Avian paramyxovirus serotype-1 isolation from migratory birds and environmental water in southern Japan: an epidemiological survey during the 2018/19-2021/2022 winter seasons.

Newcastle disease caused by highly pathogenic viruses of avian paramyxovirus serotype-1 (APMV-1) is a highly contagious poultry disease. Although a large-scale epidemic of Newcastle disease had been occurred in Japan between the 1950s and the 2000s, there have been no outbreak cases anywhere since 2010. In addition, there are no reports of epidemiological surveys of APMV-1 in wild birds in Japan around the last ten years. We conducted the first epidemiological survey of APMV-1 in the Izumi plain, Kagoshima prefecture of southern Japan from the winter of 2018-2022. A total of 15 APMV-1 were isolated, and isolation rates from roosting water and duck fecal samples were 2.51% and 0.10%, respectively. These results indicate that the isolation method from environmental water may be useful for efficient surveillance of APMV-1 in wild birds. Furthermore, this is the first report on success of APMV-1 isolation from environmental water samples. Genetic analysis of the Fusion (F) gene showed that all APMV-1 isolates were closely related to virus strains circulating among waterfowl in Far East Asian countries. All isolates have avirulent motifs in their cleavage site of F genes, indicated that all of which were presumed to be low pathogenic viruses in poultry. However, pathogenicity test using embryonated chicken eggs demonstrated that some isolates killed all chicken embryos regardless of viral inoculated doses (10 2 -10 6 50% egg infectious dose). These results indicated that APMV-1 which are potentially pathogenic to chickens are continuously brought into the Izumi plain by migrating of wild birds. This article is protected by copyright. All rights reserved.