Background: Newcastle disease viruses (NDVs) can spread across continents via migratory birds. Hence, we investigated the frequency of NDV in both non-migratory and birds migrating on the Black Sea-Mediterranean flyway, in Istanbul, Turkey. Birds were trapped using nets placed around the Kucukcekmece lake Avcilar, Istanbul, in spring seasons of 2016 and 2018. In total, 297 birds belonging to 42 different species were trapped, categorized according to species and sex, and flocked oropharyngeal swabs were collected. In addition, flocked swabs were also collected from 115 mallards caught by hunters around Edirne and from 207 birds which had been treated in the Veterinary Faculty of Istanbul university-Cerrahpasa. Tissue samples were taken from dead wild birds brought by public to Veterinary Faculty. A total of 619 flocked oropharyngeal swabs were pooled into 206 samples. RNA was extracted from swabs and tissue samples. Real-time RT-PCR prob. assay was used to detect NDV-RNA in samples. Results: There was no amplification in real time RT-PCR in samples taken from wild birds caught by traps. However, amplification of NDV-F gene was observed in oropharyngeal swabs taken from 2 waterfowls (Common Moorhen and Mallard), and in tissue samples taken from 2 little owls and 1 common kestrel. Sequencing and phylogenetic analyses of these 5 samples for NDV-F gene showed great similarity with NDV subgenotype VII.2 viruses. Analysis also showed that there is a high similarity with the F gene sequences previously reported from Turkey in 2012 and as well as the sequences from neighbouring countries Bulgaria and Georgia and geographically close country such as Pakistan. Although the strains found in this study are closely related, there is a relatively small degree of molecular divergence within 543 bp of F gene of the Turkish NDV isolate and strains detected in Israel, Pakistan, Iran, United Arab Emirates and Belgium. Conclusions: Our findings revealed the presence of subgenotype VII.2 of NDVs in wild birds in north west of Turkey and demonstrated some degree of molecular evolution when compared to the earlier NDV-VII.2 isolate in Turkey.

Background: Newcastle disease viruses (NDVs) can spread across continents via migratory birds. Hence, we investigated the frequency of NDV in both nonmigratory and birds migrating on the South East European flyway, in Istanbul, Turkey. Birds were trapped using nets placed around the Kucukcekmece lake Avcilar, Istanbul, in spring seasons of 2016 and 2018. In total, 297 birds belonging to 42 different species were trapped, categorised according to species and sex, and oropharyngeal swabs were collected. Swabs from 115 mallards caught by hunters in Edirne and from 207 birds belonging to 31 species which had been treated in the Veterinary Faculty of Istanbul were also collected. Tissue samples were taken from dead wild birds brought by public to Veterinary Faculty of Istanbul. A total of 619 oropharyngeal swabs were pooled into 206 samples. RNA was extracted from the swabs and tissue samples. Real-time RT-PCR prob assay was used to detect NDV-RNA in samples. Results: There was no amplification in real time RT-PCR in samples taken from wild birds caught by traps. However, amplification of NDV-F gene was observed in oropharyngeal swabs taken from 2 waterfowls, and in tissue samples taken from 2 little owls and 1 common kestrel. Sequencing and phylogenetic analyses of these 5 samples for NDV-F gene showed great similarity with NDV lineage VIIi viruses. One (waterfowl) of the five NDV-F gene sequences obtained in this study was slightly different than previously isolated Turkish NDVs and NDVs from Bulgaria and Georgia. Remaining four NDV-F gene sequences were similar to NDVs that were previously isolated in Turkey, Bulgaria and Georgia. Although the strains found in this study are closely related, there is a relatively small degree of molecular divergence within F gene of the Turkish NDVs and strains from Iran Pakistan, Israel and Belgium. Conclusions: Our findings show that first time in Turkey, genotype VIIi of NDVs is predomiant in wild birds in the Eurasia region and some degree of molecular evolution when compared to the earlier NDV-VIIi isolates in Turkey. Also, NDV viruses prevailing in the migratory birds pose a serious risk to poultry in Turkey and other countries.