Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 7, 2009
Publication Date: December 8, 2009
Citation: Pantin Jackwood, M.J., Afonso, C.L., Miller, P.J. 2009. Newcastle disease: New challenges in diagnostic and vaccination [abstract]. 44th United States-Japan Cooperative Program in Natural Resources, November 30-December 5, 2009, Tsukuba, Japan. p. 33. Technical Abstract: Since the discovery of Newcastle disease virus (NDV) in 1926, nine genotypes of class I viruses and ten of class II have been identified, representing a diverse and continually evolving group of viruses. The emergence of new virulent genotypes during global epizootics and the year-to¬ year changes observed in NDV of low and high virulence implies that different genotypes of NDV are simultaneously evolving in different geographic locations across the globe. This large genomic diversity together with the high mobility of wild avian hosts creates challenges for vaccination and diagnostics. For example, in the United States, the widely used real-time reverse transcription polymerase chain reaction (RRT-PCR) matrix gene assay for identification of NDV often fails to detect low virulence viruses from waterfowl, while the RRT-PCR fusion gene assay, used to identify virulent isolates, often fails to detect certain virulent NDV genotypes. In addition to biosecurity, prevention of Newcastle disease (ND) includes immunization with inactivated or live ND virus vaccines. Inactivated vaccines are not as effective as live attenuated viruses in inducing a mucosal immune responses and neither prevents virulent viruses from effectively replicating in vaccinated birds and being shed into the environment. The puzzling persistence of virulent NDV in poultry despite continued worldwide vaccination and the emergence of new strains of increased virulence worldwide suggest that vaccination may have failed to prevent the emergence and maintenance of highly virulent forms. Phylogenetic analysis of field samples reveal evidence of evolutionary shift likely caused by vaccination. Furthermore, here we present evidence that current vaccines, which were developed approximately 50 years ago, are not as effective as antigenically matched vaccines in preventing viral replication, shedding and transmission. Different approaches are being used as a solution to this loss in vaccine effectiveness by the improvement of the immunogenic response to NDV based on antigenic matching.