outbreak is very important. Additionally, prompt differentiation of virulent NDV from lentogenic NDV is necessary. The current USDA-validated assay for the fusion gene that is specific for velogenic NDV successfully detected eight uncharacterized poultry isolates from Pakistan (1995-2008). However the matrix test did not detect the mesogenic vaccine strain used in Pakistan (Mukteswar) nor three of the eight uncharacterized isolates. A new matrix gene test was developed that successfully detects all eight isolates and two vaccine strains (all isolates tested). Phylogenetic analysis revealed that the samples collected during 1995-2005 are more closely related to isolates in genotype IV while isolates from 2006-2008 are group with genotype VII. Intracerebral pathogenicity index (ICPI) test indicates that viruses of both genotypes are likely to be highly virulent. These results indicate that there are multiple genotypes circulating in Pakistan which are causing outbreaks in commercial and backyard poultry.