Abstract

Isolations of genotype IX (gIX) Avian Paramyxovirus Type 1 (APMV-1) from various bird species have been more common recently, with isolates showing variable pathogenicity in different species of poultry. Here we sequenced the genome of a Muscovy duck origin gIX virus strain XBT14, and characterized the virulence and pathogenicity of this isolate in chickens and ducks. The genome sequence of strain XBT14 is 15192 nt in length, containing multiple basic amino acids at the cleavage site of fusion protein. The strain XBT14 shared 91.6% to 91.9% nucleotide identities with early-genotype viruses (such as genotype III and IV), while shared 85.3% to 85.9% nucleotide homologies to later genotype viruses (such as genotype VII). Pathogenicity tests showed that strain XBT14 could cause death in different duck breeds with mortality rate of 44.4% in Muscovy duck, of 25.9% in Sheldrake, and 11.1% in Cherry Valley duck, respectively. Similar mortality discrepancies were also observed in different ducks when infected with chicken-origin gIX virus strain F48E8. The above results indicate that XBT14-like velogenic gIX APMV-1 (such as XBT14, F48E8 and GD09-2) could cause fatal infection in duck, and genotype IX is a novel genotype that virulent to duck as well as genotype VII did. Accompanied by genetic differences to the vaccine strains or dominant strains prevailing in poultry, the virulent XBT14-like gIX viruses might become potential endemic strains in poultry in the future.

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