Virulent Newcastle disease in Australia: Molecular epidemiological analysis of viruses isolated prior to and during the outbreaks of 1998-2000

Gene sequence analysis of fusion (F) gene cleavage motifs and haemagglutini n-neuraminidase (HN) carboxyl-terminal extension sequences was used to anal yse Newcastle disease viruses (NDV) associated with virulent outbreaks of t he disease which occurred in New South Wales, Australia in 1998-2000. PCR f ragments were amplified directly from diseased tissue or allantoic fluids a nd sequence analyses used for phylogenetic comparisons between these viruse s and Australian reference NDV. F and HN gene sequence comparison showed a strong relationship to sequences derived from endemic Australian NDV rather than those of overseas viruses or wild bird isolates. Prior to notificatio n of the 1998 outbreak, an NDV was isolated from chickens suffering respira tory disease that appeared to be the progenitor virus from which the virule nt virus originated. In turn, these viruses are closely related to two prev iously isolated 'ancestor' viruses that have the same unique HN extension s equence. (C) 2001 Elsevier Science B.V. All rights reserved.