Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2008
Publication Date: 9/1/2008
Citation: Perozo, F., Merino, R., Afonso, C.L., Villegas, P., Calderon, N. 2008. Biological and phylogenic characterization of virulent Newcastle disease virus circulating in Mexico. Avian Diseases. 52(3):472-479.
Interpretive Summary: We have evaluated the biological and pylogenetic characteristics of viruses circulating in Mexico during the period 2001 to 2006. These viruses represent a threat to Mexican and U.S. poultry production because they are highly virulent and circulate in Mexico despite massive vaccination efforts. Although related to viruses of the latest US outbreak they are phylogenetically distinct and likely a product of evolutionary changes created after vaccination was implemented in Mexico.
Technical Abstract: In this report, virulent Newcastle disease viruses (NDVs) isolated in Mexico between 1998 and 2006 were subjected to biological and phylogenetic assessment. Biological characterization using standard pathogenicity tests and phylogenetic analysis were performed. Chicken embryo mean death time (MDT) test results ranged from 39.7 to 61.5 hours and intracerebral pathogenicity index (ICPI) values were between 1.59 and 1.94, respectively, compared to a possible maximum value of 2.0. These isolates showed a dibasic amino acid motif in the fusion protein cleavage site sequence required for host systemic replication. Phylogenetic analysis indicated that the Mexican virulent NDVs belong to the class II, genotype V viruses and can be clearly divided in two groups, isolates from 1998 to 2000, showing a close epidemiological relationship with the latest U.S. outbreaks and viruses isolated from 2004 to 2006, that showed higher virulence and are phylogenetically distinct representing an evolutionary shift that has not yet been detected in the U.S. The assessment of the evolution of viruses from Mexico and other neighboring countries will aid in the U.S surveillance efforts for early detection of highly virulent NDV.