First detection and biological characterization of an avian metaavulavirus 8 isolated from a migratory swan goose in Qinghai Lake, Northwest China.

Avian metaavulavirus 8 (AMAV-8), formerly known as avian paramyxovirus 8 (APMV-8), has been detected sporadically in wild birds worldwide since it was first identified in a Canadian goose in 1976. However, the presence of AMAV-8 in birds has never been reported in China. To understand the epidemiological situation of AMAV-8 and its ability to infect chickens, we conducted a surveillance study and in vivo analysis of the AMAV-8 isolate identified in total of 14,909 clinical samples collected from wild and domestic birds from 2014 to 2022 in China. However, in 2017, only one AMAV-8 virus (Y7) was successful isolated from the fresh droppings of a migratory swan goose in Qinghai Lake in Northwest China. Thereafter, we report the complete genome sequence of the Y7 strain with a genome length of 15,342 nucleotides and the Y7 isolate was genetically closely-related to wild bird-origin AMAV-8 viruses previously circulated in the United States, Japan, and Kazakhstan. Furthermore, AMAV-8 infections of one-day-old specific pathogen-free (SPF) chicks did not induce any clinical signs over the entire observation period but was associated with viral shedding for up to 8 days. Interestingly, although all birds infected with the Y7 strain seroconverted within the first week of infection, virus replication was only detected in the trachea but not in other tissues such as the brain, lung, or heart. Here, we report the complete genome, genetic and biological characterization, replication and pathogenicity analysis in vivo and first detection of AMAV-8 in China.